EPA-600/R-94/111
Nay 1994
METHODS FOR THE DETERMINATION
OF METALS
IN ENVIRONMENTAL SAMPLES
SUPPLEMENT I
fMIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
Printed on Recycled Paper
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DISCLAIMER
This manual has been reviewed by the Environmental Monitoring Systems
Laboratory - Cincinnati, U.S. Environmental Protection Agency, and approved
for publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
11
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FOREWORD
Environmental measurements are required to determine the quality of
ambient waters and the character of waste effluents. The Environmental
Monitoring Systems Laboratory - Cincinnati (EMSL-Cincinnati) conducts research
to:
o Develop and evaluate analytical methods to identify and measure the
concentration of chemical pollutants in drinking waters, surface
waters, groundwaters, wastewaters, sediments, sludges, and solid
wastes.
o Investigate methods for the identification and measurement of
viruses, bacteria and other microbiological organisms in aqueous
samples and to determine the responses of aquatic organisms to water
quality.
o Develop and operate a quality assurance program to support the
achievement of data quality objectives in measurements of pollutants
in drinking water, surface water, groundwater, wastewater, sediment
and solid waste.
This supplement to the EMSL-Cincinnati publication, "Methods for the
Determination of Metals in Environmental Samples" was prepared to revise and
place in the Environmental Monitoring Management Council (EMMC) format certain
spectrochemical methods used for metals analyses in regulatory compliance
monitoring programs. Also, included in this supplement is a new method,
Method 200.15 Determination of Metals and Trace Elements in Water by
Ultrasonic Nebulization Inductively Coupled Plasma-Atomic Emission
Spectrometry. This method is intended for analysis of ambient waters with
possible limited use in regulatory compliance monitoring. We are pleased to
provide this updated supplement to the manual and believe that it will be of
considerable value to many public and private laboratories that wish to
determine metals in environmental media for regulatory or other reasons.
Thomas A. Clark, Director
Environmental Monitoring Systems
Laboratory - Cincinnati
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ABSTRACT
This manual includes seven analytical methods four of which are
considered multi-analyte methods, two are single analyte methods, and the
total recoverable sample preparation procedure is given as a separate method
write up. These methods utilize inductively coupled plasma (ICP)/atomic
emission spectrometry (AES), ICP/mass spectrometry (MS), graphite furnace
atomic absorption (GFAA), cold vapor atomic absorption (CVAA), and ion
chromatography (1C). Application of these methods is directed primarily
toward aqueous samples such as wastewater, drinking and ambient waters.
However, procedures for the analysis of solid samples such sludges and soils
also are included in the multi-analyte methods 200.7, 200.8, and 200.9.
IV
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TABLE OF CONTENTS
Method
Number Title Revision Date Page
Disclaimer ii
Foreword i i i
Abstract iv
Acknowledgement vi
Introduction . vii
200.2 Sample Preparation Procedure for 2.8 5/94
Spectrochemical Determination of
Total Recoverable Elements
200.7 Determination of Metals and Trace 4.4 5/94
Elements in Water and Wastes by
Inductively Coupled Plasma-Atomic
Emission Spectrometry
200.8 Determination of Trace Elements in 5.3 5/94
Water and Wastes by Inductively
Coupled Plasma - Mass Spectrometry
200.9 Determination of Trace Elements by 2.2 5/94
Stabilized Temperature Graphite Furnace
Atomic Absorption Spectrometry
200.15 Determination of Metals and Trace 1.2 5/94
Elements in Water by Ultrasonic
Nebulization Inductively Coupled
Plasma-Atomic Emission Spectrometry
218.6 Determination of Dissolved Hexavalent 3.3 5/94
Chromium in Drinking Water,
Groundwater, and Industrial Wastewater
Effluents by Ion Chromatography
245.1 Determination of Mercury in Water by 3.0 5/94
Cold Vapor Atomic Absorption
Spectrometry
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ACKNOWLEDGEMENT
The methods included in this manual have been for the most part prepared
and assembled by former and present staff members of the Inorganic Chemistry
Branch of the Chemistry Research Division, Environmental Monitoring Systems
Laboratory - Cincinnati. However, others have contributed as prime authors or
have provided review comments as a function of work group participation. To
recognize those efforts and give a historical perspective to the method,
listed on the title page of each method are the significant versions of the
method and the persons or groups responsible. Finally, all method authors
and contributors wish to thank William L. Budde, Director of the Chemistry
Research Division, and Thomas A. Clark, Director of the Environmental
Monitoring Systems Laboratory - Cincinnati, for their cooperation and support
during this project.
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INTRODUCTION
Six of the seven methods appearing in this supplement were included in
the first publication of the manual "Determination of Metals in Environmental
Samples", EPA 600 4-91/010, June, 1991. The one new method appearing in this
supplement is Method 200.15, Determination of Metals and Trace Elements in
Water by Ultrasonic Nebulization Inductively Coupled Plasma-Atomic Emission
Spectrometry. Method 200.15 was developed to extend the analytical range of
the ICP-AES technique to lower concentrations. Its usefulness for the
analysis of drinking water is evident by the performance data included in the
method.
Unlike the 1991 manual (EPA 600 4-91/010) which contains 13 methods for a
variety of sample matrices, this supplement is focused more on the analysis of
water and wastes. Its purpose is for use in compliance monitoring of National
Pollution Discharge Elimination System (NPDES) effluents as required under the
Clean Water Act and compliance monitoring of drinking water as required under
the Safe Drinking Water Act. These methods are also useful for the analysis
of ambient waters with the exclusion of marine water.
The methods included in this supplement have been prepared in the format
adopted by the Environmental Monitoring Management Council (EMMC). In this
format method sections are ordered in a specific manner and purpose with the
addition of two new sections on pollution prevention and waste management.
All methods have the same approach to analytical quality control in that
initial demonstration of performance is required prior to method use, and
assessing ongoing laboratory performance is mandatory. However, the required
frequency of demonstration has been lessened and the acceptance control limits
have been widened. Also, the required limits used in assessing recovery data
from fortified matrices have been widened. Where available multi-laboratory
data and regression equations have been included in the methods.
The multi-analyte methods (200.7, 200.8, 200.9, and 200.15) all utilize
the same total recoverable sample digestion procedure that is described in
Method 200.2 as a stand-alone procedure. This procedure also is applicable to
flame atomic absorption determinations. Using a common sample preparation for
all spectrochemical techniques is convenient and can reduce cost of analyses.
Changes to previous versions of specific methods are as follows:
o Cerium has been added to Method 200.7 for correction of potential
spectral interferences
o Titanium has been added as an analyte to Method 200.7
o Mercury has been added to Method 200.8 for the analysis of
drinking water with turbidity of < 1 NTU
o Zinc has been deleted from Method 200.9 because its determination
by the graphite furnace technique is impractical
o Digestion of Method 245.1 mercury calibration standards is no
longer required
Vll
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METHOD 200.2
SAMPLE PREPARATION PROCEDURE FOR SPECTROCHEMICAL
DETERMINATION OF TOTAL RECOVERABLE ELEMENTS
Revision 2.8
EMMC Version
T.D. Martin, E.R. Martin, and S.E. Long (Technology Applications, Inc.) -
Method 200.2, Revision 1.1 (1989)
T.D. Martin, S.E. Long (Technology Applications Inc.), and J.T. Creed -
Method 200.2, Revision 2.3 (1991)
T.D. Martin, J.T. Creed, and C.A. Brockhoff - Method 200.2, Revision 2.8
(1994)
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
200.2-1
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METHOD 200.2
SAMPLE PREPARATION PROCEDURE FOR SPECTROCHEMICAL DETERMINATION
OF TOTAL RECOVERABLE ELEMENTS
1.0 SCOPE AND APPLICATION
1.1 This method provides sample preparation procedures for the
determination of total recoverable analytes in groundwaters, surface
waters, drinking waters, wastewaters, and, with the exception of
silica, in solid type samples such as sediments, sludges and soils.1
Aqueous samples containing suspended or particulate material > 1% (W/V)
should be extracted as a solid type sample. This method is applicable
to the following analytes:
Analyte
Chemical Abstract Services
Registry Numbers (CASRN)
Aluminum
Antimony
Arsenic
Boron
Barium
Beryl 1 i urn
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Phosphorus
Potassium
Selenium
Silica9
Silver
Sodium
Strontium
(Al)
(Sb)
(As)
(B)
(Ba)
(Be)
(Cd)
(Ca)
(Cr)
(Co)
(Cu)
(Fe)
(Pb)
(Li)
(Mg)
(Mn)
(Hg)
(Mo)
(Ni)
(P)
(K)
(Se)
(Si02)
(Ag)
(Na)
(Sr)
7429-90-5
7440-36-0
7440-38-2
7440-42-8
7440-39-3
7440-41-7
7440-43-9
7440-70-2
7440-47-3
7440-48-4
7440-50-8
7439-89-6
7439-92-1
7439-93-2
7439-95-4
7439-96-5
7439-97-6
7439-98-7
7440-02-0
7723-14-0
7440-09-7
7782-49-2
7631-86-9
7440-22-4
7440-23-5
7440-24-6
(continues on next page)
This method is not suitable for the determination of silica in solids.
200.2-2
Revision 2.8 May 1994
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Chemical Abstract Services
Analyte Registry Numbers (CASRN)
Thallium
Thorium
Tin
Uranium
Vanadium
Zinc
(Tl)
(Th)
(Sn)
' (U)
(V)
(Zn)
7440-28-0
7440-29-1
7440-31-5
7440-61-1
7440-62-2
7440-66-6
1.2 For reference where this method is approved for use in compliance
monitoring programs [e.g., Clean Water Act (NPDES) or Safe Drinking
Water Act (SDWA)] consult both the appropriate sections of the Code of
Federal Regulation (40 CFR Part 136 Table IB for NPDES, and Part 141
§ 141.23 for drinking water), and the latest Federal Register
announcements.
1.3 Samples prepared by this method can be analyzed by the following
methods given in this supplement: Method 200.7, Determination of
Metals and Trace Elements by Inductively Coupled Plasma-Atomic
Emission Spectrometry; Method 200.8, Determination of Trace Elements
By Inductively Coupled Plasma-Mass Spectrometry; and Method 200.9,
Determination of Trace Elements by Stabilized Temperature Graphite
Furnace Atomic Absorption Spectrometry. Also, this method can be used
prior to analysis by direct aspiration flame atomic absorption for
the above list of analytes with the exception of the following: As, B
Hg, P, Se, Si02, Th, and U.
1.4 The preparation procedures described in this method are not
recommended prior to analysis by the conventional graphite furnace
technique, commonly refered to as "off-the-wall", non-platform or
non-delayed atomization. It is believed that the resulting chloride
concentration in the prepared solutions can cause either analyte
volatilization loss prior to atomization or an unremediable chemical
vapor state interference for some analytes when analyzed using the
conventional graphite furnace technique.
1.5 This method is suitable for preparation of aqueous samples containing
silver concentrations up to 0.1 mg/L. For the analysis of wastewater
samples containing higher concentrations of silver, succeeding smaller
volume, well mixed aliquots must be prepared until the analysis
solution contains < 0.1 mg/L silver. The extraction of solid samples
containing concentrations of silver > 50 mg/kg should be treated in a
similar manner. Also, the extraction of tin from solid samples should
be prepared again using aliquots < 1 g when determined sample
concentrations exceed 1%.
1.6 When using this method for determination of boron and silica in
aqueous samples, only plastic or quartz labware should be used from
200.2-3 Revision 2.8 May 1994
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the time of sample collection to the completion of the analysis. For
accurate determinations of boron in solid samples only quartz or PTFE
beakers should be used during acid extraction with immediate transfer
of an extract aliquot to a plastic centrifuge tube following dilution
of the extract to volume. When possible, borosilicate glass should be
avoided to prevent contamination of these analytes.
1.7 This method will solubilize and hold in solution only minimal
concentrations of barium in the presence of free sulfate. For the
analysis of barium in samples having varying and unknown
concentrations of sulfate, analysis should be completed as soon as
possible after sample preparation.
1.8 This method is not suitable for the determination of volatile low
boiling point organo-mercury compounds.
2.0 SUMMARY OF METHOD
2.1 Solid and aqueous samples are prepared in a similar manner for
analysis. Nitric and hydochloric acids are dispensed into a beaker
containing an accurately weighed or measured, well mixed, homogeneous
aqueous or solid sample. Aqueous samples are first reduced in volume
by gentle heating. Then, metals and toxic elements are extracted from
either solid samples or the undissolved portion of aqueous samples by
covering the beaker with a watch glass and refluxing the sample in the
dilute acid mixture for 30 min. After extraction, .the solubilzed
analytes are diluted to specified volumes with ASTM type I water,
mixed and either centrifuged or allowed to settle overnight before
analysis. Diluted samples are to be analyzed by the appropriate mass
and/or atomic spectrometry methods as soon as possible after
preparation.
3.0 DEFINITIONS
3.1 Field Reagent Blank (FRB) - An aliquot of reagent water or other blank
matrix that is placed in a sample container in the laboratory and
treated as a sample in all respects, including shipment to the
sampling site, exposure to the sampling site conditions, storage,
preservation, and all analytical procedures. The purpose of the FRB
is to determine if method analytes or other interferences are present
in the field environment (Sect 8.3).
3.2 Solid Sample - For the purpose of this method, a sample taken from
material classified as either soil, sediment or sludge.
3.3 Total Recoverable Analyte - The concentration of analyte determined to
be in either a solid sample or an unfiltered aqueous sample following
treatment by refluxing with hot dilute mineral acid.
3.4 Water Sample - For the purpose of this method, a sample taken from one
of the'following sources: drinking, surface, ground, storm runoff,
industrial or domestic wastewater.
200.2-4 Revision 2.8 May 1994
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4.0 INTERFERENCES
4.1 In sample preparation, contamination is of prime concern. The work
area, including bench top and fume hood, should be periodically
cleaned in order to eliminate environmental contamination.
4.2 Chemical interferences are matrix dependent and cannot be documented
previous to analysis.
4.3 Boron and silica from the glassware will grow into the sample solution
during and following sample processing. For critical determinations
of boron and silica, only quartz and/or PTFE plastic labware should be
used. When quartz beakers are not available for extraction of solid
samples, to reduce boron contamination, immediately transfer an
aliquot of the diluted extract to a plastic centrifuge tube for
storage until time of analysis. A series of laboratory reagent blanks
can be used to monitor and indicate the contamination effect.
5.0 SAFETY
5.1 All personnel handling environmental samples known to contain or to
have been in contact with human waste should be immunized against
known disease causative agents.
5.2 The acidification of sample/containing reactive materials may result
in the release of toxic gases, such as cyanides or sulfides.
Acidification of samples should be done in a fume hood.
5.3 Material safety data sheets for all chemical reagents should be
available to and understood by all personnel using this method.
Specifically, concentrated hydrochloric acid and concentrated nitric
acid are moderately toxic and extremely irritating to skin and mucus
membranes. Use these reagents in a hood whenever possible and if eye
or skin contact occurs, flush with large volumes of water. Always
wear safety glasses or a shield for eye protection when working with
these reagents. ''
6.0 EQUIPMENT AND SUPPLIES
6.1 Analytical balance, with capability to measure to 0.1 mg, for use in
weighinglsolids, and for determining dissolved solids in extracts.
6.2 Single pan balance, with capability of weighing to 0.01 g, for use in
rapid weighing solids and liquids or samples in excess of 10 g.
6.3 A temperature adjustable hot plate capable of maintaining a
temperature of 95°C.
6.4 '(optional) A temperature adjustable block digester capable of
(maintaining a temperature of 95°C and equipped with 250-mL constricted
digestion tubes.
200.2-5 Revi si on 2.8 May 1994
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6.5
(optional)
and brake.
A steel cabinet centrifuge with guard bowl, electric timer
6.6 A gravity convection drying oven with thermostatic control capable of
maintaining 180°C ± 5°C.
6.7 (optional) An air displacement pipetter capable of delivering volumes
ranging from 0.1 to 2500 /j|_ with an assortment of high quality
disposable pipet tips.
6.8 Mortar and pestle, ceramic or nonmetallic material.
6.9 Polypropylene sieve, 5-mesh (4 mm opening).
6.10 LABWARE - For determination of trace levels of elements, contamination
and loss are of prime consideration. Potential contamination sources
include improperly cleaned laboratory apparatus and general
contamination within the laboratory environment from dust, etc. A
clean laboratory work area designated for trace element sample
handling must be used. Sample containers can introduce positive and
negative errors in the determination of trace elements by (1)
contributing contaminants through surface desorption or leaching, (2)
depleting element concentrations through adsorption processes. All
reusable labware (glass, quartz, polyethylene, PTFE, FEP, etc.) should
be sufficiently clean for the task objectives. Several procedures
found to provide clean labware include soaking overnight and
thoroughly washing with laboratory-grade detergent and water, rinsing
with tap water, and soaking for four hours or more in 20% (V/V) nitric
acid or a mixture of dilute nitric and hydrochloric acid (1+2+9),
followed by rinsing with ASTM Type I grade water and storing clean.
NOTE: Chromic acid must not be used for cleaning glassware.
6.10.1 Glassware - Volumetric flasks, graduated cylinders, funnels
and centrifuge tubes (glass and/or metal free plastic).
6.10.2 Assorted calibrated pipettes.
6.10.3 Conical Phillips beakers (Corning 1080-250 or equivalent),
250-mL with 50-mm watch glasses.
6.10.4 Griffin beakers, 250-mL with 75-mm watch glasses and
(optional) 75-mm ribbed watch glasses.
6.10.5 (optional) PTFE and/or quartz beakers, 250-mL with PTFE
covers.
6.10.6 Evaporating dishes or high-form crucibles, porcelain, 100 mL
capacity. >
6.10.7 Wash bottle - One piece stem, Teflon FEP bottle with Tefzel
ETFE screw closure, 125-mL capacity.
200.2-6
Revision 2.8 May 1994
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7.0 REAGENTS AND STANDARDS
7.1 Reagents may contain elemental impurities which might affect
analytical data. High-purity reagents should be used whenever
possible. All acids used for this method must be of ultra high-purity
y r*3QQ *
7.1.1 Nitric acid, concentrated (sp.gr. 1.41).
7.1.2 Nitric acid (1+1) - Add 500 ml cone, nitric acid to 400 mL of
ASTM type I water and dilute to 1 L.
7.1.3 Hydrochloric acid, concentrated (sp.gr. 1.19).
7.1.4 Hydrochloric acid (1+1) - Add 500 ml cone, hydrochloric acid
to 400 ml of ASTM type I water and dilute to 1 L.
7.1.5 Hydrochloric acid (1+4) - Add 200 ml cone, hydrochloric acid
to 400 ml of ASTM type I water and dilute to 11.
7.2 Reagent water - For all sample preparation and dilutions, ASTM type I
water (ASTM D1193)3 is required. Suitable water may be prepared by
passing distilled water through a mixed bed of anion and cation
exchange resins.
7.3 Refer to the appropriate analytical method for the preparation of
standard stock solutions, calibration standards, and quality control
solutions.
8.0 SAMPLE COLLECTION. PRESERVATION. AND STORAGE
8.1 For determination of total recoverable elements in aqueous samples,
the samples must be acid preserved prior to aliquoting for either-
sample processing or determination by direct spectrochemical analysis
For proper preservation samples are not filtered, but acidified with
(1+1) nitric acid to pH < 2. Preservation may be done at the time of
sample collection, however, to avoid the hazards of strong acids in
the field, transport restrictions, and possible contamination it is
recommended that the samples be returned to the laboratory within two
weeks of collection and acid preserved upon receipt in the laboratory
Following acidification, the sample should be mixed and held for
sixteen hours. (Normally, 3 ml of (1+1) nitric acid per liter of
sample is sufficient for most ambient and drinking water samples)
The pH of all aqueous samples must be tested immediately prior to
withdrawing an aliquot for processing to ensure the sample has been
properly preserved. If for some reason such as high alkalinity the
sample pH is verified to be > 2, more acid must be added and the
sample held for sixteen hours until verified to be pH < 2 If
properly acid preserved, the sample can be held up to 6 months before
analysis.
NOTE: When the nature of the sample is either unknown or is known to
be hazardous, acidification should be done in a fume hood
See Section 5.2.
200.2-7 Revision 2.8 May 1994
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8.2 Solid samples require no preservation prior to analysis other than
storage at 4°C. There is no established holding time limitation for
solid samples.
8.3 For aqueous samples, a field blank should be prepared and analyzed as
required by the data user. Use the same container and acid as used in
sample collection.
9.0 QUALITY CONTROL
9.1 Each laboratory determining total recoverable elements is required to
operate a formal quality control (QC) program. The minimum
requirements of a QC program consist of an initial demonstration of
laboratory capability, and the analysis of laboratory reagent blanks,
fortified blanks and quality control samples as a continuing check on
performance. The laboratory is required to maintain performance
records that define the quality of data generated.
9.2 Specific instructions on accomplishing the described aspects of the QC
program are discussed in the analytical methods (Sect. 1.3).
10. CALIBRATION AND STANDARDIZATION
10.1 Not applicable. Follow instructions given in the analytical method
selected.
11.0 PROCEDURE
11.1 Aqueous Sample Preparation - Total Recoverable Analytes
11.1.1 For the determination of total recoverable analytes in aqueous
samples, transfer a 100 ml (± 1 ml) aliquot from a well mixed,
acid preserved sample to a 250-mL Griffin beaker (Sects. 1.2,
1.5, 1.6, 1.7, & 1.8). (When necessary, smaller sample aliquot
volumes may be used.)
NOTE: If the sample contains undissolved solids > 1%, a well
mixed, acid preserved aliquot containing no more than
1 g particulate material should be cautiously
evaporated to near 10 ml and extracted using the acid-
mixture procedure described in Sections 11.2.3 thru
11.2.8.
11.1.2 Add 2 ml (1+1) nitric acid and 1.0 ml of (1+1) hydrochloric
acid to the beaker containing the measured volume of sample.
Place the beakeE on the hot plate for solution evaporation.
The hot plate should be located in a fume hood and previously
adjusted to provide evaporation at a temperature of
approximately but no higher than 85°C. (See the following
note.) The beaker should be covered with an elevated watch
glass or other necessary steps should be taken to prevent
sample contamination from the fume hood environment.
200.2-8 Revi si on 2.8 May 1994
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NOTE: For proper heating adjust the temperature control of
the hot plate such that an uncovered Griffin beaker
containing 50 mi of water placed in the center of the
hot plate can be maintained at a temperature
approximately but no higher than 85°C. (Once the beaker
is covered with a watch glass the temperature of the
water will rise to approximately 95°C.)
11.1.3 Reduce the volume of the sample aliquot to about 20 ml by
gentle heating at 85°C. DO NOT BOIL. This step takes about
2 h for a 100 mi aliquot with the rate of evaporation rapidly
increasing as the sample volume approaches 20 ml. (A spare
beaker containing 20 ml of water can be used as a gauge.)
11.1.4 Cover the lip of the beaker with a watch glass to reduce
additional evaporation and gently reflux the sample for 30
minutes. (Slight boiling may occur, but vigorous boiling must
be avoided to prevent loss of the HC1-H20 azeotrope.)
11.1.5 Allow the beaker to cool. Quantitatively transfer the sample
solution to a 50-mi volumetric flask, make to volume with
reagent water, stopper and mix.
11.1.6 Allow any undissolved material to settle overnight, or
centrifuge a portion of the prepared sample until clear. (If
after centrifuging or standing overnight the sample contains
suspended solids that would clog the nebulizer, a portion of
the sample may be filtered for their removal prior to
analysis. However, care should be exercised to avoid
potential contamination from filtration.) The sample is now
ready for analysis by either inductively coupled plasma-atomic
emission spectrometry or direct aspiration flame and
stabilized temperature graphite furnace atomic absorption
spectroscopy (Sects. 1.3 & 1.4).
11.1.7 To ready the sample for analyses by inductively coupled
plasma-mass spectrometry (Sect. 1.3), adjust the chloride
concentration by pipetting 20 ml of the prepared solution into
a 50-mL volumetric flask, dilute to volume with reagent water
and mix. (If the dissolved solids in this solution are >
0.2%, additional dilution may be required to prevent clogging
of the extraction and/or skimmer cones. Internal standards
are added at the time of analysis.)
1.1.1.8 Because the effects of various matrices on the stability of
diluted samples cannot be characterized, all analyses should
be performed as soon as possible after the completed
preparation.
11.2 Solid Sample Preparation - Total Recoverable Analytes
11.2.1 For the determination of total recoverable analytes in solid
samples, mix the sample thoroughly and transfer a portion
200.2-9 Revision 2.8 May 1994
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(> 20 g) to tared weighing dish, weigh the sample and record
the wet weight. (For samples with < 35% moisture a 20 g
portion is sufficient. For samples with moisture > 35% a
larger aliquot 50-100 g is required.) Dry the sample to a
constant weight at 60°C and record the dry weight for
calculation of percent solids (Sect. 12.1). (The sample is
dried at 60°C to prevent the loss of mercury and other
possible volatile metallic compounds, to facilitate sieving,
and to ready the sample for grinding.)
11.2.2 To achieve homogeneity, sieve the dried sample using a 5-mesh
polypropylene sieve and grind in a mortar and pestle. (The
sieve, mortar and pestle should be cleaned between samples.)
From the dried, ground material weigh accurately a
representative 1.0 ± 0.01 g aliquot (W) of the sample and
transfer to a 250-mL Phillips beaker for acid extraction
(Sects. 1.5, 1.6, 1.7, & 1.8).
11.2.3 To the beaker add 4 ml of (1+1) HN03 and 10 ml of (1+4) HC1.
Cover the lip of the beaker with a watch glass. Place the
beaker on a hot plate for reflux extraction of the analytes.
The hot plate should be located in a fume hood and previously
adjusted to provide a reflux temperature of approximately
95°C. (See the following note.)
NOTE: For proper heating adjust the temperature control of
the hot plate such that an uncovered Griffin beaker
containing 50 mL of water placed in the center of the
hot plate can be maintained at a temperature
approximately but no higher than 85°C. (Once the beaker
is covered with a watch glass the temperature of the
water will rise to approximately 95°C.) Also, a block
digester capable of maintaining a temperature of 95°C
and equipped with 250-mL constricted volumetric
digestion tubes may be substituted for the hot plate
and conical beakers in the extraction step.
11.2.4 Heat the sample and gently reflux for 30 min. Very slight
boiling may occur, however vigorous boiling must be avoided to
prevent loss of the HC1-H20 azeotrope. Some solution
evaporation will occur (3 to 4 ml).
11.2.5 Allow the sample to cool and quantitatively transfer the
extract to a 100-mL volumetric flask. Dilute to volume with
reagent water, stopper and mix.
11.2.6 Allow the sample extract solution to stand overnight to
separate insoluble material or centrifuge a portion of the
sample solution until clear. (If after centrifuging or
standing overnight the extract solution contains suspended
solids that would clog the nebulizer, a portion of the extract
solution may be filtered for their removal prior to analysis.
However, care should be exercised to avoid potential
contamination from filtration.) The sample is now ready for
200.2-10 Revision 2.8 May 1994
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analysis by either inductively coupled plasma-atomic emission
spectrometry or direct aspiration flame and stabilized
temperature graphite furnace atomic absorption spectroscooy
(Sects. 1.3 & 1.4).
11.2.7 To ready the sample for analyses by inductively coupled
plasma-mass spectrometry (Sect. 1.3), adjust the chloride
concentration by pipetting 10 ml of the prepared solution into
a 50-mL volumetric flask, dilute to volume with reagent water
and mix. (If the dissolved solids in this solution are >
0.2%, additional dilution may be required to prevent clogging
of the extraction and/or skimmer cones. Internal standards
are added at the time of analysis.)
11.2.8 Because the effects of various matrices on the stability of
diluted samples cannot be characterized, all analyses should
be performed as soon as possible after the completed
preparation.
11.3 Sample Analysis - Use an analytical method listed in Sect. 1.3.
12.0 DATA ANALYSIS AND CALCULATIONS
12.1 To report percent solids in solid samples (Sect. 11.2) calculate as
follows:
DW
% solids (S) = —— x 10
WW
where: DW = Sample weight (g) dried at 60°C
WW = Sample weight (g) before drying
NOTE: If the data user, program or laboratory requires that the
reported percent solids be determined by drying at 105°C,
repeat the procedure given in Section 11.2.1 using a separate
portion (> 20 g) of the sample and dry to constant weight at
103-105°C.
12.2 Calculation and treatment of determined analyte data are discussed in
analytical methods listed in Sect. 1.3.
13.0 METHOD PERFORMANCE
13.1 Not applicable. Available data included in analytical methods listed
in Sect. 1.3.
14.0 POLLUTION PREVENTION
14.1 Pollution prevention encompasses any technique that reduces or
eliminates the quantity or toxicity of waste at the point of
generation. Numerous opportunities for pollution prevention exist in
laboratory operation. The EPA has established a preferred hierarchy
of environmental management techniques that places pollution
200.2-11 Revision 2.8 May 1994
-------
prevention as the management option of first choice. Whenever
feasible, laboratory personnel should use pollution prevention
techniques to address their waste generation. When wastes cannot be
feasibly reduced at the source, the Agency recommends recycling as the
next best option.
14.2 For information about pollution prevention that may be applicable to
laboratories and research institutions, consult Less is Better:
Laboratory Chemical Management for Waste Reduction, available from the
American Chemical Society's Department of Government Relations and
Science Policy, 1155 16th Street N.W., Washington D.C. 20036,
(202)872-4477.
15.0 WASTE MANAGEMENT
15.1 The Environmental Protection Agency requires that laboratory waste
management practices be conducted consistent with all applicable rules
and regulations. The Agency urges laboratories to protect the air,
water, and land by minimizing and controlling all releases from hoods
and bench operations, complying with the letter and spirit of any
sewer discharge permits and regulations, and by complying with all
solid and hazardous waste regulations, particularly the hazardous
waste identification rules and land disposal restrictions. For
further information on waste management consult The Waste Management
Manual for Laboratory Personnel, available from the American Chemical
Society at the address listed in the Section 14.2.
16.0 REFERENCES
1. Martin, T.D. and E.R. Martin, "Evaluation of Method 200.2 Sample
Preparation Procedure for Spectrochemical Analyses of Total
Recoverable Elements," December 1989, U.S. Environmental Protection
Agency, Office of Research and Development, Environmental Monitoring
Systems Laboratory, Cincinnati, Ohio 45268.
2. "OSHA Safety and Health Standards, General Industry," (29 CFR 1910),
Occupational Safety and Health Administration, OSHA 2206, revised
January 1976.
3. "Safety in Academic Chemistry Laboratories," American Chemical Society
Publication, Committee on Chemical Safety, 3rd Edition, 1979.
4. "Proposed OSHA Safety and Health Standards, Laboratories,"
Occupational Safety and Health Administration, Federal Register, July
24, 1986.
5. Annual Book of ASTM Standards, Volume 11.01.
200.2-12 Revision 2.8 May 1994
-------
METHOD 200.7
DETERMINATION OF METALS AND TRACE ELEMENTS IN WATER
AMD WASTES BY INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY
Revision 4.4
EMMC Version
USEPA-ICP Users Group (Edited by T.D. Martin and J.F. Kopp) - Method 200 7
Revision 1.0, (Printed 1979, Published 1982)
T.D. Martin and E.R. Martin - Method 200.7, Revision 3.0 (1990)
^
-rn.0^' Brockhoff> J-T. Creed, and EMMC Methods Work Group - Method
^00.7, Revision 4.4 (1994)
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
200.7-1
-------
METHOD 200.7
DETERMINATION OF METALS AND TRACE ELEMENTS IN WATER AND WASTES BY INDUCTIVELY
COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY
1.0 SCOPE AND APPLICATION
1.1 Inductively coupled plasma-atomic emission spectrometry (ICP-AES) is
used to determine metals and some nonmetals in solution. This method
is a consolidation of existing methods for water, wastewater, and
solid wastes.1"4 (For analysis of petroleum products see references
5 and 6 Sect. 16.0) This method is applicable to the following
analytes:
Analyte
Chemical Abstract Services
Registry Numbers (CASRN)
Aluminum
Antimony
Arsenic
Bari urn
Beryl 1 i urn
Boron
Cadmium
Calcium
Ceri uma
Chromium
Cobalt
Copper
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Phosphorus
Potassium
Selenium
Silicab
(continues on
(Al)
(Sb)
(As)
(Ba)
(Be)
(B)
(Cd)
(Ca)
(Ce)
(Cr)
(Co)
(Cu)
(Fe)
(Pb)
(Li)
(Mg)
(Mn)
(Hg)
(Mo)
(Ni)
(P)
(K)
(Se)
(Si02)
next page)
7429-90-5
7440-36-0
7440-38-2
7440-39-3
7440-41-7
7440-42-8
7440-43-9
7440-70-2
7440-45-1
7440-47-3
7440-48-4
7440-50-8
7439-89-6
7439-92-1
7439-93-2
7439-95-4
7439-96-5
7439-97-6
7439-98-7
7440-02-0
7723-14-0
7440-09-7
7782-49-2
7631-86-9
a Cerium has been included as method analyte
potential interelement spectral interference.
for correction of
b This method
solids.
is not suitable for the determination of silica in
200.7-2
Revision 4.4 May 1994
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Chemical Abstract Services
Analyte Registry Numbers (CASRN)
Silver
Sodium
Strontium
Thallium
Tin
Titanium
Vanadium
Zinc
(Ag)
(Na)
(Sr)
(Tl)
(Sn)
(Ti)
(V)
(Zn)
7440-22-4
7440-23-5
7440-24-6
7440-28-0
7440-31-5
7440-32-6
7440-62-2
7440-66-6
1.2 For reference where this method is approved for use in compliance
monitoring programs [e.g., Clean Water Act (NPDES) or Safe Drinking
Water Act (SDWA)] consult both the appropriate sections of the Code of
Federal Regulation (40 CFR Part 136 Table IB for NPDES, and Part 141
§ 141.23 for drinking water), and the latest Federal Register
announcements.
1.3 ICP-AES can be used to determine dissolved analytes in aqueous samples
after suitable filtration and acid preservation. To reduce potential
interferences, dissolved solids should be < 0.2% (w/v) (Sect. 4.2).
1.4 With the exception of silver, where this method is approved for the
determination of certain metal and metalloid contaminants in drinking
water, samples may be analyzed directly by pneumatic nebulization
without acid digestion if the sample has been properly preserved with
acid and has turbidity of < 1 NTU at the time of analysis. This total
recoverable determination procedure is referred to as "direct
analysis". However, in the determination of some primary drinking
water metal contaminants, preconcentration of the sample may be
required prior to analysis in order to meet drinking water acceptance
performance criteria (Sects. 11.2.2 thru 11.2.7).
1.5 For the determination of total recoverable analytes in aqueous and
solid samples a digestion/extraction is required prior to analysis
when the elements are not in solution (e.g., soils, sludges, sediments
and aqueous samples that may contain particulate and suspended
solids). Aqueous samples containing suspended or particulate material
> 1% (w/v) should be extracted as a solid type sample.
1.6 When determining boron and silica in aqueous samples, only plastic,
PTFE or quartz labware should be used from time of sample collection
to completion of analysis. For accurate determination of boron in
solid samples only quartz or PTFE beakers should be used during acid
extraction with immediate transfer of an extract aliquot to a plastic
centrifuge tube following dilution of the extract to volume. When
possible, borosilicate glass should be avoided to prevent
contamination of these analytes.
200.7-3 Revision 4.4 May 1994
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1.7 Silver is only slightly soluble in the presence of chloride unless
there is a sufficient chloride concentration to form the soluble
chloride complex. Therefore, low recoveries of silver may occur in
samples, fortified sample matrices and even fortified blanks if
determined as a dissolved analyte or by "direct analysis" where the
sample has not been processed using the total recoverable mixed acid
digestion. For this reason it is recommended that samples be digested
prior to the determination of silver. The total recoverable sample
digestion procedure given in this method is suitable for the
determination of silver in aqueous samples containing concentrations
up to 0.1 mg/L. For the analysis of wastewater samples containing
higher concentrations of silver, succeeding smaller volume, well mixed
aliquots should be prepared until the analysis solution contains < 0.1
mg/L silver. The extraction of solid samples containing
concentrations of silver > 50 mg/kg should be treated in a similar
manner. Also, the extraction of tin from solid samples should be
prepared again using aliquots < 1 g when determined sample
concentrations exceed 1%..
1.8 The total recoverable sample digestion procedure given in this method
will solubilize and hold in solution only minimal concentrations of
barium in the presence of free sulfate. For the analysis of barium in
samples having varying and unknown concentrations of sulfate, analysis
should be completed as soon as possible after sample preparation.
1.9 The total recoverable sample digestion procedure given in this method
is not suitable for the determination of volatile organo-mercury
compounds. However, if digestion is not required (turbidity < 1 NTU),
the combined concentrations of inorganic and organo-mercury in
solution can be determined by "direct analysis" pneumatic nebulization
provided the sample solution is adjusted to contain the same mixed
acid (HN03 + HC1) matrix as the total recoverable calibration
standards and blank solutions.
1.10 Detection limits and linear ranges for the elements will vary with the
wavelength selected, the spectrometer, and the matrices. Table 1
provides estimated instrument detection limits for the listed
wavelengths.7 However, actual method detection limits and linear
working ranges will be dependent on the sample matrix,
instrumentation, and selected operating conditions.
1.11 Users of the method data should state the data-quality objectives
prior to analysis. Users of the method must document and have on file
the required initial demonstration performance data described in
Section 9.2 prior to using the method for analysis.
2.0 SUMMARY OF METHOD
2.1 An aliquot of a well mixed, homogeneous aqueous or solid sample is
accurately weighed or measured for sample processing. For total
recoverable analysis of a solid or an aqueous sample containing
undissolved material, analytes are first solubilized by gentle
refluxing with nitric and hydrochloric acids. After cooling, the
sample is made up to volume, is mixed and centrifuged or allowed to
200.7-4 Revision 4.4 May 1994
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settle overnight prior to analysis. For the determination of
dissolved analytes in a filtered aqueous sample aliquot, or for the
"direct analysis" total recoverable determination of analytes in
drinking water where sample turbidity is < 1 NTU, the sample is made
ready for analysis by the appropriate addition of nitric acid, and
then diluted to a predetermined volume and mixed before analysis.
2.2 The analysis described in this method involves multielemental
determinations by ICP-AES using sequential or simultaneous
instruments. The instruments measure characteristic atomic-line
emission spectra "by optical spectrometry. Samples are nebulized and
the resulting aerosol is transported to the plasma torch. Element
specific emission spectra are produced by a radio-frequency
inductively coupled plasma. The spectra are dispersed by a. .grating
spectrometer, and the intensities of the line spectra are monitored at
specific wavelengths by a photosensitive device. Photocurrents from
the photosensitive device are processed and controlled by a computer
system. A background correction technique is required to compensate
for variable background contribution to the determination of the
analytes. Background must be measured adjacent to the analyte
wavelength during analysis. Various interferences must be considered
and addressed appropriately as discussed in Sections 4, 7, 9, 10, and
Jl X •
3.0 DEFINITIONS
3.1 Calibration Blank - A volume of reagent water acidified with the same
acid matrix as in the calibration standards. The calibration blank is
a zero standard and is used to calibrate the ICP instrument (Sect.
7.10.1).
3.2 Calibration Standard (CAL) - A solution prepared from the dilution of
stock standard solutions. The CAL solutions are used to calibrate the
instrument response with respect to analyte concentration (Sect. 7.9).
3.3 Dissolved Analyte - The concentration of analyte in an aqueous sample
that will pass through a 0.45-//m membrane filter assembly prior to
sample acidification (Sect. 11.1).
3.4 Field Reagent Blank (FRB) - An aliquot of reagent water or other blank
matrix that is placed in a sample container in the laboratory and
treated as a sample in all respects, including shipment to the
sampling site, exposure to the sampling site conditions, storage,
preservation, and all analytical procedures. The purpose of the FRB
is to determine if method analytes or other interferences are present
in the field environment (Sect 8.5).
3.5 Instrument Detection Limit (IDL) - The concentration equivalent to the
analyte signal which is equal to three times the standard deviation of
a series of ten replicate measurements of the calibration blank signal
at the same wavelength (Table 1.).
3.6 Instrument Performance Check (IPC) Solution - A solution of method
analytes, used to evaluate the performance of the instrument system
200.7-5 Revi si on 4.4 May 1994
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with respect to a defined set of method criteria (Sects. 7.11 &
9.3.4).
3.7 Internal Standard - Pure analyte(s) added to a sample, extract, or
standard solution in known amount(s) and used to measure the relative
responses of other method analytes that are components of the same
sample or solution. The internal standard must be an analyte that is
not a sample component (Sect. 11.5).
3.8 Laboratory Duplicates (LD1 and LD2) - Two aliquots of the same sample
taken in the laboratory and analyzed separately with identical
procedures. Analyses of LD1 and LD2 indicates precision associated
with laboratory procedures, but not with sample collection,
preservation, or storage procedures.
3.9 Laboratory Fortified Blank (LFB) - An aliquot of LRB to which known
quantities of the method analytes are added in the laboratory. The
LFB is analyzed exactly like a sample, and its purpose is to determine
whether the methodology is in control and whether the laboratory is
capable of making accurate and precise measurements (Sects. 7.10.3 &
9.3.2).
3.10 Laboratory Fortified Sample Matrix (LFM) - An aliquot of an
environmental sample to which known quantities of the method analytes
are added in the laboratory. The LFM is analyzed exactly like a
sample, and its purpose is to determine whether the sample matrix
contributes bias to the analytical results. The background
concentrations of the analytes in the sample matrix must be determined
in a separate aliquot and the measured values in the LFM corrected for
background concentrations (Sect. 9.4).
3.11 Laboratory Reagent Blank (LRB) - An aliquot of reagent water or other
blank matrices that are treated exactly as a sample including exposure
to all glassware, equipment, solvents, reagents, and internal
standards that are used with other samples. The LRB is used to
determine if method analytes or other interferences are present in the
laboratory environment, reagents, or apparatus (Sects. 7.10.2 &
9.3.1).
3.12 Linear Dynamic Range (LDR) - The concentration range over which the
instrument response to an analyte is linear (Sect. 9.2.2).
3.13 Method Detection Limit (MDL) - The minimum concentration of an analyte
that can be identified, measured, and reported with 99% confidence
that the analyte concentration is greater than zero (Sect. 9.2.4 and
Table 4.).
3.14 Plasma Solution - A solution that is used to determine the optimum
height above the work coil for viewing the plasma (Sects. 7.15 &
10.2.3).
3.15 Quality Control Sample (QCS) - A solution of method analytes of known
concentrations which is used to fortify an aliquot of LRB or sample
matrix. The QCS is obtained from a source external to the laboratory
200.7-6 Revision 4.4 May 1994
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and different from the source of calibration standards. It is used
to check either laboratory or instrument performance (Sects. 7.12 &
«/ * £ * o y •
3.16 Solid Sample - For the purpose of this method, a sample taken from
material classified as either soil, sediment or sludge.
3.17 Spectral Interference Check (SIC) Solution - A solution of selected
method analytes of higher concentrations which is used to evaluate the
procedural routine for correcting known inters!ement spectral
interferences with respect to a defined set of method criteria (Sects.
7.13, 7.14 & 9.3.5).
3.18 Standard Addition - The addition of a known amount of analyte to the
sample in order to determine the relative response of the detector to
an analyte within the sample matrix. The relative response is then
used to assess either an operative matrix effect or the sample analvte
concentration (Sects. 9.5.1 & 11.5).
3.19 Stock Standard Solution - A concentrated solution containing one or
more method analytes prepared in the laboratory using assayed
reference materials or purchased from a reputable commercial source
(Sect. 7.8).
3.20 Total Recoverable Analyte - The concentration of analyte determined
either by "direct analysis" of an unfiltered acid preserved drinkinq
water sample with turbidity of < 1 NTU (Sect. 11.2.1), or by analysis
of the solution extract of a solid sample or an unfiltered aqueous
sample following digestion by refluxing with hot dilute mineral
acid(s) as specified in the method (Sects. 11.2 & 11.3).
3.21 Water Sample - For the purpose of this method, a sample taken from one
of the following sources: drinking, surface, ground, storm runoff,
industrial or domestic wastewater.
4.0 INTERFERENCES
4.1 Spectral interferences are caused by background emission from
continuous or recombination phenomena, stray light from the line
emission of high concentration elements, overlap of a spectral line
from another element, or unresolved overlap of molecular band spectra.
4.1.1 Background emission and stray light can usually be compensated
for by subtracting the background emission determined by
measurement(s) adjacent to the analyte wavelength peak
Spectral scans of samples or single element solutions in the
analyte regions may indicate not only when alternate
wavelengths are desirable because of severe spectral
interference, but also will show whether the most appropriate
estimate of the background emission is provided by an
interpolation from measurements on both sides of the
wavelength peak or by the measured emission on one side or the
other. The location(s) selected for the measurement of
background intensity will be determined by the complexity of
200.7-7 Revision 4.4 May 1994
-------
the spectrum adjacent to the wavelength peak. The location(s)
used for routine measurement must be free of off-line spectral
interference (interelement or molecular) or adequately
corrected to reflect the same change in background intensity
as occurs at the wavelength peak.
4.1.2 Spectral overlaps may be avoided by using an alternate
wavelength or can be compensated for by equations that correct
for interelement contributions, which involves measuring the
interfering elements. Some potential on-line spectral
interferences observed for the recommended wavelengths are
given in Table 2. When operative and uncorrected, these
interferences will produce false-positive determinations and
be reported as analyte concentrations. The interferences
listed are only those that occur between method analytes.
Only interferences of a direct overlap nature that were
observed with a single instrument having a working resolution
of 0.035 nm are listed. More extensive information on
interferant effects at various wavelengths and resolutions is
available in Boumans' Tables.8 Users may apply interelement
correction factors determined on their instruments within
tested concentration ranges to compensate (off-line or on-
line) for the effects of interfering elements.
4.1.3 When interelement corrections are applied, there is a need to
verify their accuracy by analyzing spectral interference check
solutions as described in Section 7.13. Interelement
corrections will vary for the same emission line among
instruments because of differences in resolution, as
determined by the grating plus the entrance and exit slit
widths, and by the order of dispersion. Interelement
corrections will also vary depending upon the choice of
background correction points. Selecting a background
correction point where an interfering emission line may appear
should be avoided when practical. Interelement corrections
that constitute a major portion of an emission signal may not
yield accurate data. Users should not forget that some
samples may contain uncommon elements that could contribute
spectral interferences.7'8
4.1.4 The interference effects must be evaluated for each individual
instrument whether configured as a sequential or simultaneous
instrument. For each instrument, intensities will vary not
only with optical resolution but also with operating
conditions (such as power, viewing height and argon flow
rate). When using the recommended wavelengths given in Table
1, the analyst is required to determine and document for each
wavelength the effect from the known interferences given in
Table 2, and to utilize a computer routine for their automatic
correction on all analyses. To determine the appropriate
location for off-line background correction, the user must
scan the area on either side adjacent to the wavelength and
record the apparent emission intensity from all other method
analytes. This spectral information must be documented and
200.7-8 Revision 4.4 May 1994
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kept on file. The location selected for background correction
must be either free of off-line interelement spectral
interference or a computer routine must be used for their
automatic correction on all determinations. If a wavelength
other than the recommended wavelength is used, the user must
determine and document both the on-line and off-line spectral
interference effect from all method analytes and provide for
their automatic correction on all analyses. Tests to
determine the spectral interference must be done using
analyte concentrations that will adequately describe the
interference. Normally, 100 mg/L single element solutions are
sufficient, however, for analytes such as iron that may be
found at high concentration a more appropriate test would be
to use a concentration near the upper LDR limit. See Section
10.4 for required spectral interference test criteria.
4.1.5 When interelement corrections are not used, either on-going
SIC solutions (Sect. 7.14) must be analyzed to verify the
absence of interelement spectral interference or a computer
software routine must be employed for comparing the
determinative data to limits files for notifying the analyst
when an interfering element is detected in the sample at a
concentration that will produce either an apparent false
positive concentration, > the analyte IDL, or false negative
analyte concentration, < the 99% lower control limit of the
calibration blank. When the interference accounts for 10% or
more of the analyte concentration, either an alternate
wavelength free of interference or another approved test
procedure must be used to complete the analysis. For example,
the copper peak at 213.853 nm could be mistaken for the zinc
peak at 213.856 nm in solutions with high copper and low zinc
concentrations. For this example, a spectral scan in the
213.8-nm region would not reveal the misidentification because
a single peak near the zinc location would be observed. The
possibility of this misidentification of copper for the zinc
peak at 213.856 nm can be identified by measuring the copper
at another emission line, e.g. 324.754 nm. Users, should be
aware that, depending upon the instrumental resolution,
alternate wavelengths with adequate sensitivity and freedom
from interference may not be available for all matrices. In
these circumstances the analyte must be determined using
another approved test procedure.
4.2 Physical interferences are effects associated with the sample
nebulization and transport processes. Changes in viscosity and
surface tension can cause significant inaccuracies, especially in
samples containing high dissolved solids or high acid concentrations.
If physical interferences are present, they must be reduced by such
means as a high-solids nebulizer, diluting the sample, using a
peristaltic pump, or using an appropriate internal standard element.
Another problem that can occur with high dissolved solids is sa,lt
buildup at the tip of the nebulizer, which affects aerosol flow rate
and causes instrumental drift. This problem can be controlled by a
high-solids nebulizer, wetting the argon prior to nebulization, using
200.7-9 Revision 4.4 May 1994
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a tip washer, or diluting the sample. Also, it has been reported that
better control of the argon flow rates, especially for the nebulizer,
improves instrument stability and precision; this is accomplished with
the use of mass flow controllers.
4.3 Chemical interferences include molecular-compound formation,
ionization effects, and solute-vaporization effects. Normally, these
effects are not significant with the ICP-AES technique. If observed,
they can be minimized by careful selection of operating conditions
(such as incident power and observation height), by buffering of the
sample, by matrix matching, and by standard-addition procedures.
Chemical interferences are highly dependent on matrix -type and the
specific analyte element.
4.4 Memory interferences result when analytes in a previous sample
contribute to the signals measured in a new sample. Memory effects
can result from sample deposition on the uptake tubing to the
nebulizer, and from the buildup of sample material in the plasma torch
and spray chamber. The site where these effects occur is dependent on
the element and can be minimized by flushing the system with a rinse
blank between samples (Sect. 7.10.4). The possibility of memory
interferences should be recognized within an analytical run and
suitable rinse times should be used to reduce them. The rinse times
necessary for a particular element must be estimated prior to
analysis. This may be achieved by aspirating a standard containing
elements corresponding to either their LDR or a concentration ten
times those usually encountered. The aspiration time should be the
same as a normal sample analysis period, followed by analysis of the
rinse blank at designated intervals. The length of time required to
reduce analyte signals to within a factor of two of the method
detection limit, should be noted. Until the required rinse time is
established, this method requires a rinse period of at least 60 sec
between samples and standards. If a memory interference is suspected,
the sample must be re-analyzed after a long rinse period.
5.0 SAFETY
5.1 The toxicity or carcinogenicity of each reagent used in this method
have not been fully established. Each chemical should be regarded as
a potential health hazard and exposure to these compounds should be as
low as reasonably achievable. Each laboratory is responsible for
maintaining a current awareness file of OSHA regulations regarding the
safe handling of the chemicals specified in this method.9" A
reference file of material data handling sheets should also be made
available to all personnel involved in the chemical analysis.
Specifically, concentrated nitric and hydrochloric acids present
various hazards and are moderately toxic and extremely irritating to
skin and mucus membranes. Use these reagents in a fume hood whenever
•possible and if eye or skin contact occurs, flush with large volumes
of water. Always wear safety glasses or a shield for eye protection,
protective clothing and observe proper mixing when working with these
reagents.
200.7-10 Revi si on 4.4 May 1994
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5.2 The acidification of samples containing reactive materials may result
in the release of toxic gases, such as cyanides or sulfides.
Acidification of samples should be done in a fume hood.
5.3 All personnel handling environmental samples known to contain or to
have been in contact with human waste should be immunized against
known disease causative agents.
5.4 The inductively coupled plasma should only be viewed with proper eye
protection from the ultraviolet emissions.
5.5 It is the responsibility of the user of this method to comply with
relevant disposal and waste regulations. For guidance see Sections
14.0 and 15.0.
6.0 EQUIPMENT AND SUPPLIES
6.1 Inductively coupled plasma emission spectrometer:
6.1.1 Computer-controlled emission spectrometer with background-
correction capability. The spectrometer must be capable of
meeting and complying with the requirements described and
referenced in Section 2.2.
6.1.2 Radio-frequency generator compliant with FCC regulations.
6.1.3 Argon gas supply - High purity grade (99.99%). When analyses
are conducted frequently, liquid argon is more economical and
requires less frequent replacement of tanks than compressed
argon in conventional cylinders.
6.1.4 A variable speed peristaltic pump is required to deliver both
standard and sample solutions to the nebulizer.
6.1.5 (optional) Mass flow controllers to regulate the argon flow
rates, especially the aerosol transport gas, are highly
recommended. Their use will provide more exacting control of
reproducible plasma conditions.
6.2 Analytical balance, with capability to measure to 0.1 mg, for use in
weighing solids, for preparing standards, and for determining
dissolved solids in digests or extracts.
6.3 A temperature adjustable hot plate capable of maintaining a
temperature of 95°C.
6.4 (optional) A temperature adjustable block digester capable of
maintaining a temperature of 95°C and equipped with 250-mL constricted
digestion tubes.
6.5 (optional) A steel cabinet centrifuge with guard bowl, electric timer
and brake.
200.7-11 Revi si on 4.4 May 1994
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6.6 A gravity convection drying oven with thermostatic control capable of
maintaining 180°C ± 5°C.
6.7 (optional) An air displacement pipetter capable of delivering volumes
ranging from 0.1 to 2500 /iL with an assortment of high quality
disposable pipet tips.
6.8 Mortar and pestle, ceramic or nonmetallic material.
6.9 Polypropylene sieve, 5-mesh (4 mm opening).
6.10 Labware - For determination of trace levels of elements, contamination
and loss are of prime consideration. Potential contamination sources
include improperly cleaned laboratory apparatus and general
contamination within the laboratory environment from dust, etc. A
clean laboratory work area designated for trace element sample
handling must be used. Sample containers can introduce positive and
negative errors in the determination of trace elements by (1)
contributing contaminants through surface desorption or leaching, (2)
depleting element concentrations through adsorption processes. All
reusable labware (glass, quartz, polyethylene, PTFE, FEP, etc.) should
be sufficiently clean for the task objectives. Several procedures
found to provide clean labware include washing with a detergent
solution, rinsing with tap water, soaking for 4 h or more in 20% (v/v)
nitric acid or a mixture of HN03 and HC1 (1+2+9), rinsing with reagent
water and storing clean.2' Chromic acid cleaning solutions must be
avoided because chromium is an analyte.
6.10.1 Glassware - Volumetric flasks, graduated cylinders, funnels
and centrifuge tubes (glass and/or metal-free plastic).
6.10.2 Assorted calibrated pipettes.
6.10.3 Conical Phillips beakers (Corning 1080-250 or equivalent),
250-mL with 50-mm watch glasses.
6.10.4 Griffin beakers, 250-mL with 75-mm watch glasses and
(optional) 75-mm ribbed watch glasses.
6.10.5 (optional) PTFE and/or quartz Griffin beakers, 250-mL with
PTFE covers.
6.10.6 Evaporating dishes or high-form crucibles, porcelain, 100 mL
capacity.
6.10.7 Narrow-mouth storage bottles, FEP (fluorinated ethylene
propylene) with screw closure, 125-mL to 1-L capacities.
6.10.8 One-piece stem FEP wash bottle with screw closure, 125-mL
capacity.
200.7-12 Revision4.4 May 1994
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7.0 REAGENTS AND STANDARDS
7.1 Reagents may contain elemental impurities which might affect
analytical data. Only high-purity reagents that conform to the
American Chemical Society specifications 3 should be used whenever
possible. If the purity of a reagent is in question, analyze for
contamination. All acids used for this method must be of ultra high-
purity grade or equivalent. Suitable acids are available from a
number of manufacturers. Redistilled acids prepared by sub-boiling
distillation are acceptable.
7.2 Hydrochloric acid, concentrated (sp.gr. 1.19) - HC1.
7.2.1 Hydrochloric acid (1+1) - Add 500 ml concentrated HC1 to"400
mL reagent water and dilute to 1 L.
7.2.2 Hydrochloric acid (1+4) - Add 200 ml concentrated HC1 to 400
ml reagent water and dilute to 1 L.
7.2.3 Hydrochloric acid (1+20) - Add 10 ml concentrated HC1 to 200
ml reagent water.
7.3 Nitric acid, concentrated (sp.gr. 1.41) - HN03.
7.3.1 Nitric acid (1+1) - Add 500 ml concentrated HN03 to 400 ml
reagent water and dilute to 1 L.
7.3.2 Nitric acid (1+2) - Add 100 ml concentrated HN03 to 200 ml
reagent water.
7.3.3 Nitric acid (1+5) - Add 50 ml concentrated HN03 to 250 ml
reagent water.
7.3.4 Nitric acid (1+9) - Add 10 ml concentrated HN03 to 90 ml
reagent water.
7.4 Reagent water. All references to water in this method refer to ASTM
Type I grade water.
7.5 Ammonium hydroxide, concentrated (sp. gr. 0.902).
7.6 Tartaric acid, ACS reagent grade.
7.7 Hydrogen peroxide, 50%, stabilized certified reagent grade.
7.8 Standard Stock Solutions - Stock standards may be purchased or
prepared from ultra-high purity grade chemicals (99.99 to 99.999%
pure). All compounds must be dried for 1 h at 105°C, unless
otherwise specified. It is recommended that stock solutions be stored
in FEP bottles. Replace stock standards when succeeding dilutions for
preparation of calibration standards cannot be verified.
CAUTION: Many of these chemicals are extremely toxic if inhaled or
swallowed (Sect. 5.1). Wash hands thoroughly after handling.
200.7-13 Revision4.4 May 1994
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Typical stock solution preparation procedures follow for 1-L
quantities, but for the purpose of pollution prevention, the analyst
is encouraged to prepare smaller quantities when possible.
Concentrations are calculated based upon the weight of the pure
element or upon the weight of the compound multiplied by the fraction
of the analyte in the compound.
From pure element,
weight (mg)
Concentration =
volume (L)
From pure compound,
weight (mg) x gravimetric factor
Concentration =
volume (L)
where:
gravimetric factor = the weight fraction of the analyte in the
compound.
7.8.1 Aluminum solution, stock, 1 ml = 1000 /zg Al: Dissolve 1.000 g
of aluminum metal, weighed accurately to at least four
significant figures, in an acid mixture of 4.0 ml of (1+1) HC1
and 1.0 ml of concentrated HN03 in a beaker. Warm beaker
slowly to effect solution. When dissolution is complete,
transfer solution quantitatively to a 1-L flask, add an
additional 10.0 ml of (1+1) HC1 and dilute to volume with
reagent water.
7.8.2 Antimony solution, stock, 1 ml = 1000 fig Sb: Dissolve 1.000
g of antimony powder, weighed accurately to at least four
significant figures, in 20.0 ml (1+1) HN03 and 10.0 ml
concentrated HC1. Add 100 ml reagent water and 1.50 g
tartaric acid. Warm solution slightly to effect complete
dissolution. Cool solution and add reagent water to volume in
a 1-L volumetric flask.
7.8.3 Arsenic solution, stock, 1 mL = 1000 /KJ As: Dissolve 1.320 g
of As203 (As fraction = 0.7574), weighed accurately to at
least four significant figures, in 100 mL of reagent water
containing 10.0 mL concentrated NH,OH. Warm the solution
gently to effect dissolution. Acidify the solution with 20.0
mL concentrated HN03 and dilute to volume in a 1-L volumetric
flask with reagent water.
7.8.4 Barium solution, stock, 1 mL = 1000 /jg Ba: Dissolve 1.437 g
BaC03 (Ba fraction = 0.6960), weighed accurately to at least
200.7-14 Revision 4.4 May 1994
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four significant figures, in 150 ml (1+2) HN03 with heating
and stirring to degas and dissolve compound. Let solution
cool and dilute with reagent water in 1-L volumetric flask.
7.8.5 Beryllium solution, stock, 1 ml = 1000 jug Be: DO NOT DRY.
Dissolve 19.66 g BeS04»4H20 (Be fraction = 0.0509), weighed
accurately to at least four significant figures, in reagent
water, add 10.0 ml concentrated HN03, and dilute to volume in
a 1-L volumetric flask with reagent water.
7.8.6 Boron solution, stock, 1 ml = 1000 #g B: DO NOT DRY. Dissolve
5.716 g anhydrous H3BO, (B fraction = 0.1749), weighed
accurately to at least four significant figures, in reagent
water and dilute in a 1-L volumetric flask with reagent water.
Transfer immediately after mixing to a clean FEP bottle to
minimize any leaching of boron from the glass volumetric
container. Use of a nonglass volumetric flask is recommended
to avoid boron contamination from glassware.
7.8.7 Cadmium solution, stock, 1 mL = 1000 /jg Cd: Dissolve 1.000 g
Cd metal, acid cleaned with (1+9) HN03, weighed accurately to
at least four significant figures, in 50 mL (1+1) HN03 with
heating to effect dissolution. Let solution cool and dilute
with reagent water in a 1-L volumetric flask.
7.8.8 Calcium solution, stock, 1 mL = 1000 /ig Ca: Suspend 2.498 g
CaCO, (Ca fraction = 0.4005), dried at 180°C for 1 h before
weighing, weighed accurately to at least four significant
figures, in reagent water and dissolve cautiously with a
minimum amount of (1+1) HN03. Add 10.0 mL concentrated HN03
and dilute to volume in a 1-L volumetric flask with reagent
water.
7.8.9 Cerium solution, stock, 1 mL = 1000 #g Ce: Slurry 1.228 g Ce02
(Ce fraction = 0.8141), weighed accurately to at least four
significant figures, in 100 mL concentrated HN03 and evaporate
to dryness. Slurry the residue in 20 mL H20, add 50 mL
concentrated HN03, with heat and stirring add 60 mL 50% H202
dropwise in 1 mL increments allowing periods of stirring
between the 1 mL additions. Boil off excess H202 before
diluting to volume in a 1-L volumetric flask with reagent
water.
7.8.10 Chromium solution, stock, 1 mL = 1000 fig Cr: Dissolve 1.923
g Cr03 (Cr fraction = 0.5200), weighed accurately to at least
four significant figures, in 120 mL (1+5) HN03. When solution
is complete, dilute to volume in a 1-L volumetric flask with
reagent water.
7.8.11 Cobalt solution, stock, 1 mL = 1000 fig Co: Dissolve 1.000 g
Co metal, acid cleaned with (1+9) HN03, weighed accurately to
at least four significant figures, in 50.0 mL (1+1) HN03. Let
solution cool and dilute to volume in a 1-L volumetric flask
with reagent water.
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7.8.12 Copper solution, stock, 1 ml = 1000 p,g Cu: Dissolve 1.000 g Cu
metal, acid cleaned with (1+9) HNO,, weighed accurately to at
least four significant figures, in 50.0 ml (1+1) HN03 with
heating to effect dissolution. Let solution cool and dilute
in a 1-L volumetric flask with reagent water.
7.8.13 Iron solution, stock, 1 ml = 1000 /jg Fe: Dissolve 1.000 g Fe
metal, acid cleaned with (1+1) HC1, weighed accurately to four
significant figures, in 100 ml (1+1) HC1 with heating to
effect dissolution. Let solution cool and dilute with reagent
water in a 1-L volumetric flask.
7.8.14 Lead solution, stock, 1 mL = 1000 ng Pb: Dissolve 1.599 g
Pb(N03)p (Pb fraction = 0.6256), weighed accurately to at
least four significant figures, in a minimum amount of (1+1)
HN03. Add 20.0 mL (1+1) HN03 and dilute to volume in a 1-L
volumetric flask with reagent water.
7.8.15 Lithium solution, stock, 1 mL = 1000 //,g Li: Dissolve 5.324 g
Li2C03 (Li fraction = 0.1878), weighed accurately to at least
four significant figures, in a minimum amount of (1+1) HC1 and
dilute to volume in a 1-L volumetric flask with reagent water.
7.8.16 Magnesium solution, stock, 1 mL = 1000 /zg Mg: Dissolve 1.000
g cleanly polished Mg ribbon, accurately weighed to at least
four significant figures, in slowly added 5.0 mL (1+1) HC1
(CAUTION: reaction is vigorous). Add 20.0 mL (1+1) HN03 and
dilute to volume in a 1-L volumetric flask with reagent water.
7.8.17 Manganese solution, stock, 1 mL = 1000 /ug Mn: Dissolve 1.000
g of manganese metal, weighed accurately to at least four
significant figures, in 50 mL (1+1) HN03 and dilute to volume
in a 1-L volumetric flask with reagent, water.
7.8.18 Mercury solution, stock, 1 mL = 1000 /ig Hg: DO NOT DRY.
CAUTION: highly toxic element. Dissolve 1.354 g HgCl2 (Hg
fraction = 0.7388) in reagent water. Add 50.0 mL concentrated
HN03 and dilute to volume in 1-L volumetric flask with reagent
water.
7.8.19 Molybdenum solution, stock, 1 mL = 1000 ng Mo: Dissolve 1.500
g Mo03 (Mo fraction = 0.6666), weighed accurately to at least
four significant figures, in a mixture of 100 mL reagent water
and 10.0 mL concentrated NH4OH, heating to effect dissolution.
Let solution cool and dilute with reagent water in a 1-L
volumetric flask.
7.8.20 Nickel solution, stock, 1 mL = 1000 ng Ni: Dissolve 1.000 g
of nickel metal, weighed accurately to at least four
significant figures, in 20.0 mL hot concentrated HN03, cool,
and dilute to volume in a 1-L volumetric flask with reagent
water.
200.7-16 Revision4.4 May 1994
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7.8.21 Phosphorus solution, stock, 1 ml = 1000 /jg P: Dissolve 3.745
g NH4H;,P04 (P fraction = 0.2696), weighed accurately to at
least four significant figures, in 200 ml reagent water and
dilute to volume in a 1-L volumetric flask with reagent water.
7.8.22 Potassium solution, stock, 1 ml = 1000 /jg K: Dissolve 1.907 g
KC1 (K fraction = 0.5244) dried at 110°C, weighed accurately
to at least four significant figures, in reagent water, add 20
mL (1+1) HC1 and dilute to volume in a 1-L volumetric flask
with reagent water.
7.8.23 Selenium solution, stock, 1 ml = 1000 fig Se: Dissolve 1.405 g
Se02 (Se fraction = 0.7116)s weighed accurately to at least
four significant figures, in 200 ml reagent water and dilute
to volume in a 1-L volumetric flask with reagent water.
7.8.24 Silica solution, stock, 1 ml = 1000 #g Si02: DO NOT DRY.
Dissolve 2.964 g (NH4)2SiF6, weighed accurately to at least
four significant figures, in 200 ml (1+20) HC1 with heating at
85°C to effect dissolution. Let solution cool and dilute to
volume in a 1-L volumetric flask with reagent water.
7.8.25 Silver solution, stock, 1 mL = 1000 /tg Ag: Dissolve 1.000 g
Ag metal, weighed accurately to at least four significant
figures, in 80 mL (1+1) HN03 with heating to effect
dissolution. Let solution cool and dilute with reagent water
in a 1-L volumetric flask. Store solution in amber bottle or
wrap bottle completely with aluminum foil to protect solution
from light.
7.8.26 Sodium solution, stock, 1 mL = 1000 ng Na: Dissolve 2.542 g
NaCl (Na fraction = 0.3934), weighed accurately to at least
four significant figures, in reagent water. Add 10.0 mL
concentrated HN03 and dilute to volume in a 1-L volumetric
flask with reagent water.
7.8.27 Strontium solution, stock, 1 mL = 1000 jug Sr: Dissolve 1.685
g SrC03 (Sr fraction = 0.5935), weighed accurately to at least
four significant figures, in 200 mL reagent water with
dropwise addition of 100 mL (1+1) HC1. Dilute to volume in a
1-L volumetric flask with reagent water.
7.8.28 Thallium solution, stock, 1 mL = 1000 /jg Tl: Dissolve 1.303 g
T1N03 (Tl fraction = 0.7672), weighed accurately to at least
four significant figures, in reagent water. Add 10.0 mL
concentrated HN03 and dilute to volume in a 1-L volumetric
flask with reagent water.
7.8.29 Tin solution, stock, 1 mL = 1000 /tg Sn: Dissolve 1.000 g Sn
shot, weighed accurately to at least four significant figures,
in an acid mixture of 10.0 mL concentrated HC1 and 2.0 mL
(1+1) HN03 with heating to effect dissolution. Let solution
cool, add 200 mL concentrated HC1, and dilute to volume in a
1-L volumetric flask with reagent water.
200.7-17 Revision 4.4 May 1994
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7.8.30 Titanium solution, stock, 1 ml = 1000 /jg Ti: DO NOT DRY.
Dissolve 6.138 g (NH4)2TiO(C20,)2«H20 (Ti fraction = 0.1629),
weighed accurately to at least four significant figures, in
100 mL reagent water. Dilute to volume in a 1-L volumetric
flask with reagent water.
7.8.31 Vanadium solution, stock, 1 ml = 1000 /wj V: Dissolve 1.000 g
V metal, acid cleaned with (1+9) HN03, weighed accurately to
at least four significant figures, in 50 ml (1+1) HNO, with
heating to effect dissolution. Let solution cool and dilute
with reagent water to volume in a 1-L volumetric flask.
7.8.32 Yttrium solution, stock 1 mL = 1000 ng Y: Dissolve 1.270 g
Y203 (Y fraction = 0.7875), weighed accurately to at least
four significant figures, in 50 mL (1+1) HN03, heating to
effect dissolution. Cool and dilute to volume in a 1-L
volumetric flask with reagent water.
7.8.33 Zinc solution, stock, 1 mL = 1000 /fg Zn: Dissolve 1.000 g Zn
metal, acid cleaned with (1+9) HN03, weighed accurately to at
least four significant figures, in 50 mL (1+1) HN03 with
heating to effect dissolution. Let solution cool and dilute
with reagent water to volume in a 1-L volumetric flask.
7.9 Mixed Calibration Standard Solutions - For the analysis of total
recoverable digested samples prepare mixed calibration standard
solutions (see Table 3) by combining appropriate volumes of the stock
solutions in 500-mL volumetric flasks containing 20 mL (1+1) HN03 and
20 mL (1+1) HC1 and dilute to volume with reagent water. Prior to
preparing the mixed standards, each stock solution should be analyzed
separately to determine possible spectral interferences or the
presence of impurities. Care should be taken when preparing the mixed
standards to ensure that the elements are compatible and stable
together. To minimize the opportunity for contamination by the
containers, it is recommended to transfer the mixed-standard solutions
to acid-cleaned, never-used FEP fluorocarbon (FEP) bottles for
storage. Fresh mixed standards should be prepared, as needed, with
the realization that concentrations can change on aging. Calibration
standards not prepared from primary standards must be initially
verified using a certified reference solution. For the recommended
wavelengths listed in Table 1 some typical calibration standard
combinations are given in Table 3.
NOTE: If the addition of silver to the recommended mixed-acid
calibration standard results in an initial precipitation, add
15 mL of reagent water and warm the flask until the solution
clears. For this acid combination, the silver concentration
should be limited to 0.5 mg/L.
7.10 Blanks - Four types of blanks are required for the analysis. The
calibration blank is used in establishing the analytical curve, the
laboratory reagent blank is used to assess possible contamination from
the sample preparation procedure, the laboratory fortified blank is
used to assess routine laboratory performance and a rinse blank is
200.7-18 Revision 4.4 May 1994
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used to flush the instrument uptake system and nebulizer between
standards, check solutions, and samples to reduce memory
interferences.
7.10.1 The calibration blank for aqueous samples and extracts is
prepared by acidifying reagent water to the same
concentrations of the acids as used for the standards. The
calibration blank should be stored in a FEP bottle.
7.10.2 The laboratory reagent blank (LRB) must contain all the
reagents in the same volumes as used in the processing of the
samples. The LRB must be carried through the same entire
preparation scheme as the samples including sample digestion,
when applicable.
7.10.3 The laboratory fortified blank (LFB) is prepared by fortifying
an aliquot of the laboratory reagent blank with all analytes
to a suitable concentration using the following recommended
criteria: Ag < 0.1 mg/L, > K 5.0 mg/L and all other analytes
0.2 mg/L or a concentration approximately 100 times their
respective MDL, whichever is greater. The LFB must be carried
through the same entire preparation scheme as the samples
including sample digestion, when applicable.
7.10.4 The rinse blank is prepared by acidifying reagent water to the
same concentrations of acids as used in the calibration blank
and stored in a convenient manner.
7.11 Instrument Performance Check (IPC) Solution - The IPC solution is used
to periodically verify instrument performance during analysis. It
should be prepared in the same acid mixture as the calibration
standards by combining method analytes at appropriate concentrations.
Silver must be limited to < 0.5 mg/L; while potassium and phosphorus
because of higher MDLs and silica because of potential contamination
should be at concentrations of 10 mg/L. For other analytes a
concentration of 2 mg/L is recommended. The IPC solution should be
prepared from the same standard stock solutions used to prepare the
calibration standards and stored in an FEP bottle. Agency programs
may specify or request that additional instrument performance check
solutions be prepared at specified concentrations in order to meet
particular program needs.
7.12 Quality Control Sample (QCS) - Analysis of a QCS is required for
initial and periodic verification of calibration standards or stock
standard solutions in order to verify instrument performance. The QCS
must be obtained from an outside source different from the standard
stock solutions and prepared in the same acid mixture as the
calibration standards. The concentration of the analytes in the QCS
solution should be > 1 mg/L, except silver, which must be limited to
a concentration of 0.5 mg/L for solution stability. The QCS solution
should be stored in a FEP bottle and analyzed as needed to meet data-
quality needs. A fresh solution should be prepared quarterly or more
frequently as needed.
200.7-19 Revi si on 4.4 May 1994
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7.13 Spectral Interference Check (SIC) Solutions - When interelement
corrections are applied, SIC solutions are needed containing
concentrations of the interfering elements at levels that will provide
an adequate test of the correction factors.
7.13.1 SIC solutions containing (a) 300 mg/L Fe; (b) 200 mg/L AL; (c)
50 mg/L Ba; (d) 50 mg/L Be; (e) 50 mg/L Cd; (f) 50 mg/L Ce;
(g) 50 mg/L Co; (h) 50 mg/L Cr; (i) 50 mg/L Cu; (j) 50 mg/L
Mn; (k) 50 mg/L Mo; (1) 50 mg/L Ni; (m) 50 mg/L Sn; (n) 50
mg/L Si02; (o) 50 mg/L Ti; (p) 50 mg/L Tl and (q) 50 mg/L V
should be prepared in the same acid mixture as the calibration
standards and stored in FEP bottles. These solutions can be
used to periodically verify a partial list of the on-line (and
possible off-line) interelement spectral correction factors
for the recommended wavelengths given in Table 1. Other
solutions could achieve the same objective as well.
(Multielement SIC solutions3 may be prepared and substituted
for the single element solutions provided an analyte is not
subject to interference from more than one interferant in the
solution.)
NOTE: If wavelengths other than those recommended in Table 1
are used, other solutions different from those above (a
thru q) may be required.
7.13.2 For interferences from iron and aluminum, only those
correction factors (positive or negative) when multiplied by
100 to calculate apparent analyte concentrations that exceed
the determined analyte IDL or fall below the lower 3-sigma
control limit of the calibration blank need be tested on a
daily basis.
7.13.3 For the other interfering elements, only those correction
factors (positive or negative) when multiplied by 10 to
calculate apparent analyte concentrations that exceed the
determined analyte IDL or fall below the lower 3-sigma control
limit of the calibration blank need be tested on a daily
basis.
7.13.4 If the correction routine is operating properly, the
determined apparent analyte(s) concentration from analysis of
each interference solution (a thru q) should fall within a
specific concentration range bracketing the calibration blank.
This concentration range is calculated by multiplying the
concentration of the interfering element by the value of the
correction factor being tested and dividing by 10. If after
subtraction of the calibration blank the apparent analyte
concentration is outside (above or below) this range, a change
in the correction factor of more than 10% should be suspected.
The cause of the change should be determined and corrected and
the correction factor should be updated.
NOTE: The SIC solution should be analyzed more than once to
confirm a change has occurred with adequate rinse time
200.7-20 Revi si on 4.4 May 1994
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between solutions and before subsequent analysis of the
calibration blank.
7.13.5 If the correction factors tested on a daily basis are found to
be within the 10% criteria for 5 consecutive days the
required verification frequency of those factors in compliance
may be extended to a weekly basis. Also, if the nature of the
samples analyzed is such (e.g., finished drinking water) that
they do not contain concentrations of the interfering elements
at the 10-mg/L level, daily verification is not required-
however, all interelement spectral correction factors must be
verified annually and updated, if necessary.
7.13.6 If the instrument does not display negative concentration
values, fortify the SIC solutions with the elements of
interest at 1 mg/L and test for analyte recoveries that are
below 95%. In the absence of measurable analyte over-
correction could go undetected because a negative value could
be reported as zero.
7.14 For instruments without interelement correction capability or when
interelement corrections are not used, SIC solutions (containing
similar concentrations of the major components in the samples eg
> 10 mg/L) can serve to verify the absence of effects at 'the
wavelengths selected. These data must be kept on file with the sample
analysis data. If the SIC solution confirms an operative interference
that is ^ 10% of the analyte concentration, the analyte must be
determined using a wavelength and background correction location free
of the interference or by another approved test procedure Users are
advised that high salt concentrations can cause analyte signal
suppressions and confuse interference tests.
7.15 Plasma Solution - The plasma solution is used for determining the
optimum viewing height of the plasma above the work coil prior to
using the method (Sect. 10.2). The solution is prepared by adding a
5-mL aliquot from each of the stock standard solutions of arsenic
lead, selenium, and thallium to a mixture of 20 ml (1+1) nitric acid
and 20 ml (1+1) hydrochloric acid and diluting to 500 ml with reagent
water. Store in a FEP bottle.
8-° SAMPLE COLLECTION. PRESERVATION. AND STORAGE
8.1 Prior to the collection of an aqueous sample, consideration should be
given to the type of data required, (i.e., dissolved or total
recoverable), so that appropriate preservation and pretreatment steps
can be taken. The pH of all aqueous samples must be tested
immediately prior to aliquoting for processing or "direct analysis" to
ensure the sample has been properly preserved. If properly acid
preserved, the sample can be held up to 6 months before analysis.
8.2 For the determination of the dissolved elements, the sample must be
filtered through a 0.45-/im pore diameter membrane filter at the time
of collection or as soon thereafter as practically possible. (Glass
or plastic filtering apparatus are recommended to avoid possible
200.7-21 Revision 4.4 May 1994
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contamination. Only plastic apparatus should be used when the
determinations of boron and silica are critical.) Use a portion of
the filtered sample to rinse the filter flask, discard this portion
and collect the required volume of filtrate. Acidify the filtrate
with (1+1) nitric acid immediately following filtration to pH < 2.
8.3 For the determination of total recoverable elements in aqueous
samples, samples are not filtered, but acidified with (1+1) nitric
acid to pH < 2 (normally, 3 ml of (1+1) acid per liter of sample is
sufficient for most ambient and drinking water samples). Preservation
may be done at the time of collection, however, to avoid the hazards
of strong acids in the field, transport restrictions, and possible
contamination it is recommended that the samples be returned to the
laboratory within two weeks of collection and acid preserved upon
receipt in the laboratory. Following acidification, the sample should
be mixed, held for sixteen hours, and then verified to be pH < 2 just
prior withdrawing an aliquot for processing or "direct analysis". If
for some reason such as high alkalinity the sample pH is verified to
be > 2, more acid must be added and the sample held for sixteen hours
until verified to be pH < 2. See Section 8.1:
NOTE: When the nature of the sample is either unknown or is known to
be hazardous, acidification should be done in a fume hood.
See Section 5.2.
8.4 Solid samples require no preservation prior to analysis other than
storage at 4°C. There is no established holding time limitation for
solid samples.
8.5 For aqueous samples, a field blank should be prepared and analyzed as
required by the data user. Use the same container and acid as used in
sample collection.
9.0 QUALITY CONTROL
9.1 Each laboratory using this method is required to operate a formal
quality control (QC) program. The minimum requirements of this program
consist of an initial demonstration of laboratory capability, and the
periodic analysis of laboratory reagent blanks, fortified blanks and
other laboratory solutions as a continuing check on performance. The
laboratory is required to maintain performance records that define the
quality of the data thus generated.
9.2 Initial Demonstration of Performance (mandatory).
9.2.1 The initial demonstration of performance is used to
characterize instrument performance (determination of linear
dynamic ranges and analysis of quality control samples) and
laboratory performance (determination of method detection
limits) prior to analyses conducted by this method.
9.2.2 Linear dynamic range (LDR) - The upper limit of the LDR must
be established for each wavelength utilized. It must be
200.7-22 Revision 4.4 May 1994
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determined from a linear calibration prepared in the normal
manner using the established analytical operating procedure
for the instrument. The LDR should be determined by analyzing
succeedingly higher standard concentrations of the analyte
until the observed analyte concentration is no more than 10%
below the stated concentration of the standard. Determined
LDRs must be documented and kept on file. The LDR which may
be used for the analysis of samples should be judged by the
analyst from the resulting data. Determined sample analyte
concentrations that are greater than 90% of the determined
upper LDR limit must be diluted and reanalyzed. The LDRs
should be verified annually or whenever, in the judgement of
the analyst, a change in analytical performance caused by
either a change in instrument hardware or operating conditions
would dictate they be redetermined.
9.2.3 Quality control sample (QCS) - When beginning the use of this
method, on a quarterly basis, after the preparation of stock or
calibration standard solutions or as required to meet data-
quality needs, verify the calibration standards and acceptable
instrument performance with the preparation and analyses of a
QCS (Sect. 7.12). To verify the calibration standards the
determined mean concentrations from 3 analyses of the QCS must
be within ± 5% of the stated values. If the calibration
standard cannot be verified, performance of the determinative
step of the method is unacceptable. The source of the problem
must be identified and corrected before either proceeding on
with the initial determination of method detection limits or
continuing with on-going analyses.
9.2.4 Method detection limit (MDL) - MDLs must be established for
all wavelengths utilized, using reagent water (blank) fortified
at a concentration of two to three times the estimated
instrument detection limit.15 To determine MDL values, take
seven replicate aliquots of the fortified reagent water and
process through the entire analytical method. Perform all
calculations defined in the method and report the concentration
values in the appropriate units. Calculate the MDL as follows:
MDL- (t) x (S)
where: t = students' t value for a 99% confidence level and
a standard deviation estimate with n-1 degrees of
freedom [t = 3.14 for seven replicates].
S = standard deviation of the replicate analyses.
Note: If additional confirmation is desired, reanalyze the
seven replicate aliquots on two more nonconsecutive
days and again calculate the MDL values for each day.
An average of the three MDL values for each analyte
may provide for a more appropriate MDL estimate. If
the relative standard deviation (RSD) from the analyses
200.7-23 Revision 4.4 May 1994
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of the seven aliquots is < 10%, the concentration used
to determine the analyte MDL may have been inapprop-
riately high for the determination. If so, this could
result in the calculation of an unrealistically low
MDL. Concurrently, determination of MDL in reagent
water represents a best case situation and does not
reflect possible matrix effects of real world samples.
However, successful analyses of LFMs (Sect. 9.4) and
the analyte addition test described in Section 9.5.1
can give confidence to the MDL value determined in
reagent water. Typical single laboratory MDL values
using this method are given in Table 4.
The MDLs must be sufficient to detect analytes at the required
levels according to compliance monitoring regulation (Sect.
1.2). MDLs should be determined annually, when a new operator
begins work or whenever, in the judgement of the analyst, a
change in analytical performance caused by either a change in
instrument hardware or operating conditions would dictate they
be redetermined.
9.3 Assessing Laboratory Performance (mandatory)
9.3.1 Laboratory reagent blank (LRB) - The laboratory must analyze at
least one LRB (Sect. 7.10.2) with each batch of 20 or fewer
samples of the same matrix. LRB data are used to assess
contamination from the laboratory environment. LRB values that
exceed the MDL indicate laboratory or reagent contamination
should be suspected. When LRB values constitute 10% or more of
the analyte level determined for a sample or is 2.2 times the
analyte MDL whichever is greater, fresh aliquots of the samples
must be prepared and analyzed again for the affected analytes
after the source of contamination has been corrected and
acceptable LRB values have been obtained.
9.3.2 Laboratory fortified blank (LFB) - The laboratory must analyze
at least one LFB (Sect. 7.10.3) with each batch of samples.
Calculate accuracy as percent recovery using the following
equation:
LFB - LRB
R = X 100
where: R = percent recovery.
LFB = laboratory fortified blank.
LRB = laboratory reagent blank.
s = concentration equivalent of analyte
added to fortify the LBR solution.
If the recovery of any analyte falls outside the required
control limits of 85-115%, that analyte is judged out of
200.7-24 Revision 4.4 May 1994
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control, and the source of the problem should be identified and
resolved before continuing analyses.
9.3.3 The laboratory must use LFB analyses data to assess laboratory
performance against the required control limits of 85-115%
(Sect.9.3.2). When sufficient internal performance data become
available (usually a minimum of twenty to thirty analyses),
optional control limits can be developed from the mean percent
recovery (x) and the standard deviation (S) of the mean percent
recovery. These data can be used to establish the upper and
lower control limits as follows:
UPPER CONTROL LIMIT = x + 3S
LOWER CONTROL LIMIT = x - 3S
The optional control limits must be equal to or better than the
required control limits of 85-115%. After each five to ten new
recovery measurements, new control limits can be calculated
using only the most recent twenty to thirty data points. Also,
the standard deviation (S) data should be used to establish an
on-going precision statement for the level of concentrations
included in the LFB. These data must be kept on file and be
available for review.
9.3.4 Instrument performance check (IPC) solution - For all
determinations the laboratory must analyze the IPC solution
(Sect. 7.11) and a calibration blank immediately following
daily calibration, after every tenth sample (or more
frequently, if required) and at the end of the sample run.
Analysis of the calibration blank should always be < the
analyte IDL, but > the lower 3-sigma control limit of the
calibration blank. Analysis of the IPC solution immediately
following calibration must verify that the instrument is within
± 5% of calibration with a relative standard deviation < 3%
from replicate integrations > 4. Subsequent analyses of the
IPC solution must be within ± 10% of calibration. If the
calibration cannot be verified within the specified limits,
reanalyze either or both the IPC solution and the calibration
blank. If the second analysis of the IPC solution or the
calibration blank confirm calibration to be outside the limits,
sample analysis must be discontinued, the cause determined,
corrected and/or the instrument recalibrated. All samples
following the last acceptable IPC solution must be reanalyzed.
The analysis data of the calibration blank and IPC solution
must be kept on file with the sample analyses data.
9.3.5 Spectral interference check (SIC) solution - For all
determinations the laboratory must periodically verify the
interelement spectral interference correction routine by
analyzing SIC solutions. The preparation and required periodic
analysis of SIC solutions and test criteria for verifying the
interelement interference correction routine are given in
Section 7.13. Special cases where on-going verification is
required are described in Section 7.14.
200.7-25 Revision 4.4 May 1994
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9.4 Assessing Analyte Recovery and Data Quality
9.4.1 Sample homogeneity and the chemical nature of the sample matrix
can affect analyte recovery and the quality of the data.
Taking separate aliquots from the sample for replicate and
fortified analyses can in some cases assess the effect. Unless
otherwise specified by the data user, laboratory or program,
the following laboratory fortified matrix (LFM) procedure (Sect
9.4.2) is required. Also, other tests such as the analyte
addition test (Sect. 9.5.1) and sample dilution test (Sect.
9.5.2) can indicate if matrix effects are operative.
9.4.2 The laboratory must add a known amount of each analyte to a
minimum of 10% of the routine samples. In each case the LFM
aliquot must be a duplicate of the aliquot used for sample
analysis and for total recoverable determinations added prior
to sample preparation. For water samples, the added analyte
concentration must be the same as that used in the laboratory
fortified blank (Sect. 7.10.3). For solid samples, however,
the concentration added should be expressed as mg/kg and is
calculated for a one gram aliquot by multiplying the added
analyte concentration (mg/L) in solution by the conversion
factor 100 (mg/L x 0.1L/0.001kg = 100, Sect. 12.5). (For notes
on Ag, Ba, and Sn see Sects. 1.7 & 1.8.) Over time, samples
from all routine sample sources should be fortified.
NOTE: The concentration of calcium, magnesium, sodium and
strontium in environmental waters, along with iron and
aluminum in solids can vary greatly and are not
necessarily predictable. Fortifying these analytes in
routine samples at the same concentration used for the
LFB may prove to be of little use in assessing data
quality for these analytes. For these analytes sample
dilution and reanalysis using the criteria given in
Section 9.5.2 is recommended. Also, if specified by
the data user, laboratory or program, samples can be
fortified at higher concentrations, but even major
constituents should be limited to < 25 mg/L so as not
to alter the sample matrix and affect the analysis.
9.4.3 Calculate the percent recovery for each analyte, corrected for
background concentrations measured in the unfortified sample,
and compare these values to the designated LFM recovery range
of 70-130% or a 3 sigma recovery ranqe calculated from the
regression equations given in Table 9. Recovery calculations
are not required if the concentration added is less than 30% of
the sample background concentration. Percent recovery may be
calculated in units appropriate to the matrix, using the
following equation:
R = x 100
s
200.7-26 Revision 4.4 May 1994
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where: R = percent recovery.
Cs = fortified sample concentration.
C = sample background concentration.
s = concentration equivalent of analyte
added to fortify the sample.
9.4.4 If the recovery of any analyte falls outside the designated LFM
recovery range, and the laboratory performance for that analyte
is shown to be in control (Sect. 9.3), the recovery problem
encountered with the fortified sample is judged to be matrix
related, not system related. The data user should be informed
that the result for that analyte in the unfortified sample is
suspect due to either the heterogeneous nature of the sample or
matrix effects and analysis by method of standard addition or
the use of an internal standard(s) (Sect. 11.5) should be
considered.
9.4.5 Where reference materials are available, they should be
analyzed to provide additional performance data. The analysis
of reference samples is a valuable tool for demonstrating the
ability to perform the method acceptably. Reference materials
containing high concentrations of analytes can provide
additional information on the performance of the spectral
interference correction routine.
9.5 Assess the possible need for the method of standard additions (MSA) or
internal standard elements by the following tests. Directions for
using MSA or internal standard(s) are given in Section 11.5.
9.5.1 Analyte addition test: An analyte(s) standard added to a
portion of a prepared sample, or its dilution, should be
recovered to within 85% to 115% of the known value. The
analyte(s) addition should produce a minimum level of 20 times
and a maximum of 100 times the method detection limit. If the
analyte addition is < 20% of the sample analyte concentration,
the following dilution test should be used. If recovery of the
analyte(s) is not within the specified limits, a matrix effect
should be suspected, and the associated data flagged
accordingly. The method of additions or the use of an
appropriate internal standard element may provide more accurate
data.
9.5.2 Dilution test: If the analyte concentration is sufficiently
high (minimally, a factor of 50 above the instrument detection
limit in the original solution but < 90% of the linear limit),
an analysis of a 1+4 dilution should agree (after correction
for the fivefold dilution) within ± 10% of the original
determination. If not, a chemical or physical interference
effect should be suspected and the associated data flagged
accordingly. The method of standard additions or the use of an
internal-standard element may provide more accurate data for
samples failing this test.
200.7-27 Revision4.4 May 1994
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10.0 CALIBRATION AND STANDARDIZATION
10.1 Specific wavelengths are listed in Table 1. Other wavelengths may be
substituted if they can provide the needed, sensitivity and are
corrected for spectral interference. However, because of the
difference among various makes and models of spectrometers, specific
instrument operating conditions cannot be given. The instrument and
operating conditions utilized for determination must be capable of
providing data of acceptable quality to the program and data user.
The analyst should follow the instructions provided by the instrument
manufacturer unless other conditions provide similar or better
performance for a task. Operating conditions for aqueous solutions
usually vary from 1100 to 1200 watts forward power, 15-to 16-mm
viewing height, 15 to 19 liters/min argon coolant flow, 0.6 to 1 L/min
argon aerosol flow, 1 to 1.8 mL/min sample pumping rate with a 1-min
preflush time and measurement time near 1 s per wavelength peak (for
sequential instruments) and near 10 s per sample (for simultaneous
instruments). Use of the Cu/Mn intensity ratio at 324.754 nm and
257.610 nm (by adjusting the argon aerosol flow) has been recommended
as a way to achieve repeatable interference correction factors.17
10.2 Prior to using this method optimize the plasma operating conditions.
The following procedure is recommended for vertically configured
plasmas. The purpose of plasma optimization is to provide a maximum
signal-to-background ratio for the least sensitive element in the
analytical array. The use of a mass flow controller to regulate the
nebulizer gas flow rate greatly facilitates the procedure.
10.2.1 Ignite the plasma and select an appropriate incident rf power
with minimum reflected power. Allow the instrument to become
thermally stable before beginning. This usually requires at
least 30 to 60 minutes of operation. While aspirating the
1000-AJg/mL solution of yttrium (Sect. 7.8.32), follow the
instrument manufacturer's instructions and adjust the aerosol
carrier gas flow rate through the nebulizer so a definitive
blue emission region of the plasma extends approximately from
5 to 20 mm above the top of the work coil. Record the
nebulizer gas flow rate or pressure setting for future
reference.
10.2.2 After establishing the nebulizer gas flow rate, determine the
solution uptake rate of the nebulizer in mL/min by aspirating
a known volume calibration blank for a period of at least 3
minutes. Divide the spent volume by the aspiration time (in
minutes) and record the uptake rate. Set the peristaltic pump
to deliver the uptake rate in a steady even flow.
10.2.3 After horizontally aligning the plasma and/or optically
profiling the spectrometer, use the selected instrument
conditions from Sections 10.2.1 and 10.2.2, and aspirate the
plasma solution (Sect. 7.15), containing 10 jLtg/mL each of As,
Pb, Se and Tl. Collect intensity data at the wavelength peak
for each analyte at 1 mm intervals from 14 to 18 mm above the
top of the work coil. (This region of the plasma is commonly
200.7-28 Revision 4.4 May 1994
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referred to as the analytical zone.) Repeat the process
using the calibration blank. Determine the net signal to blank
intensity ratio for each analyte for each viewing height
setting. Choose the height for viewing the plasma that provides
the largest intensity ratio for the least sensitive element of
the four analytes. If more than one position provides the same
ratio, select the position that provides the highest net
intensity counts for the least sensitive element or accept a
compromise position of the intensity ratios of all four
analytes.
10.2.4 The instrument operating condition finally selected as being
optimum should provide the lowest reliable instrument detection
limits and method detection limits. Refer to Tables 1 and 4
for comparison of IDLs and MDLs, respectively.
10.2.5 If either the instrument operating conditions, such as incident
power and/or nebulizer gas flow rate are changed, or a new
torch injector tube having a different orifice i.d. is
installed, the plasma and plasma viewing height should be
reoptimized.
10.2.6 Before daily calibration and after the instrument warmup
period, the nebulizer gas flow must be reset to the determined
optimized flow. If a mass flow controller is being used, it
should be reset to the recorded optimized flow rate. In order
; to maintain valid spectral interelement correction routines the
nebulizer gas flow rate should be the same from day-to-day (<2%
change). The change in signal intensity with a change in
nebulizer gas flow rate for both "hard" (Pb 220.353 nm) and
"soft" (Cu 324.754) lines is illustrated in Figure 1.
10.3 Before using the procedure (Section 11.0) to analyze samples, there
must be data available documenting initial demonstration of
performance. The required data and procedure is described in Section
9.2. This data must be generated using the same instrument operating
conditions and calibration routine (Sect. 11.4) to be used for sample
analysis. These documented data must be kept on file and be available
for review by the data user.
10.4 After completing the initial demonstration of performance, but before
analyzing samples, the laboratory must establish and initially verify
an interelement spectral interference correction routine to be used
during sample analysis. A general description concerning spectral
interference and the analytical requirements for background correction
and for correction of interelement spectral interference in particular
are given in Section 4.1. To determine the appropriate location for
background correction and to establish the interelement interference
correction routine, repeated spectral scan about the analyte
wavelength and repeated analyses of the single element solutions may
be required. Criteria for determining an interelement spectral
interference is an apparent positive or negative concentration on the
analyte that is outside the 3-sigma control limits of the calibration
blank for the analyte. (The upper-control limit is the analyte IDL.)
200.7-29 Revision 4.4 May 1994
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Once established, the entire routine must be initially and
periodically verified annually, or whenever there is a change in
instrument operating conditions (Sect 10.2.5). Only a portion of the
correction routine must be verified more frequently or on a daily
basis. Test criteria and required solutions are described in Section
7.13. Initial and periodic verification data of the routine should be
kept on file. Special cases where on-going verification are required
is described in Section 7.14.
11.0 PROCEDURE
11.1 Aqueous Sample Preparation - Dissolved Analytes
11.1.1 For the determination of dissolved analytes in ground and
surface waters, pipet an aliquot (> 20 ml) of the filtered,
acid preserved sample into a 50-mL polypropylene centrifuge
tube. Add an appropriate volume of (1+1) nitric acid to adjust
the acid concentration of the aliquot to approximate a 1% (v/v)
nitric acid solution (e.g., add 0.4 ml (1+1) HN03 to a 20 ml
aliquot of sample). Cap the tube and mix. The sample is now
ready for analysis (Sect. 1.3). Allowance for sample dilution
should be made in the calculations. (If mercury is to be
determined, a separate aliquot must be additionally acidified
to contain 1% (v/v) HC1 to match the signal response of mercury
in the calibration standard and reduce memory interference
effects. Sect. 1.9)
NOTE: If a precipitate is formed during acidification,
transport, or storage, the sample aliquot must be
treated using the procedure described in Sections
11.2.2 thru 11.2.7 prior to analysis.
11.2 Aqueous Sample Preparation - Total Recoverable Analytes
11.2.1 For the "direct analysis" of total recoverable analytes in
drinking water samples containing turbidity < 1 NTU, treat an
unfiltered acid preserved sample aliquot using the sample
preparation procedure described in Section 11.1.1 while making
allowance for sample dilution in the data calculation (Sect.
1.2). For the determination of total recoverable analytes in
all other aqueous samples or for preconcentrating drinking
water samples prior to analysis follow the procedure given in
Sections 11.2.2 through 11.2.7.
11.2.2 For the determination of total recoverable analytes in aqueous
samples (other than drinking water with < 1 NTU turbidity),
transfer a 100-mL (± 1 ml) aliquot from a well mixed, acid
preserved sample to a 250-mL Griffin beaker (Sects. 1.2, 1.3,
1.6, 1.7, 1.8, & 1.9). (When necessary, smaller sample aliquot
volumes may be used.)
NOTE: If the sample contains undissolved solids > 1%, a well
mixed, acid preserved aliquot containing no more than
1 g particulate material should be cautiously
200.7-30 Revision 4.4 May 1994
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evaporated to near 10 ml and extracted using the acid-
mixture procedure described in Sections 11.3.3 thru
11.3.6.
11.2.3 Add 2 ml (1+1) nitric acid and 1.0 ml of (1+1) hydrochloric
acid to the beaker containing the measured volume of sample.
Place the beaker on the hot plate for solution evaporation.
The hot plate should be located in a fume hood and previously
adjusted to provide evaporation at a temperature of
approximately but no higher than 85°C. (See the following
note.) The beaker should be covered with an elevated watch
glass or other necessary steps should be taken to prevent
sample contamination from the fume hood environment.
NOTE: For proper heating adjust the temperature control of
the hot plate such that an uncovered Griffin beaker
containing 50 ml of water placed in the center of the
hot plate can be maintained at a temperature
approximately but no higher than 85°C. (Once the beaker
is covered with a watch glass the temperature of the
water will rise to approximately 95°C.)
11.2.4 Reduce the volume of the sample aliquot to about 20 ml by
gentle heating at 85°C. DO NOT BOIL. This step takes about 2
h for a 100 ml aliquot with the rate of evaporation rapidly
increasing as the sample volume approaches 20 ml. (A spare
beaker containing 20 ml of water can be used as a gauge.)
11.2.5 Cover the lip of the beaker with a watch glass to reduce
additional evaporation and gently reflux the sample for 30
minutes. (Slight boiling may occur, but vigorous boiling must
be avoided to prevent loss of the HC1-H20 azeotrope.)
11.2.6 Allow the beaker to cool. Quantitatively transfer the sample
solution to a 50-mL volumetric flask, make to volume with
reagent water, stopper and mix.
11.2.7 Allow any undissolved material to settle overnight, or
centrifuge a portion of the prepared sample until clear. (If
after centrifuging or standing overnight the sample contains
suspended solids that would clog the nebulizer, a portion of
the sample may be filtered for their removal prior to analysis.
However, care should be exercised to avoid potential
contamination from filtration.) The sample is now ready for
analysis. Because the effects of various matrices on the
stability of diluted samples cannot be characterized, all
analyses should be performed as soon as possible after the
completed preparation.
11.3 Solid Sample Preparation - Total Recoverable Analytes
11.3.1 For the determination of total recoverable analytes in solid
samples, mix the sample thoroughly and transfer a portion
(> 20 g) to tared weighing dish, weigh the sample and record
200.7-31 Revision 4.4 May 1994
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the wet weight (WW). (For samples with < 35% moisture a 20 g
portion is sufficient. For samples with moisture > 35% a
larger aliquot 50-100 g is required.) Dry the sample to a
constant weight at 60°C and record the dry weight (DW) for
calculation of percent solids (Sect. 12.6). (The sample is
dried at 60°C to prevent the loss of mercury and other possible
volatile metallic compounds, to facilitate sieving, and to
ready the sample for grinding.)
11.3.2 To achieve homogeneity, sieve the dried sample using a 5-mesh
polypropylene sieve and grind in a mortar and pestle. (The
sieve, mortar and pestle should be cleaned between samples.)
From the dried, ground material weigh accurately a
representative 1.0 ± 0.01 g aliquot (W) of the sample and
transfer to a 250-mL Phillips beaker for acid extraction
(Sects.1.6, 1.7, 1.8, & 1.9).
11.3.3 To the beaker add 4 mL of (1+1) HN03 and 10 ml of (1+4) HC1.
Cover the lip of the beaker with a watch glass. Place the
beaker on a hot plate for reflux extraction of the analytes.
The hot plate should be located in a fume hood and previously
adjusted to provide a reflux temperature of approximately
95°C. (See the following note.)
NOTE: For proper heating adjust the temperature control of
the hot plate such that an uncovered Griffin beaker
containing 50 ml of water placed in the center of the
hot plate can be maintained at a temperature
approximately but no higher than 85°C. (Once the beaker
is covered with a watch glass the temperature of the
water will rise to approximately 95°C.) Also, a block
digester capable of maintaining a temperature of 95°C
and equipped with 250-mL constricted volumetric
digestion tubes may be substituted for the hot plate
and conical beakers in the extraction step.
11.3.4 Heat the sample and gently reflux for 30 min. Very slight
boiling may occur, however vigorous boiling must be avoided to
prevent loss of the HCl-H^O azeotrope. Some solution
evaporation will occur (3 to 4 ml).
11.3.5 Allow the sample to cool and quantitatively transfer the
extract to a 100-mL volumetric flask. Dilute to volume with
reagent water, stopper and mix.
11.3.6 Allow the sample extract solution to stand overnight to
separate insoluble material or centrifuge a portion of the
sample solution until clear. (If after centrifuging or
standing overnight the extract solution contains suspended
solids that would clog the nebulizer, a portion of the extract
solution may be filtered for their removal prior to analysis.
However, care should be exercised to avoid potential
contamination from filtration.) The sample extract is now
ready for analysis. Because the effects of various matrices on
200.7-32 Revi si on 4.4 May 1994
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the stability of diluted samples cannot be characterized, all
analyses should be performed as soon as possible after the
completed preparation.
11.4 Sample Analysis
11.4.1 Prior to daily calibration of the instrument inspect the sample
introduction system including the nebulizer, torch, injector
tube and uptake tubing for salt deposits, dirt and debris that
would restrict solution flow and affect instrument performance.
Clean the system when needed or on a daily basis.
11.4.2 Configure the instrument system to the selected power and
operating conditions as determined in Sections 10.1 and 10.2.
11.4.3 The instrument must be allowed to become thermally stable
before calibration and analyses. This usually requires at
least 30 to 60 minutes of operation. After instrument warmup,
complete any required optical profiling or alignment particular
to the instrument.
11.4.4 For initial and daily operation calibrate the instrument
according to the instrument manufacturer's recommended
procedures, using mixed calibration standard solutions (Sect.
7.9) and the calibration blank (Sect. 7.10.1). A peristaltic
pump must be used to introduce all solutions to the nebulizer.
To allow equilibrium to be reached in the plasma, aspirate all
solutions for 30 sec after reaching the plasma before beginning
integration of the background corrected signal to accumulate
data. When possible, use the average value of replicate
integration periods of the signal to be correlated to the
analyte concentration. Flush the system with the rinse blank
(Sect. 7.10.4) for a minimum of 60 seconds (Sect. 4.4) between
each standard. The calibration line should consist of a
minimum of a calibration blank and a high standard. Replicates
of the blank and highest standard provide an optimal
distribution of calibration standards to minimize the
confidence band for a straight-line calibration in a response
region with uniform variance.20
11.4.5 After completion of the initial requirements of this method
(Sects. 10.3 and 10.4), samples should be analyzed in the same
operational manner used in the calibration routine with the
rinse blank also being used between all sample solutions LFBs
LFMs, and check solutions (Sect. 7.10.4).
11.4.6 During the analysis of samples, the laboratory must comply with
the required quality control described in Sections 9.3 and 9.4.
Only for the determination of dissolved analytes or the "direct
analysis" of drinking water with turbidity of < 1 NTU is the
sample digestion step of the LRB, LFB, and LFM not required.
11.4.7 Determined sample analyte concentrations that are 90% or more
of the upper limit of the analyte LDR must be diluted with
200.7-33 Revision 4.4 May 1994
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reagent water that has been acidified in the same manner as
calibration blank and reanalyzed (see Sect. 11.4.8). Also, for
the interelement spectral interference correction routines to
remain valid during sample analysis, the interferant
concentration must not exceed its LDR. If the interferant LDR
is exceeded, sample dilution with acidified reagent water and
reanalysis is required. In these circumstances analyte
detection limits are raised and determination by another
approved test procedure that is either more sensitive and/or
interference free is recommended.
11.4.8 When it is necessary to assess an operative matrix interference
(e.g., signal reduction due to high dissolved solids), the
tests described in Section 9.5 are recommended.
11.4.9 Report data as directed in Section 12.
11.5 If the method of standard additions (MSA) is used, standards are added
at one or more levels to portions of a prepared sample. This
technique compensates for enhancement or depression of an analyte
signal by a matrix. It will not correct for additive interferences
such as contamination, interelement interferences, or baseline shifts.
This technique is valid in the linear range when the interference
effect is constant over the range, the added analyte responds the same
as the endogenous analyte, and the signal is corrected for additive
interferences. The simplest version of this technique is the single-
addition method. This procedure calls for two identical aliquots of
the sample solution to be taken. To the first aliquot, a small volume
of standard is added; while to the second aliquot, a volume of acid
blank is added equal to the standard addition. The sample
concentration is calculated by the following:
S2 x Y! x C
Sample Cone =
(rag/L or mg/kg) (SrS2) x V2
where: C « Concentration of the standard solution (mg/L)
S, * Signal for fortified aliquot
S2 = Signal for unfortified aliquot
V., = Volume of the standard addition (L)
V2 = Volume of the sample aliquot (L) used for MSA
For more than one fortified portion of the prepared sample, linear
regression analysis can be applied using a computer or calculator
program to obtain the concentration of the sample solution. An
alternative to using the method of standard additions is use of the
internal standard technique by adding one or more elements (not in the
samples and verified not to cause an uncorrected interelement spectral
interference) at the same concentration (which is sufficient for
optimum precision) to the prepared samples (blanks and standards) that
are affected the same as the analytes by the sample matrix. Use the
ratio of analyte signal to the internal standard signal for
calibration and quantitation.
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12.0 DATA ANALYSIS AND CALCULATIONS
12.1 Sample data should be reported in units of mg/L for aqueous samples
and mg/kg dry weight for solid samples.
12.2 For dissolved aqueous analytes (Sect. 11.1) report the data generated
directly from the instrument with allowance for sample dilution Do
not report analyte concentrations below the IDL.
12.3 For total recoverable aqueous analytes (Sect. 11.2), multiply solution
analyte concentrations by the dilution factor 0.5, when 100 mL aliquot
is used to produce the 50 mL final solution, and report data as
instructed in Section 12.4. If a different aliquot volume other than
100 mL is used for sample preparation, adjust the dilution factor
accordingly. Also, account for any additional dilution of the
prepared sample solution needed to complete the determination of
analytes exceeding 90% or more of the LDR upper limit. Do not report
data below the determined analyte MDL concentration or below an
adjusted detection limit reflecting smaller sample aliquots used in
processing or additional dilutions required to complete the analysis.
12.4 For analytes with MDLs < 0.01 mg/L, round the data values to the
thousandth place and report analyte concentrations up to three
significant figures. For analytes with MDLs > 0.01 mg/L round the
data values to the hundredth place and report analyte concentrations
up to three significant figures. Extract concentrations for solids
data should be rounded in a similar manner before calculations in
section 12.5 are performed.
12.5 For total recoverable analytes in solid samples (Sect. 11.3), round
the solution analyte concentrations (mg/L) as instructed in Section
1^.4. Report the data up to three significant figures as mq/kq drv-
weight basis unless specified otherwise by the program or data user.
calculate the concentration using the equation below:
C x V x D
Sample Cone, (mg/kg) =
dry-weight basis w
where: C = Concentration in extract (mg/L)
V = Volume of extract (L, 100 mL = 0.1L)
D = Dilution factor (undiluted = 1)
W = Weight of sample aliquot extracted (g x 0.001 = kg)
•M analyte data below the estimated solids MDL or an
adjusted MDL because of additional dilutions required to complete the
analysis.
12'6 folfows^ Percent solids in Sol1d samPlgs (Sect. 11.3) calculate as
200.7-35 Revision 4.4 May 1994
-------
DW
% solids (S) = x 100
WW
where: DW = Sample weight (g) dried at 60°C
WW = Sample weight (g) before drying
NOTE: If the data user, program or laboratory requires that the
reported percent solids be determined by drying at 105 C,
repeat the procedure given in Section 11.3 using a separate
portion (> 20 g) of the sample and dry to constant weight at
103-105°C.
12 7 The QC data obtained during the analyses provide an indication of the
quality of the sample data and should be provided with the sample
results.
13.0 METHOD PERFORMANCE
13.1 Listed in Table 4 are typical single laboratory total recoverable MDLs
determined for the recommended wavelengths using simultaneous ICP-AES
and the operating conditions given in Table 5. The MDLs were
determined in reagent blank matrix (best case situation). PTFE
beakers were used to avoid boron and silica contamination from
glassware with the final dilution to 50 mL completed in polypropylene
centrifuged tubes. The listed MDLs for solids are estimates and were
calculated from the aqueous MDL determinations.
13.2 Data obtained from single laboratory method testing are summarized in
Table 6 for five types of water samples consisting of drinking water,
surface water, ground water, and two wastewater effluents. The data
presented cover all analytes except cerium and titanium. Samples were
prepared using the procedure described in Sect. 11.2. For each
matrix, five replicate -aliquots were prepared, analyzed and the
average of the five determinations used to define the sample
background concentration of each analyte. In addition, two pairs of
duplicates were fortified at different concentration levels. For each
method analyte, the sample background concentration, mean percent
recovery, standard deviation of the percent recovery, and relative
percent difference between the duplicate fortified samples are listed
in Table 6. The variance of the five replicate sample background
determinations is included in the calculated standard deviation of the
percent recovery when the analyte concentration in the sample was
greater than the MDL. The tap and well waters were processed in
Teflon and quartz beakers and diluted in polypropylene centrifuged
tubes. The nonuse of borosilicate glassware is reflected in the
precision and recovery data for boron and silica in those two sample
types.
13.3 Data obtained from single laboratory method testing are summarized in
Table 7 for three solid samples consisting of EPA 884 Hazardous Soil,
SRM 1645 River Sediment, and EPA 286 Electroplating Sludge. Samples
were prepared using the procedure described in Sect. 11.3. For each
method analyte, the sample background concentration, mean percent
200.7-36 Revision 4.4 May 1994
-------
recovery of the fortified additions, the standard deviation of the
percent recovery, and relative percent difference between duplicate
additions were determined as described in Sect. 13.2. Data presented
are for all analytes except cerium, silica and titanium. Limited
comparative data to other methods and SRM materials are presented in
reference 23 of Section 16.0.
13.4 Performance data for aqueous solutions independent of sample
preparation from a multi laboratory study are provided in Table 8/2
13.5 Listed in Table 9 are regression equations for precision and bias for
25 analytes abstracted from EPA Method Study 27, a multi laboratory
validation study of Method 200. 7. 1 These equations were developed
from data received from 12 laboratories using the total recoverable
sample preparation procedure on reagent water, drinking water, surface
water and 3 industrial effluents. For a complete review and
description of the study see reference 16 of Section 16.0.
14.0 POLLUTION PREVENTION
14.1 Pollution prevention encompasses any technique that reduces or
eliminates the quantity or toxicity of waste at the point of
generation. Numerous opportunities for pollution prevention exist in
laboratory operation. The EPA has established a preferred hierarchy
of environmental management techniques that places pollution
prevention as the management option of first choice. Whenever
feasible, laboratory personnel should use pollution prevention
techniques to address their waste generation (e.g., Sect. 7.8) When
wastes cannot be feasibly reduced at the source, the Agency recommends
recycling as the next best option.
14.2 For information about pollution prevention that may be applicable to
aboratones and research institutions, consult Less is Better-
Laboratory Chemical Management for Haste Reduction, available from the
American Chemical Society's Department of Government Relations and
N'W" Washin9ton D'C- 20036,
15.0 WASTE MANAGEMENT
15.1 The Environmental Protection Agency requires that laboratory waste
management practices be conducted consistent with all applicable rules
and regulations. The Agency urges laboratories to protect the air
water, and land by minimizing and controlling all releases from hoods
and bench operations, complying with the letter and spirit of any
sewer discharge permits and regulations, and by complying with all
solid and hazardous waste regulations, particularly the hazardous
waste identification rules and land disposal restrictions. For
further information on waste management consult The Haste Management
Manual for Laboratory Personnel, available from the American Chemical
Society at the address listed in the Section 14.2.
200.7-37 Revision 4. 4 May 1994
-------
16.0 REFERENCES
1. U.S. Environmental Protection Agency. Inductively Coupled Plasma-
Atomic Emission Spectrometric Method for Trace Element Analysis of
Water and Wastes-Method 200.7, Dec. 1982. EPA-600/4-79-020, revised
March 1983.
2 U.S. Environmental Protection Agency. Inductively Coupled Plasma
Atomic Emission Spectroscopy Method 6010, SW-846 Test Methods for
Evaluating Solid Waste, 3rd Edition, 1986.
3 U.S. Environmental Protection Agency. Method 200.7: Determination of
Metals and Trace Elements in Water and Wastes by Inductively Coupled
Plasma-Atomic Emission Spectrometry, revision 3.3, EPA 600 4-91/010
June 1991.
4. U.S. Environmental Protection Agency. Inductively Coupled Plasma -
Atomic Emission Spectrometry Method for the Analysis of Waters and
Solids, EMMC, July 1992.
5. Fassel, V.A. et al. Simultaneous Determination of Wear Metals in
Lubricating Oils by Inductively-Coupled Plasma Atomic Emission
Spectrometry. Anal. Chem. 48:516-519, 1976.
6. Merryfield, R.N. and R.C. Loyd. Simultaneous Determination of Metals
in Oil by Inductively Coupled Plasma Emission Spectrometry. Anal.
Chem. 51:1965-1968, 1979.
7. Winge, R.K. et al. Inductively Coupled Plasma-Atomic Emission
Spectroscopy: An Atlas of Spectral Information, Physical Science Data
20. Elsevier Science Publishing, New York, New York, 1985.
8. Boumans, P.W.J.M. Line Coincidence Tables for Inductively Coupled
Plasma Atomic Emission Spectrometry, 2nd edition. Pergamon Press,
Oxford, United Kingdom, 1984.
9. Carcinogens - Working With Carcinogens, Department of Health,
Education, and Welfare, Public Health Service, Center for Disease
Control, National Institute for Occupational Safety and Health,
Publication No. 77-206, Aug. 1977. Available from the National
Technical Information Service (NTIS) as PB-277256.
10. OSHA Safety and Health Standards, General Industry, (29 CFR
1910), Occupational Safety and Health Administration, OSHA 2206,
(Revised, January 1976).
11. Safety in Academic Chemistry Laboratories, American Chemical
Society Publication, Committee on Chemical Safety, 3rd Edition,
1979.
12. Proposed OSHA Safety and Health Standards, Laboratories, Occupational
Safety and Health Administration, Federal Register, July 24, 1986.
200.7-38 Revision4.4 May 1994
-------
13. Rohrbough, W.G. et al. Reagent Chemicals, American Chemical Society
Specifications, 7th edition. American Chemical Society, Washington,
DC, 1986.
14. American Society for Testing and Materials. Standard Specification
for Reagent Water, D1193-77. Annual Book of ASTM Standards, Vol
11.01. Philadelphia, PA, 1991.
15. Code of Federal Regulations 40, Ch. 1, Pt, 136 Appendix B.
16. Maxfield, R. and b. Mindak. EPA Method Study 27, Method 200.7 Trace
Metals by ICP, Nov. 1983. Available from National Technical
Information Service (NTIS) as PB 85-248-656.
17. Botto, R.I. Quality Assurance in Operating a Multielement ICP
Emission Spectrometer. Spectrochim. Acta, 39B(1):95-113, 1984.
18. Wallace, G.F., Some Factors Affecting the Performance of an ICP Sample
Introduction System. Atomic Spectroscopy, Vol. 4, p. 188-192, 1983.
19. Koirtyohann, S.R. et al. Nomenclature System for the Low-Power Arqon
Inductively Coupled Plasma, Anal. Chem. 52:1965, 1980
20. Deming, S.N. and S.L. Morgan. Experimental Design for Quality and
Productivity in Research, Development, and Manufacturing, Part III DD
119-123. Short course publication by Statistical Designs, 9941
Rowlett, Suite 6, Houston, TX 77075, 1989.
21. Winefordner, J.D., Trace Analysis: Spectroscopic Methods for
Elements, Chemical Analysis, Vol. 46, pp. 41-42.
22. Jones, C.L. et al. An Interlaboratory Study of Inductively Coupled
Plasma Atomic Emission Spectroscopy Method 6010 and Digestion Method
3050. EPA-600/4-87-032, U.S. Environmental Protection Agency, Las
Vegas, Nevada, 1987.
23. Martin, T.D., E.R. Martin and S.E. Long. Method 200.2: Sample
Preparation Procedure for Spectrochemical Analyses nf Total
Recoverable Elements. FMSI nRn; IISFP/J IQSQ
200.7-39 Revision 4.4 May 1994
-------
17.0 TABLES. DIAGRAMS. FLOWCHARTS. AND VALIDATION DATA
TABLE I: WAVELENGTHS, ESTIMATED INSTRUMENT DETECTION
LIMITS, AND RECOMMENDED CALIBRATION
Analyte
Aluminum
Antimony
Arsenic
Barium
Beryl 1 i urn
Boron
Cadmium
Calcium
Cerium
Chromium
Cobalt
Copper
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Phosphorus
Potassium
Selenium
Silica (Si02)
Silver
Sodium
Strontium
Thallium
Tin
Titanium
Vanadium
Zinc
Wavelength3
(nm)
308.215
206.833
193.759
493.409
313.042
249.678
226.502
315.887
413.765
205.552
228.616
324.754
259.940
220.353
670.784
279.079
257.610
194.227
203.844
231.604
214.914
766.491
196.090
251.611
328.068
588.995
421.552
190.864
189.980
334.941
292.402
213.856
Estimated
Detection
Limitb
(09/L)
45
32
53
2.3
0.27
5.7
3.4
30
48
6.1
7.0
5.4
6.2
42
3.7d
30
1.4
2.5
12
15
76
_ p
700e
75H
26d (Si02)
7.0
29
0.77
40
25
3.8
7.5
1.8
Calibrate0
to
(mg/L)
10
5
10
1
1
1
2
10
2
5
2
2
10
10
5
10
2
2
10
2
10
20
5
10
0.5
10
1
5
4
10
2
5
a The wavelengths listed are recommended because of their sensitivity and
overall acceptability. Other wavelengths may be substituted if they can
provide the needed sensitivity and are treated with the same corrective
techniques for spectral interference (see Section 4.1).
b These estimated 3-sigma instrumental detection limits16 are provided
only as a guide to instrumental limits. The method detection limits are
200.7-40
Revision 4.4 May 1994
-------
sample dependent and may vary as the sample matrix varies. Detection
limits for solids can be estimated by dividing these values by the qrams
extracted per liter, which depends upon the extraction procedure. Divide
solution detection limits by 10 for 1 g extracted to 100 ml for solid
detection limits.
c Suggested concentration for instrument calibration.2 Other calibration
limits in the linear ranges may be used.
Calculated from 2-sigma data.5
Q
Highly dependent on operating conditions and plasma position.
200.7-41 Revi si on 4.4 May 1994
-------
TABLE 2: ON-LINE METHOD INTERELEMENT SPECTRAL INTERFERENCES
ARISING FROM INTERFERANTS AT THE 100-mg/L LEVEL
Analyte
Ag
Al
As
B
Ba
Be
Ca
Cd
Ce
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
P
Pb
Sb
Se
SiO,
Sn 2
Sr
Tl
Ti
V
Zn
Wavelength
(nm)
328.068
308.215
193.759
249.678
493.409
313.042
315.887
226.502
413.765
228.616
205.552
324.754
259.940
194.227
766.491
670.784
279.079
257.610
203.844
588.995
231.604
214.914
220.353
206.833
196.099
251.611
189.980
421.552
190.864
334.941
292.402
213.856
Interferant*
Ce,Ti,Mn
V,Mo,Ce,Mn
V,Al,Co,Fe,Ni
None
None
V,Ce
Co,Mo,Ce
Ni,Ti,Fe,Ce
None
Ti,Ba,Cd,Ni,Cr,Mo,Ce
Be,Mo,Ni,
Moji
None
V,Mo
None
None
Ce
Ce
Ce
None
Co,Tl
Cu,Mo
Co,Al,Ce,Cu,Ni,Ti,Fe
Cr,Mo,Sn,Ti,Ce,Fe
Fe
None
Mo,Ti,Fe,Mn,Si
None
Ti,Mo,Co,Ce,Al,V,Mn
None
Mo,Ti,Cr,Fe,Ce
Ni,Cu,Fe
* These on-line interferences from method analytes and titanium only were
observed using an instrument with 0.035-nm resolution (see Sect. 4.1.2).
Interferant ranked by magnitude of intensity with the most severe interferant
listed first in the row.
200.7-42 Revi si on 4.4 May 1994
-------
TABLE 3: MIXED STANDARD SOLUTIONS
Solution Analytes
I Ag, As, B, Ba, Ca, Cd, Cu, Mn, Sb, and Se
II K, Li, Mo, Na, Sr, and Ti
III Co, P, V, and Ce
IV Al, Cr, Hg, Si02, Sn, and Zn
V Be, Fe, Mg, Ni, Pb, and Tl
200.7-43 Revi si on 4.4 May 1994
-------
TABLE 4: TOTAL RECOVERABLE METHOD DETECTION LIMITS (MDL)
Anal vte
Ag
Al
As
B
Ba
Be
Ca
Cd
Ce
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
P
Pb
Sb
Se
Si Op
Sn 2
Sr
Ti
Tl
V
Zn
Aaueous. ma/L(1)
0.002
0.02
0.008
0.003
0.001
0.0003
0.01
0.001
0.02
0.002
0.004
0.003
0.03*
0.007
0.3
0.001
0.02
0.001
0.004
0.03
0.005
0.06
0.01
0.008
0.02
0.02
0.007
0.0003
0.001
0.02
0.003
0.002
MDLs
Solids. mq/ka(2)
0.3
3
2
—
0.2
0.1
2
0.2
3 -
0.4
0.8
0.5
6
2
60
0.2
3
0.2
1
6
1
12
2
2
5
—
2
0.1
0.2
3
1
0.3
7l) MDL concentrations are computed for original matrix with allowance for 2x
sample preconcentration during preparation. Samples were processed in PTFE
and diluted in 50-mL plastic centrifuge tubes.
(2) Estimated, calculated from aqueous MDL determinations.
Boron not reported because of glassware contamination.
Silica not determined in solid samples.
* Elevated value due to fume-hood contamination.
200.7-44 Revision 4.4 May 1994
-------
TABLE 5: INDUCTIVELY COUPLED PLASMA INSTRUMENT OPERATING CONDITIONS
Incident rf power
Reflected rf power
Viewing height above
work coil
Injector tube orifice i.d.
Argon supply
'Argon pressure
Coolant argon flow rate
Aerosol carrier argon
flow rate
Auxiliary (plasma)
argon flow rate
Sample uptake rate
controlled to
1100 watts
< 5 watts
15 mm
1 mm
liquid argon
40 psi
19 L/min
620 mL/min
300 mL/min
1.2 mL/min
200.7-45
Revision 4.4 May 1994
-------
TABLE 6: PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES
TAP WATER
ANALYTE
Ag
* *D
Al
As
B
Ba
Be
Ca
Cd
Co
Cr
Cu
Fe
Hg
i *y
K
Li
Ma
1 'y
Mn
Mo
Na
Ni
p
Pb
Sb
Se
sio2
Sn
Sr
Tl
V
Zn
SAMPLE LOW
CONC SPIKE
mg/L mg/L
<0.002
0.185
<0.008
0.023
0.042
<0.0003
35.2
<0.001
<0.002
<0.004
<0.003
0.008
<0.007
1.98
0.006
8.08
<0.001
<0.004
10.3
<0.005
0.045
<0.01
<0.008
<0.02
6.5
<0.007
0.181
<0.02
<0.003
0.005
0.05
0.05
0.05
0.1
0.05
0.01
5.0
0.01
0.02
0.01
0.02
0.1
0.05
5.0
0.02
5.0
0.01
0.02
5.0
0.02
0.1
0.05
0.05
0.1
5.0
0.05
0.1
0.1
0.05
0.05
AVERAGE
RECOVERY
R(%)
95
98
108
98
102
100
101
105
100
110
103
106
103
109
103
104
100
95
99
108
102
95
99
87
104
103
102
101
101
101
S(R)
0.7
8.8
1.4
0.2
1.6
0.0
8.8
3.5
0.0
0.0
1.8
1.0
0.7
1.4
6.9
2.2
0.0
3.5
3.0
1.8
13.1
0.7
0.7
1.1
3.3
2.1
3.3
3.9
0.7
3.7
HIGH
SPIKE
RPD mg/L
2.1
1.7
3.7
0.0
2.2
0.0
1.7
9.5
0.0
0.0
4.9
1.8
1.9
2.3
3.8
1.5
0.0
10.5
2.0
4.7
9.4
2.1
2.0
3.5
3.4
5.8
2.1
10.9
2.0
9.0
0.2
0.2
0.2
0.4
0.2
0.1
20.0
0.1
0.2
0.1
0.2
0.4
0.2
20.0
0.2
20.0
0.1
0.2
20.0
0.2
0.4
0.2
0.2
0.4
20.0
0.2
0.4
0.4
0.2
0.2
AVERAGE
RECOVERY
R(%)
96
105
101
98
98
99
103
98
99
102
101
105
100
107
110
100
99
108
106
104
104
100
102
99
96
101
105
101
99
98
S(R)
0.0
3.0
0.7
0.2
0.4
0.0
2.0
0.0
0.5
0.0
1.2
0.3
0.4
0.7
1.9
0.7
0.0
0.5
1.0
1.1
3.2
0.2
0.7
0.8
1.1
1.8
0.8
0.1
0.2
0.9
RPD
0.0
3.1
2.0
0.5
0.8
0.0
0.9
0.0
1.5
0.0
3.5
0.5
1.0
1.7
4.4
1.1
0.0
1.4
1.6
2.9
1.3
0.5
2.0
2.3
2.3
5.0
1.0
0.3
0.5
2.5
S(R) Standard deviation of percent recovery.
RPD Relative percent difference between duplicate spike determinations.
< Sample concentration below established method detection limit.
* Spike concentration <10% of sample background concentration.
200.7-46
Revision 4.4 May 1994
-------
TABLE 6: PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont'd.)
POND WATER
SAMPLE LOW
CONC SPIKE
ANALYTE mg/L mg/L
Ag
Al
As
B
Ba
Be
Ca
Cd
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
P
Pb
Sb
Se
Si02
Sn
Sr
Tl
V
In
S(R)
RPD
<0.002
0.819
<0.008
0.034
0.029
<0.0003
53.9
<0.001
<0.002
<0.004
0.003
0.875
<0.007
2.48
<0.001
10.8
0.632
<0.004
17.8
<0.005
0.196
<0.01
<0.008
<0.02
7.83
<0.007
0.129
<0.02
0.003
0.006
0.05
0.2
0.05
0.1
0.05
0.01
5
0.01
0.02
0.01
0.02
0.2
0.05
5
0.02
5
0.01
0.02
5
0.02
0.1
0.05
0.05
0.1
5
0.05
0.1
0.1
0.05
0.05
Standard deviation
AVERAGE
RECOVERY
R(%)
92
88
102
111
96
95
*
107
100
105
98
95
97
106
110
102
*
105
103
96
91
96
102
104
151
98
105
103
94
97
of percent
Relative percent difference b
S(R)
0.0
10.0
0.0
8.9
0.9
0.4
*
0.0
2.7
3.5
2.1
8.9
3.5
0.3
0.0
0.5
*
3.5
1.3
5.6
14.7
2.6
2.8
2.1
1.6
0.0
0.4
1.1
0.4
1.6
HIGH
SPIKE
RPD mg/L
0.0
5.0
0.0
6.9
0.0
1.1
0.7
0.0
7.5
9.5
4.4
2.8
10.3
0.1
0.0
0.0
0.2
9.5
0.4
9."1
0.3
7.8
7.8
5.8
1.3
0.0
0.0
2.9
0.0
1.8
0.2
0.8
0.2
0.4
0.2
0.1
20.0
0.1
0.2
0.1
0.2
0.8
0.2
20.0
0.2
20.0
0.1
0.2
20.0
0.2
0.4
0.2
0.2
0.4
20.0
0.2
0.4
0.4
0.2
0.2
AVERAGE
RECOVERY
94
100
98
103
97
95
100
97
97
103
100
97
98
103
106
96
97
103
94
100
108
100
104
103
117
99
99
97
98
94
S(R)
0.0
2.9
1.4
2.0
0.3
0.0
2.0
0.0
0.7
1.1
0.5
3.2
0.0
0.2
0.2
0.7
2.3
0.4
0.3
0.7
3.9
0.7
0.4
1.6
0.4
1.1
0.1
1.3
0.1
0.4
RPD
0.0
3.7
4.1
0.0
0.5
0.0
1.5
0.0
2.1
2.9
1.5
3.6
0.0
0.4
0.5
1.3
0.3
1.0
0.0
1.5
1.3
2.0
1.0
4.4
0.6
3.0
0.2
3.9
0.0
0.0
recovery.
etween
duplicate soike
determin,
3t.inn.<;.
Sample concentration below established method detection limit.
Spike concentration <10% of sample*background concentration.
200.7-47
Revision 4.4 May 1994
-------
TABLE 6: PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont'd.)
HELL HATER
SAMPLE
CONC
ANALYTE mg/L
LOW AVERAGE
SPIKE RECOVERY
mg/L R(%) S(R)
RPD
HIGH AVERAGE
SPIKE RECOVERY
mg/L R(%) S(R)
RPD
Ag
Al
As
B
Ba
Be
Ca
Cd
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
P
Pb
Sb
Se
Sn
Sr
Tl
V
Zn
S(R)
RPD
<
*
<0.002
0.036
<0.008
0.063
0.102
<0.0003
93.8
0.002
<0.002
<0.004
0.005
0.042
<0.007
6.21
0.001
24.5
2.76
<0.004
35.0
<0.005
0.197
<0.01
<0.008
<0.02
> 13.1
<0.007
0.274
<0.02
<0.003
0.538
0.05
0.05
0.05
0.1
0.05
0.01
5.0
0.01
0.02
0.01
0.02
0.1
0.05
5.0
0.02
5.0
0.01
0.02
5.0
0.02
0.1
0.05
0.05
0.1
5.0
0.05
0.1
0.1
0.05
0.05
97
107
107
97
102
100
*
90
94
100
100
99
94
96
100
95
*
108
101
112
95
87
98
102
93
98
94
92
98
*
0.7
7.6
0.7
0.6
3.0
0.0
*
0.0
0.4
7.1
1.1
2.3
2.8
3.4
7.6
5.6
*
1.8
11.4
1.8
12.7
4.9
2.8
0.4
4.8
2.8
5.7
0.4
0.0
*
2
10
1
0
0
0
2
0
1
20
0
1
8
3
9
0
0
4
0
4
1
16
8
1
2
8
2
1
0
0
.1
.1
.9
.7
.'0
.0
.1
.0
.1
.0
.4
.4
.5
.6
.5
.3
.4
.7
.8
.4
.9
.1
.2
.0
.8
.2
.7
.1
.0
.7
0.2
0.2
0.2
0.4
0.2
0.1
20.0
0.1
0.2
0.1
0.2
0.4
0.2
20.0
0.2
20.0
0.1
0.2
20.0
0.2
0.4
0.2
0.2
0.4
20.0
0.2
0.4
0.4
0.2
0.2
96
101
104
98
99
100
100
96
94
100
96
97
93
101
104
93
*
101
100
96
98
95
99
94
99
94
95
95
99
99
0
1
0
0
0
0
4
0
0
0
0
1
1
1
1
1
0
3
0
3
0
1
1
0
0
1
1
0
2
.2
.1
.4
.8
.9
.0
.1
.0
.4
.4
.5
.4
.2
.2
.0
.6
*
.2
.1
.2
.4
.2
.4
.1
.8
.2
.7
.1
.4
.5
0.5
0.8
1.0
2.1
1.0
0.0
0.1
0.0
1.1
1.0
1.5
3.3
3.8
2.3
1.9
1.2
0.7
0.5
1.5
0.5
0.9
0.5
4.0
3.4
0.0
0.5
2.2
3.2
1.0
1.1
Standard deviation of percent recovery.
Relative percent difference
Sample concentration
Spike concentration
below
<10% of
between dupl
establi
sample
icate spike
determinati
ons.
shed method detection limit.
background concentration.
200.7-48
Revision 4.4 May 1994
-------
TABLE 6: PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont'd.)
SEWAGE TREATMENT PRIMARY EFFLUENT
SAMPLE LOW
CONC SPIKE
AVERAGE
RECOVERY
ANALYTE mg/L mg/L R(%)
Ag
Al
As
B
Ba
Be
Ca
Cd
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
P
Pb
Sb
Se
Sn
Sr
Tl
V
Zn
S(R)
RPD
0.009
1.19
<0.008
0.226
0.189
<0.0003
87.9
0.009
0.016
0.128
0.174
1.28
<0.007
10.6
0.011
22.7
0.199
0.125
236
0.087
4.71
0.015
<0.008
<0.02
> 16.7
0.016
0.515
<0.02
0.003
0.160
0.05
0.05
0.05
0.1
0.05
0.01
5.0
0.01
0.02
0.01
0.02
0.1
0.05
5.0
0.02
5.0
0.01
0.02
5.0
0.02
0.1
0.05
0.05
0.1
5.0
0.05
0.1
0.1
0.05
0.05
Standard deviation
92
*
99
217
90
94
*
89
95
*
98
*
102
104
103
100
*
110
*
122
*
91
97
108
124
90
103
105
93
98
of percent
S(R)
1.5
*
2.1
16.3
6.8
0.4
*
2.6
3.1
*
33.1
*
1.4
2.8
8.5
4.4
*
21.2
*
10.7
*
3.5
0.7
3.9
4.0
3.8
6.4
0.4
0.9
3.3
recovery
Relative percent difference between du
HIGH
SPIKE
RPD mg/L
3.6
0.9
6.1
9.5
1.7
1.1
0.6
2.3
0.0
1.5
4.7
2.8
3.9
1.3
3.2
0.0
2.0
6.8
0.0
4.5
2.6
5.0
2.1
10.0
0.9
0.0
0.5
1.0
2.0
1.9
0.2
0.2
0.2
0.4
0:2
0.1
20.0
0.1
0.2
0.1
0.2
0.4
0.2
20.0
0.2
20.0
0.1
0.2
20.0
0.2
0.4
0.2
0.2
0.4
20.0
0.2
0.4
0.4
0.2
0.2
«
AVERAGE
RECOVERY
R(%)
95
113
93
119
99
100
101
97
93
97
98
111
98
101
105
92
104
102
*
98
*
96
103
101
108
95
96
95
97
101
S(R)
0.1
12.4
2.1
•13.1
1.6
0.4
3.7
0.4
0.4
2.4
3.0
7.0
0.5
0.6
0.8
1.1
1.9
1.3
*
0.8
*
1.3
1.1
2.6
1.1
1.0
1.6
0.0
0.2
1.0
RPD
0.0
2.1
6.5
20.9
0.5
1.0
0.0
1.0
0.5
2.7
1.4
0.6
1.5
0.0
0.5
0.2
0.3
0.9
0.4
1.1
1.4
2.9
2.9
7.2
0.8
0.0
0.2
0.0
0.5
1.4
plicate spike determinations.
Sample concentration below established method detection limit.
Spike concentration <10% of sample background concentration.
200.7-49
Revision 4.4 May 1994
-------
TABLE 6: PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont'd.)
INDUSTRIAL EFFLUENT
SAMPLE LOW
CONC SPIKE
AVERAGE
RECOVERY
ANALYTE mg/L mg/L R(%)
Ag
Al
As
B
Ba
Be
Ca
Cd
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
P
Pb
Sb
Se
Sn
Sr
Tl
V
Zn
S(R)
RPD
<0.003
0.054
<0.02
0.17
0.083
<0.0006
500
0.008
<0.004
0.165
0.095
0.315
<0.01
2.87
0.069
6.84
0.141
1.27
1500
0.014
0.326
0.251
2.81
0.021
> 6.83
<0.01
6.54
<0.03
<0.005
0.024
0.05
0.05
0.05
0.1
0.05
0.01
5.0
0.01
0.02
0.01
0.02
0.1
0.05
5.0
0.02
5.0
0.01
0.02
5.0
0.02
0.1
0.05
0.05
0.1
5.0
0.05
0.1
0.1
0.05
0.05
Standard deviation
88
88
82
162
86
94
*
85
93
*
93
88
87
101
103
87
*
*
*
98
105
80
*
106
99
87
*
87
90
89
of percent
S(R)
0.0
11.7
2.8
17.6
8.2
0.4
*
4.7
1.8
*
23.3
16.4
0.7
3.4
24.7
3.1
*
*
*
4.4
16.0
19.9
*
2.6
6.8
0.7
*
1.8
1.4
6.0
HIGH
SPIKE
RPD mg/L
0.0
12.2
9.8
13.9
1.6
1.1
2.8
6.1
5.4
4.5
0.9
1.0
2.3
2.4
5.6
0.0
1.2
0.0
2.7
3.0
4.7
1.4
0.4
3.2
1.7
2.3
2.0
5.8
4.4
4.4
0.2
0.2
0.2
0.4
0.2
0.1
20.0
0.1
0.2
0.1
0.2
0.4
0.2
20.0
0.2
20.0
0.1
0.2
20.0
0.2
0.4
0.2
0.2
0.4
20.0
0.2
0.4
0.4
0.2
0.2
AVERAGE
RECOVERY
R(%)
84
90
88
92
85
82
*
82
83
106
95
99
86
100
104
87
89
100
*
87
97
88
*
105
100
86
*
84
84
91
S(R)
0.9
3.9
0.5
4.7
2.3
1.4
*
1.4
0.4
6.6
2.7
6.5
0.4
0.8
2.5
0.9
6.6
15.0
*
0.5
3.9
5.0
*
1.9
2.2
0.4
*
1.1
1.1
3.5
RPD
3.0
8.1
1.7
9.3
2.4
4.9
2.3
4.4
1.2
5.6
2.8
8.0
1.2
0.4
2.2
1.2
4.8
2.7
2.0
1.1
1.4
0.9
2.0
4.6
3.0
1.2
2.7
3.6
3.6
8.9
recovery.
Relative percent difference between
duplicate spike
determi
nations.
Sample concentration below established method detection limit.
Spike concentration <10% of sample background concentration.
200.7-50
Revision 4.4 May 1994
-------
TABLE 7: PRECISION AND RECOVERY DATA IN SOLID MATRICES
EPA HAZARDOUS SOIL #884
ANALYTE
Ag
Al
As
B
Ba
Be
Ca
Cd
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
P
Pb
Sb
Se
Sn
Sr
Tl
V
Zn
S(R)
RPD
SAMPLE LOW+
CONC SPIKE
mg/kg mg/kg
1.1
5080
5.7
20.4
111
0.66
85200
2
5.5
79.7
113
16500
<1.4
621
6.7
24400
343
5.3
195
15.6
595
145
6.1
<5
16.6
102
<4
16.7
131
20
20
20
100
20
20
-
20
20
20
20
-
10
500
10
500
20
20
500
20
500
20
20
20
20
100
20
20
20
Standard deviation
AVERAGE
RECOVERY
R(%)
98
*
95
93
98
97
-
93
96
87
110
-
92
121
113
*
*
88
102
100
106
88
83
79
91
84
92
104
103
of percent
S(R)
0.7
*
5.4
2.7
71.4
0.7
-
0.7
3.5
28.8
16.2
-
2.5
1.3
3.5
*
*
5.3
2.2
1.8
13.4
51.8
3.9
14.7
34.6
9.6
4.8
4.2
31.2
HIGH+
SPIKE
RPD mg/kg
1.0
7.2
10.6
5.3
22.2
2.0
-
1.0
7.7
16.5
4.4
-
7.7
0.0
4.4
8.4
8.5
13.2
2.4
0.0
8.0
17.9
7.5
52.4
5.8
10.8
14.6
5.4
7.3
100
100
100
400
100
100
-
100
100
100
100
-
40
2000
40
2000
100
100
2000
100
2000
100
100
100
80
400
100
100
100
AVERAGE
RECOVERY
R(*)
96
*
96
100
97
99
-
94
93
104
104
-
98
107
106
*
95
91
100
94
103
108
81
99
112
94
91
99
104
S(R)
0.2
*
1.4
2.1
10.0
0.1
-
0.2
0.8
1.3
4.0
-
0.0
0.9
0.6
*
11.0
1.4
1.5
1.5
3.2
15.6
1.9
0.7
8.7
2.5
1.5
0.8
7.2
RPD
0.6
5.4
3.6
5.5
1.0
0.2
-
0.4
2.1
1.1
4.2
-
0.0
1.8
0.6
10.1
1.6
4.1
3.7
3.6
2.7
17.4
5.9
2.1
2.8
4.6
4.6
1.7
6.4
recovery.
Relative percent difference between
duplicate spike
determinations.
Sample concentration below established method detection limit.
Spike concentration <10% of sample background concentration.
Not spiked.
Equivalent
200.7-51
Revision 4.4 May 1994
-------
TABLE 7: PRECISION AND RECOVERY DATA IN SOLID MATRICES (Cont.)
EPA ELECTROPLATING SLUDGE #286
ANALYTE
Ag
Al
As
B
Ba
Be
Ca
Cd
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
P
Pb
Sb
Se
Sn
Sr
Tl
V
Zn
S(R)
RPD
SAMPLE LOW+
CONC SPIKE
mg/kg mg/kg
6
4980
32
210
39.8
0.32
48500
108
5.9
7580
806
31100
6.1
2390
9.1
1950
262
13.2
73400
456
9610
1420
<2
6.3
24.0
145
16
21.7
12500
20
20
20
100
20
20
-
20
20
20
20
-
10
500
10
500
20
20
500
20
500
20
20
20
20
100
20
20
20
Standard deviation
AVERAGE
RECOVERY
R(%)
96
*
94
113
0
96
-
98
93
*
*
-
90
75
101
110
*
92
*
*
*
*
76
86
87
90
89
95
*
of percent
S(R)
0.2
*
1.3
2.0
6.8
0.2
-
2.5
2.9
*
*
-
2.5
8.3
2.8
2.0
*
2.1
*
*
*
*
0.9
9.0
4.0
8.1
4.6
1.2
*
HIGH+
SPIKE
RPD mg/kg
0.4
4.4
0.8
1.6
0.3
0.5
-
0.8
5.7
0.7
1.5
-
4.0
4.0
0.5
0.8
1.8
2.9
1.7
0.4
2.9
2.1
3.3
16.6
2.7
8.1
5.3
1.0
0.8
100
100
100
400
100
100
-
100
100
100
100
-
40
2000
40
2000
100
100
2000
100
2000
100
100
100
100
400
100
100
100
AVERAGE
RECOVERY
R(%)
93
*
97
98
0
101
-
96
93
*
94
-
97
94
106
108
91
92
*
88
114
*
75
103
92
93
92
96
*
S(R)
0.1
*
0.7
1.9
1.6
0.7
-
0.5
0.6
*
8.3
-
1.7
2.9
1.6
2.3
1.2
0.3
*
2.7
7.4
*
2.8
1.6
0.7
2.4
0.8
0.4
*
RPD
0.4
5.6
1.6
3.5
5.7
2.0
-
0.5
1.5
1.3
0.7
-
4.3
3.8
3.1
3.2
0.9
0.0
1.4
0.9
3.4
1.3
10.7
2.7
0.0
4.6
0.9
0.9
0.8
recovery.
Relative percent difference between
duplicate spike
determi
nations.
Sample concentration below established method detection limit.
Spike concentration <10% of sample background concentration.
Not spiked.
Equivalent
200.7-52
Revision 4.4 May 1994
-------
TABLE 7: PRECISION AND RECOVERY DATA IN SOLID MATRICES (Cont.)
NBS 1645 RIVER SEDIMENT
SAMPLE LOW+
CONC SPIKE
AVERAGE
RECOVERY
ANALYTE mg/kg mg/kg R(%)
Ag
Al
As
B
Ba
Be
Ca
Cd
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
P
Pb
Sb
Se
Sn
Sr
Tl
V
Zn
S(R)
RPD
1.6
5160
62.8
31.9
54.8
0.72
28000
9.7
9.4
28500
109
84800
3.1
452
3.7
6360
728
17.9
1020
36.2
553
707
22.8
6.7
309
782
<4
20.1
1640
20
20
20
100
20
20
-
20
20
20
20
—
10
500
10
500
20
20
500
20
500
20
20
20
20
100
20
20
20
Standard deviation
Relative percent di
92
*
89
116
95
101
_
100
98
*
115
_
99
98
101
*
*
97
92
94
102
*
86
103
*
91
90
89
*
of percent
S(R)
0.4
*
14.4
7.1
6.1
0.4
_
1.1
3.8
*
8.5
_
4.3
4.1
2.0
*
*
12.5
2.6
5.9
1.4
*
2.3
14.3
*
12.3
0.0
5.4
*
HIGH
SPIKE
RPD mg/kg
1.0
8.4
9.7
13.5
2.8
1.0
_
0.0
4.8
0.4
0.0
_
7.7
2.0
0.7
1.8
3.5
18.5
0.0
4.0
0.9
0.8
0.0
27.1
1.0
3.0
0.0
5.8
1.8
100
100
100
400
100
100
. _
100
100
100
100
_
40
2000
40
2000
100
100
2000
100
2000
100
100
100
100
400
100
100
100
+ AVERAGE
RECOVERY
R(«)
96
*
97
95
98
103
_
101
98
*
102
96
106
108
93
97
98
97
100
100
103
88
98
101
96
95
98
*
S(R)
0.3
*
2.9
0.6
1.2
1.4
_
0.7
0.9
*
1.8
_
0.7
1.4
1.3
2.7
12.4
0.6
1.1
1.1
0.8
5.9
0.6
3.1
7.9
3.3
1.3
0.7
*
RPD
0.9
2.4
5.0
1.5
1.3
3.9
1.8
1.8
0.7
1.0
1.0
2.3
3.0
1.0
2.2
0.0
1.7
1.5
1.6
0,4
0.9
7.6
2.7
2.6
4.0
0.0
1.1
recovery.
fference between
duplicate spike
3 determin
ations.
Sample concentration below established method detection limit.
Spike concentration <10% of sample background concentration.
Not spiked.
Equivalent
200.7-53
Revision 4.4 May 1994
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TABLE 8: ICP-AES INSTRUMENTAL PRECISION AND ACCURACY FOR AQUEOUS SOLUTIONS8
Element
Al
Sb
As
Ba
Be
Cd
Ca
Cr
Co
Cu
Fe
Pb
Mg
Mn
Mo
Ni
K
Se
Na
Tl
V
Zn
Mean
Cone
(ma/L)
14.8
15.1
14.7
3.66
3.78
3.61
15.0
3.75
3.52
3.58
14.8
14.4
14.1
3.70
3.70
3.70
14.1
15.3
14.0
15.1
3.51
3.57
Nb
8
8
7
7
8
8
8
8
8
8
8
. 7
8
8
8
7
8
8
8
7
8
8
8 These performance values are
analyzed portions of the same
instruments."
b
c
N - Number
A*^/^nv»fi/^\# i
C.C.
RSD
(%) ('
6.3
7.7
6.4
3.1
5.8
7.0
7.4
8.2
5.9
5.6
5.9
5.9
6.5
4.3
6.9
5.7
6.6
7.5
4.2
8.5
6.6
8.3
Accuracy0
% of Nominal)
100
102
99
99
102
97
101
101
95
97
100
97
96
100
100
100
95
104
95
102
95
96
independent of sample preparation because the labs
solutions using sequential or simultaneous
of measurements for mean and
<« ovnv»QC carl a c
a n
Qvrontane n-f
relative standard deviation (RSD).
: the nominal value fnr each analvte in
the acidified, multi-element solutions.
200.7-54
Revision 4.4 May 1994
-------
TABLE 9: MULTILABORATORY ICP PRECISION AND ACCURACY DATA
Analyte
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Concentration
WJ/L
69-4792
77-1406
69-1887
9-377
3-1906
19-5189
9-1943
17-47170
13-1406
17-2340
8-1887
13-9359
42-4717
Total
X =
SR =
X =
SR =
X =
SR =
X =
SR =
X =
SR =
y _
SR =
X =
SR =
X =
SR =
X =
SR =
X =
SR =
X =
SR =
X =
SR =
X =
SR =
Recoverable
P./L
0.9380(C)
0.0481(X)
0.8908(C)
0.0682(X)
1.0175(C)
0.0643(X)
0.8380(C)
0.0826(X)
1.0177(C)
0.0445(X)
0.9676(C)
0.0743(X)
1.0137(C)
0.0332(X)
0.9658(C) +
0.0327(X) +
1.0049(C) -
0.0571(X) +
0.9278(C) -
0.0407(X) +
0.9647(C)
0.0406(X)
0.9830(C)
0.0790(X)
1.0056(C)
0.0448(X)
Digestion
+ 22.1
+ 18.8
+ 0.9
+ 2.5
+ 3.9
+ 10.3
+ 1.68
+ 3.54
- 0.55
- 0.10
+ 18.7
+ 21.1
- 0.65
+ 0.90
0.8
10.1
1.2
1.0
1.5
0.4
- 3.64
+ 0.96
+ 5.7
+ 11.5
+ 4.1
+ 3.5
- Regression equations abstracted from Reference 16.
X = Mean Recovery, /jg/L
C = True Value for the Concentration, /zg/L
SR = Single-analyst Standard Deviation, /ig/L
200.7-55
Revision 4.4 May 1994
-------
TABLE 9: HULTILABORATORY ICP PRECISION AND ACCURACY DATA* (Cont.)
Concentration
Analyte /jg/L
Magnesium
Manganese
Molybdenum
Nickel
Potassium
Selenium
Silicon
Silver
Sodium
Thallium
Vanadium
Zinc
34-13868
4-1887
17-1830
17-47170
347-14151
69-1415
189-9434
8-189
35-47170
79-1434
13-4698
7-7076
Total
X =
SR =
X =
SR =
X =
SR =
X =
SR =
X =
SR =
X =
SR =
X =
SR =
X =
SR =
X =
SR =
X =
SR =
X =
SR =
X =
SR =
Recoverable Digestion
It/I
0.9879(C) + 2.2
0.0268(X) + 8.1
0.9725(C) + 0.07
0.0400(X) + 0.82
0.9707(C) - 2.3
0.0529(X) + 2.1
0.9869(C) + 1.5
0.0393(X) + 2.2
0.9355(C) -183.1
0.0329(X) + 60.9
0.9737(C) - 1.0
0.0443(X) + 6.6
0.9737(C) - 60.8
0.2133(X) + 22.6
0.3987(C) + 8.25
0.1836(X) - 0.27
1.0526(C) + 26.7
0.0884(X) + 50.5
0.9238(C) + 5.5
-0.0106(X) + 48.0
0.9551(C) + 0.4
0.0472(X) + 0.5
0.9500(C) + 1.82
0.0153{X) + 7.78
- Regression equations abstracted from Reference 16.
X = Mean Recovery, jig/L
C = True Value for the Concentration, fig/L
SR » Single-analyst Standard Deviation, ng/L
200.7-56
Revision 4.4 May 1994
-------
Pb-Cu ICP-AES EMISSION PROFILE
32
30
28
26
24
22
20
18
16
14
Net Emision Intensity Counts (X10 )
12
475 525 575 625 675 725 775 825
Nebulizer Argon Flow Rate - mL/min
Figure 1
200.7-57 Revision 4.4 May 1994
-------
-------
METHOD 200.8
DETERMINATION OF TRACE ELEMENTS IN WATERS AND WASTES
BY INDUCTIVELY COUPLED PLASMA - MASS SPECTROMETRY
Revision 5.4
EMMC Version
S.E. Long (Technology Applications Inc.), T.D. Martin, and E.R. Martin -
Method 200.8, Revisions 4.2 and 4.3 (1990)
S.E. Long (Technology Applications Inc.) and T.D. Martin - Method 200.8
Revision 4.4 (1991)
J.T. Creed, C.A. Brockhoff, and T.D. Martin - Method 200.8, Revision 5.4
(1994)
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
200.8-1
-------
METHOD 200.8
DETERMINATION OF TRACE ELEMENTS IN WATERS AND WASTES
BY INDUCTIVELY COUPLED PLASMA - MASS SPECTROMETRY
1.0 SCOPE AND APPLICATION
1.1 This method provides procedures for determination of dissolved
elements in ground waters, surface waters and drinking water. It may
also be used for determination of total recoverable element
concentrations in these waters as well as wastewaters, sludges and
soils samples. This method is applicable to the following elements:
Analyte
Chemical Abstract Services
Registry Numbers (CASRN)
Aluminum
Antimony
Arsenic
Barium
Beryl 1 i urn
Cadmium
Chromium
Cobalt
Copper
Lead
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
Thallium
Thorium
Uranium
Vanadium
Zinc
(Al)
(Sb)
(As)
(Ba)
(Be)
(Cd)
(Cr)
(Co)
(Cu)
(Pb)
(Mn)
(Hg)
(Mo)
(Ni)
(Se)
(Ag)
(Tl)
(Th)
(U)
(V)
(Zn)
7429-90-5
7440-36-0
7440-38-2
7440-39-3
7440-41-7
7440-43-9
7440-47-3
7440-48-4
7440-50-8
7439-92-1
7439-96-5
7439-97-6
7439-98-7
7440-02-0
7782-49-2
7440-22-4
7440-28-0
7440-29-1
7440-61-1
7440-62-2
7440-66-6
Estimated instrument detection limits (IDLs) for these elements are
listed in Table 1. These are intended as a guide to instrumental
limits typical of a system optimized for multielement determinations
and employing commercial instrumentation and pneumatic nebulization
sample introduction. However, actual method detection limits (MDLs)
and linear working ranges will be dependent on the sample matrix,
instrumentation and selected operating conditions. Given in Table 7
are typical MDLs for both total recoverable determinations by "direct
analysis" and where sample digestion is employed.
200.8-2
Revision 5.4 May 1994
-------
1.2 For reference where this method is approved for use in compliance
monitoring programs [e.g., Clean Water Act (NPDES) or Safe Drinking
Water Act (SDWA)] consult both the appropriate sections of the Code of
Federal Regulation (40 CFR Part 136 Table IB for NPDES, and Part 141
§ 141.23 for drinking water), and the latest Federal Register
announcements.
1.3 Dissolved elements are determined after suitable filtration and acid
preservation. In order to reduce potential interferences, dissolved
solids should not exceed 0.2% (w/v) (Sect. 4.1.4).
1.4 With the exception of silver, where this method is approved for the
determination of certain metal and metalloid contaminants in drinking
water, samples may be analyzed directly by pneumatic nebulization
without acid digestion if the samples have been properly preserved
with acid and have turbidity of < 1 NTU at the time of analysis. This
total recoverable determination procedure is referred to as "direct
analysis".
1.5 For the determination of total recoverable analytes in aqueous and
solid samples a digestion/extraction is required prior to analysis
when the elements are not in solution (e.g., soils, sludges, sediments
and aqueous samples that may contain particulate and suspended
solids). Aqueous samples containing suspended or particulate material
> 1% (w/v) should be extracted as a solid type sample (Sect. 11.2.2).
1.6 The total recoverable sample digestion procedure given in this method
is not suitable for the determination of volatile organo-mercury
compounds. However, for "direct analysis" of drinking water
(turbidity < 1 NTU), the combined concentrations of inorganic and
organo-mercury in solution can be determined by "direct analysis"
pneumatic nebulization provided gold is added to both samples and
standards alike to eliminate memory interference effects.
1.7 Silver is only slightly soluble in the presence of chloride unless
there is a sufficient chloride concentration to form the soluble
chloride complex. Therefore, low recoveries of silver may occur in
samples, fortified sample matrices and even fortified blanks if
determined as a dissolved analyte or by "direct analysis" where the
sample has not been processed using the total recoverable mixed acid
digestion. For this reason it is recommended that samples be digested
prior to the determination of silver. The total recoverable sample
digestion procedure given in this method is suitable for the
determination of silver in aqueous samples containing concentrations
up to 0.1 mg/L. For the analysis of wastewater samples containing
higher concentrations of silver, succeeding smaller volume, well mixed
sample aliquots must be prepared until the analysis solution contains
< 0.1 mg/L silver. The extraction of solid samples containing
concentrations of silver > 50 mg/kg should be treated in a similar
manner.
1.8 The total recoverable sample digestion procedure given in this method
will solubilize and hold in solution only minimal concentrations of
200.8-3 Revision 5.4 May 1994
-------
barium in the presence of free sulfate. For the analysis of barium in
samples having varying and unknown concentrations of sulfate, analysis
should be completed as soon as possible after sample preparation.
1.9 This method should be used by analysts experienced in the use of
inductively coupled plasma mass spectrometry (ICP-MS), the interpreta-
tion of spectral and matrix interferences and procedures for their
correction. A minimum of six months experience with commercial
instrumentation is recommended.
1.10 Users of the method data should state the data-quality objectives
prior to analysis. Users of the method must document and have on file
the required initial demonstration performance data described in
Section 9.2 prior to using the method for analysis.
2.0 SUMMARY OF METHOD
2.1 An aliquot of a well mixed, homogeneous aqueous or solid sample is
accurately weighed or measured for sample processing. For total
recoverable analysis of a solid or an aqueous sample containing
undissolved material, analytes are first solubilized by gentle
refluxing with nitric and hydrochloric acids. After cooling, the
sample is made up to volume, is mixed and centrifuged or allowed to
settle overnight prior to analysis. For the determination of
dissolved analytes in a filtered aqueous sample aliquot, or for the
"direct analysis" total recoverable determination of analytes in
drinking water where sample turbidity is < 1 NTU, the sample is made
ready for analysis by the appropriate addition of nitric acid, and
then diluted to a predetermined volume and mixed before analysis.
2.2 The method describes the multi-element determination of trace elements
by ICP-MS. Sample material in solution is introduced by pneumatic
nebulization into a radiofrequency plasma where energy transfer
processes cause desolvation, atomization and ionization. The ions are
extracted from the plasma through a differentially pumped vacuum
interface and separated on the basis of their mass-to-charge ratio by
a quadrupole mass spectrometer having a minimum resolution capability
of 1 amu peak width at 5% peak height. The ions transmitted through
the quadrupole are detected by an electron multiplier or Faraday
detector and the ion information processed by a data handling system.
Interferences relating to the technique (Sect. 4) must be recognized
and corrected for. Such corrections must include compensation for
isobaric elemental interferences and interferences from polyatomic
ions derived from the plasma gas, reagents or sample matrix.
Instrumental drift as well as suppressions or enhancements of
instrument response caused by the sample matrix must be corrected for
by the use of internal standards.
3.0 DEFINITIONS
3.1 Calibration Blank - A volume of reagent water acidified with the same
acid matrix as in the calibration standards. The calibration blank is
a zero standard and is used to calibrate the ICP instrument (Sect.
7.6.1).
200.8-4 Revision 5.4 May 1994
-------
3.2 Calibration Standard (CAL) - A solution prepared from the dilution of
stock standard solutions. The CAL solutions are used to calibrate the
instrument response with respect to analyte concentration (Sect. 7.4).
3.3 Dissolved Analyte - The concentration of analyte in an aqueous sample
that will pass through a 0.45-0m membrane filter assembly prior to
sample acidification (Sect. 11.1).
3.4 Field Reagent Blank (FRB) - An aliquot of reagent water or other blank
matrix that is placed in a sample container in the laboratory and
treated as a sample in all respects, including shipment to the
sampling site, exposure to the sampling site conditions, storage
preservation, and all analytical procedures. The purpose of the FRB
is to determine if method analytes or other interferences are present
in the field environment (Sect 8.5).
3.5 Instrument Detection Limit (IDL) - The concentration equivalent to the
analyte signal which is equal to three times the standard deviation of
a series of ten replicate measurements of the calibration blank signal
at the selected analytical mass(es). (Table 1).
3.6 Internal Standard - Pure analyte(s) added to a sample, extract, or
standard solution in known amount(s) and used to measure the relative
responses of other method analytes that are components of the same
sample or solution. The internal standard must be an analyte that is
not a sample component (Sects. 7.5 & 9.4.5).
3'7
tnnth ih, , LD2) - Two ali«uots of the san)e
taken in the laboratory and analyzed separately with identical
procedures. Analyses of LD1 and LD2 indicates precision associated
with laboratory procedures, but not with sample collection
preservation, or storage procedures. i-nun,
3'8 ar F?r+;if1ed+!!la,nk: (tFB) - ^n a^^^ of LRB to which known
of the method analytes are added in the laboratory. The
thth +h63?Citly "ke-a Sample' and its purpose is to determine
whether the methodology is in control and whether the laboratory is
capable of making accurate and precise measurements (Sects. 7.9 &
y • o • L. ) •
3.9 Laboratory Fortified Sample Matrix (LFM) - An aliquot of an
environmental sample to which known quantities of the method analytes
are added in the laboratory. The LFM is analyzed exactly like a
sample, and its purpose is to determine whether the sample matrix
contributes bias to the analytical results. The background
concentrations of the analytes in the sample matrix must be determined
in a separate aliquot and the measured values in the LFM corrected for
background concentrations (Sect. 9.4).
3.10 [-^oratory Reagent ^ Blank (LRB) - An aliquot of reagent water or other
blank matrices that are treated exactly as a sample including exposure
IL^IL g]as?ware> equipment, solvents, reagents, and internal
standards that are used with other samples. The LRB is used to
200 • 8-5
Revision 5.4 May 1994
-------
determine if method analytes or other interferences are present in the
laboratory environment, reagents, or apparatus (Sects. 7.6.2 &9.3.1).
3.11 Linear Dynamic Range (LDR) - The concentration range over which the
instrument response to an analyte is linear (Sect. 9.2.2).
3.12 Method Detection Limit (MDL) - The minimum concentration of an analyte
that can be identified, measured, and reported with 99% confidence
that the analyte concentration is greater than zero (Sect. 9.2.4 and
Table 7).
3.13 Quality Control Sample (QCS) - A solution of method analytes of known
concentrations which is used to fortify an aliquot of LRB or sample
matrix. The QCS is obtained from a source external to the laboratory
and different from the source of calibration standards. It is used to
check either laboratory or instrument performance (Sects. 7.8 &
9.2.3).
3.14 Solid Sample - For the purpose of this method, a sample taken from
material classified as either soil, sediment or sludge.
3.15 Stock Standard Solution - A concentrated solution containing one or
more method analytes prepared in the laboratory using assayed
reference materials or purchased from a reputable commercial source
(Sect. 7.3).
3.16 Total Recoverable Analyte - The concentration of analyte determined
either by "direct analysis" of an unfiltered acid preserved drinking
water sample with turbidity of < 1 NTU (Sect. 11.2.1), or by analysis
of the solution extract of a solid sample or an unfiltered aqueous
sample following digestion by refluxing with hot dilute mineral
acid(s) as specified in the method (Sects. 11.2 & 11.3).
3.17 Tuning Solution - A solution which is used to determine acceptable
instrument performance prior to calibration and sample analyses (Sect.
7.7).
3.18 Water Sample - For the purpose of this method, a sample taken from one
of the following sources: drinking, surface, ground, storm runoff,
industrial or domestic wastewater.
4.0 INTERFERENCES
4.1 Several interference sources may cause inaccuracies in the
determination of trace elements by ICP-MS. These are:
4.1.1 Isobaric elemental interferences - Are caused by isotopes of
different elements which form singly or doubly charged ions of
the same nominal mass-to-charge ratio and which cannot be
resolved by the mass spectrometer in use. All elements deter-
mined by this method have, at a minimum, one isotope free of
isobaric elemental interference. Of the analytical isotopes
recommended for use with this method (Table 4), only molyb-
denum-98 (ruthenium) and selenium-82 (krypton) have isobaric
200.8-6 Revision 5.4 May 1994
-------
elemental interferences. If alternative analytical isotopes
having higher natural abundance are selected in order to
achieve greater sensitivity, an isobaric interference may
occur. All data obtained under such conditions must be
corrected by measuring the signal from another isotope of the
interfering element and subtracting the appropriate signal
ratio from the isotope of interest. A record of this
correction process should be included with the report of the
data. It should be noted that such corrections will only be as
accurate as the accuracy of the isotope ratio used in the
elemental equation for data calculations. Relevant isotope
ratios should be established prior to the application of any
corrections.
4.1.2 Abundance sensitivity - Is a property defining the degree to
which the wings of a mass peak contribute to adjacent masses.
The abundance sensitivity is affected by ion energy and quad-
rupole operating pressure. Wing overlap interferences may
result when a small ion peak is being measured adjacent to a
large one. The potential for these interferences should be
recognized and the spectrometer resolution adjusted to minimize
them.
4.1.3 Isobaric polyatomic ion interferences - Are caused by ions
consisting of more than one atom which have the same nominal
mass-to-charge ratio as the isotope of interest, and which
cannot be resolved by the mass spectrometer in use. These ions
are commonly formed in the plasma or interface system from
support gases or sample components. Most of the common
interferences have been identified3, and these are listed in
Table 2 together with the method elements affected. Such
interferences must be recognized, and when they cannot be
avoided by the selection of alternative analytical isotopes,
appropriate corrections must be made to the data. Equations
for the correction of data should be established at the time of
the analytical run sequence as the polyatomic ion interferences
will be highly dependent on the sample matrix and chosen
instrument conditions. In particular, the common 82Kr
interference that affects the determination of both arsenic and
selenium, can be greatly reduced with the use of high purity
krypton free argon.
4.1.4 Physical interferences - Are associated with the physical
processes which govern the transport of sample into the plasma,
sample conversion processes in the plasma, and the
transmission of ions through the plasma-mass spectrometer
interface. These interferences may result in differences bet-
ween instrument responses for the sample and the calibration
standards. Physical interferences may occur in the transfer of
solution to the nebulizer (e.g., viscosity effects), at the
point of aerosol formation and transport to the plasma (e.g.,'
surface tension), or during excitation and ionization processes
within the plasma itself. High levels of dissolved solids in
the sample may contribute deposits of material on the
200.8-7 Revision 5.4 May 1994
-------
extraction and/or skimmer cones reducing the effective diameter
of the orifices and therefore ion transmission. Dissolved
solids levels not exceeding 0.2% (w/v) have been recommended
to reduce such effects. Internal standardization may be
effectively used to compensate for many physical interference
effects.4 Internal standards ideally should have similar
analytical behavior to the elements being determined.
4.1.5 Memory interferences - Result when isotopes of elements in a
previous sample contribute to the signals measured in a new
sample. Memory effects can result from sample deposition on
the sampler and skimmer cones, and from the buildup of sample
material in the plasma torch and spray chamber. The site where
these effects occur is dependent on the element and can be
minimized by flushing the system with a rinse blank between
samples (Sect. 7.6.3). The possibility of memory interferences
should be recognized within an analytical run and suitable
rinse times should be used to reduce them. The rinse times
necessary for a particular element should be estimated prior to
analysis. This may be achieved by aspirating a standard
containing elements corresponding to ten times the upper end of
the linear range for a normal sample analysis period, followed
by analysis of the rinse blank at designated intervals. The
length of time required to reduce analyte signals to within a
factor of ten of the method detection limit, should be noted.
Memory interferences may also be assessed within an analytical
run by using a minimum of three replicate integrations for data
acquisition. If the integrated signal values drop
consecutively, the analyst should be alerted to the possibility
of a memory effect, and should examine the analyte con-
centration in the previous sample to identify if this was high.
If a memory interference is suspected, the sample should be
reanalyzed after a long rinse period. In the determination of
mercury, which suffers from severe memory effects, the addition
of 100 /jg/L gold will effectively rinse 5 /jg/L mercury in
approximately 2 minutes. Higher concentrations will require a
longer rinse time.
5.0 SAFETY
5.1 The toxicity or carcinogenicity of reagents used in this method have
not been fully established. Each chemical should be regarded as a
potential health hazard and exposure to these compounds should be as
low as reasonably achievable. Each laboratory is responsible for
maintaining a current awareness file of OSHA regulations regarding the
safe handling of the chemicals specified in this method. ' A
reference file of material data handling sheets should also be avail-
able to all personnel involved in the chemical analysis.
Specifically, concentrated nitric and hydrochloric acids present
various hazards and are moderately toxic and extremely irritating to
skin and mucus membranes. Use these reagents in a fume hood whenever
200.8-8 Revision 5.4 May 1994
-------
possible and if eye or skin contact occurs, flush with large volumes
of water. Always wear safety glasses or a shield for eye protection,
protective clothing and observe proper mixing when working with these
reagents.
5.2 The acidification of samples containing reactive materials may result
!n. ™J: release of toxic gases, such as cyanides or sulfides.
Acidification of samples should be done in a fume hood.
5.3 All personnel handling environmental samples known to contain or to
have been in contact with human waste should be immunized aqainst
known disease causative agents.
5.4 Analytical plasma sources emit radiofrequency radiation in addition to
intense UV radiation. Suitable precautions should be taken to protect
personnel from such hazards. The inductively coupled plasma should
only be viewed with proper eye protection from UV emissions.
5.5 It is the responsibility of the user of this method to comply with
relevant disposal and waste regulations. For guidance see Sections
14.0 and 15.0.
6.0 EQUIPMENT AND SUPPLIES
6.1 Inductively coupled plasma mass spectrometer:
6.1.1 Instrument capable of scanning the mass range 5-250 amu with a
minimum resolution capability of 1 amu peak width at 5% peak
height. Instrument may be fitted with a conventional or ex-
tended dynamic range detection system.
NOTE: If an electron multiplier detector is being used,
precautions should be taken, where necessary to
prevent exposure to high ion flux. Otherwise changes
in instrument response or damage to the multiplier may
result.
6.1.2 Radio-frequency generator compliant with FCC regulations.
6.1.3 Argon gas supply - High purity grade (99.99%). When analyses
are conducted frequently, liquid argon is more economical and
requires less frequent replacement of tanks than compressed
argon in conventional cylinders (Sect. 4.1.3).
6.1.4 A variable-speed peristaltic pump is required for solution
delivery to the nebulizer.
6.1.5 A mass-flow controller on the nebulizer gas supply is required
A water-cooled spray chamber may be of benefit in reducing some
types of interferences (e.g., from polyatomic oxide species).
6.1.6 If an electron multiplier detector is being used, precautions
should be taken, where necessary, to prevent exposure to high
ion flux. Otherwise changes in instrument response or damage
to the multiplier may result. Samples having high
200.8-9 Revision 5.4 May 1994
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concentrations of elements beyond the linear range of the
instrument and with isotopes falling within scanning windows
should be diluted prior to analysis.
6.2 Analytical balance, with capability to measure to 0.1 mg, for use in
weighing solids, for preparing standards, and for determining
dissolved solids in digests or extracts.
6.3 A temperature adjustable hot plate capable of maintaining a
temperature of 95°C.
6.4 (optional) A temperature adjustable block digester capable of
maintaining a temperature of 95°C and equipped with 250-mL constricted
digestion tubes.
6.5 (optional) A steel cabinet centrifuge with guard bowl, electric timer
and brake.
6.6 A gravity convection drying oven with thermostat!c control capable of
maintaining 105°C ± 5°C.
6.7 (optional) An air displacement pipetter capable of delivering volumes
ranging from 0.1 to 2500 /*L with an assortment of high quality
disposable pipet tips.
6.8 Mortar and pestle, ceramic or nonmetallic material.
6.9 Polypropylene sieve, 5-mesh (4 mm opening).
6.10 Labware - For determination of trace levels of elements, contamination
and loss are of prime consideration. Potential contamination sources
include improperly cleaned laboratory apparatus and general
contamination within the laboratory environment from dust, etc. A
clean laboratory work area designated for trace element sample
handling must be used. Sample containers can introduce positive and
negative errors in the determination of trace elements by (1)
contributing contaminants through surface desorption or leaching, (2)
depleting element concentrations through adsorption processes. All
reusable labware (glass, quartz, polyethylene, PTFE, FEP, etc.) should
be sufficiently clean for the task objectives. Several procedures
found to provide clean labware include soaking overnight and
thoroughly washing with laboratory-grade detergent and water, rinsing
with tap water, and soaking for four hours or more in 20% (V/V) nitric
acid or a mixture of dilute nitric and hydrochloric acid (1+2+9),
followed by rinsing with reagent grade water and storing clean.
NOTE: Chromic acid must not be used for cleaning glassware.
6.10.1 Glassware - Volumetric flasks, graduated cylinders, funnels and
centrifuge tubes (glass and/or metal free plastic).
6.10.2 Assorted calibrated pipettes.
200.8-10 Revision 5.4 May 1994
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6.10.3 Conical Phillips beakers (Corning 1080-250 or equivalent) 250-
mL with 50-mm watch glasses.
6.10.4 Griffin beakers, 250-mL with 75-mm watch glasses and (optional)
75-mm ribbed watch glasses.
6.10.5 (optional) PTFE and/or quartz beakers, 250-mL with PTFE covers.
6.10.6 Evaporating dishes or high-form crucibles, porcelain, 100 mL
capacity.
6.10.7 Narrow-mouth storage bottles, FEP (fluorinated ethylene
propylene) with ETFE (ethylene tetrafluorethylene) screw
closure, 125-mL to 250-mL capacities.
6.10.8 One-piece stem FEP wash bottle with screw closure, 125-mL
capacity.
7.0 REAGENTS AND STANDARDS
7.1 Reagents may contain elemental impurities that might affect the
integrity of analytical data. Owing to the high sensitivity of ICP-
MS, high-purity reagents should be used whenever possible. All acids
used for this method must be of ultra high-purity grade. Suitable
acids are available from a number of manufacturers or may be prepared
by sub-boiling distillation. Nitric acid is preferred for ICP-MS in
order to minimize polyatomic ion interferences. Several polyatomic ion
interferences result when hydrochloric acid is used (Table 2)
however, it should be noted that hydrochloric acid is required to
maintain stability in solutions containing antimony and silver. When
hydrochloric acid is used, corrections for the chloride polyatomic ion
interferences must be applied to all data.
7.1.1 Nitric acid, concentrated (sp.gr. 1.41).
7.1.2 Nitric acid (1+1) - Add 500 mL cone, nitric acid to 400 mL of
regent grade water and dilute to 1 L.
7.1.3 Nitric acid (1+9) - Add 100 mL cone, nitric acid to 400 mL of
reagent grade water and dilute to 1 L.
7.1.4 Hydrochloric acid, concentrated (sp.gr. 1.19).
7.1.5 Hydrochloric acid (1+1) - Add 500 mL cone, hydrochloric acid to
400 mL of reagent grade water and dilute to 1 L.
7.1.6 Hydrochloric acid (1+4) - Add 200 mL cone, hydrochloric acid to
400 mL of reagent grade water and dilute to 1 L.
7.1.7 Ammonium hydroxide, concentrated (sp.gr. 0.902).
7.1.8 Tartaric acid (CASRN 87-69-4).
200.8-11 Revision 5.4 May 1994
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7.2 Reagent water - All references to reagent grade water in this method
refer to ASTM type I water (ASTM D1193). Suitable water may be
prepared by passing distilled water through a mixed bed of anion and
cation exchange resins.
7.3 Standard Stock Solutions - Stock standards may be purchased from a
reputable commercial source or prepared from ultra high-purity grade
chemicals or metals (99.99 - 99.999% pure). All salts should be dried
for 1 h at 105°C, unless otherwise specified. Stock solutions should
be stored in FEP bottles. Replace stock standards when succeeding
dilutions for preparation of the multielement stock standards can not
be verified.
CAUTION: Many metal salts are extremely toxic if inhaled or
swallowed. Wash hands thoroughly after handling.
The following procedures may be used for preparing standard stock
solutions:
NOTE: Some metals, particularly those which form surface oxides
require cleaning prior to being weighed. This may be achieved
by pickling the surface of the metal in acid. An amount in
excess of the desired weight should be pickled repeatedly,
rinsed with water, dried and weighed until the desired weight
is achieved.
7.3.1 Aluminum solution, stock 1 ml = 1000 ^g Al: Pickle aluminum
metal in warm (1+1) HC1 to an exact weight of 0.100 g. Dissolve
in 10 ml cone. HC1 and 2 ml cone, nitric acid, heating to
effect solution. Continue heating until volume is reduced to
4 ml. Cool and add 4 ml reagent grade water. Heat until the
volume is reduced to 2 ml. Cool and dilute to 100 ml with
reagent grade water.
7.3.2 Antimony solution, stock 1 ml = 1000 pg Sb: Dissolve 0.100 g
antimony powder in 2 ml (1+1) nitric acid and 0.5 ml cone.
hydrochloric acid, heating to effect solution. Cool, add 20 ml
reagent grade water and 0.15 g tartaric acid. Warm the
solution to dissolve the white precipitate. Cool and dilute to
100 ml with reagent grade water.
7.3.3 Arsenic solution, stock 1 ml = 1000 jug As: Dissolve 0.1320 g
As203 in a mixture of 50 ml reagent grade water and 1 ml cone.
ammonium hydroxide. Heat gently,to dissolve. Cool and acidify
the solution with 2 mL cone, nitric acid. Dilute to 100 ml
with reagent grade water.
7.3.4 Barium solution, stock 1 ml = 1000 jug Ba: Dissolve 0.1437 g
BaCCL in a solution mixture of 10 ml reagent grade water and
2 ml cone, nitric acid. Heat and stir to effect solution and
degassing. Dilute to 100 ml with reagent grade water.
200.8-12 Revision 5.4 May 1994
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7.3.5 Beryllium solution, stock 1 ml = 1000 /zg Be: Dissolve 1 965 q
BeS04.4H 0 (DO NOT DRY) in 50 ml reagent grade water. Add 1 ml
cone, nitric acid. Dilute to 100 ml with reagent grade water.
7.3.6 Bismuth solution, stock 1 ml = 1000 jug Bi : Dissolve 0.1115 g
Bip03 in 5 ml cone, nitric acid. Heat to effect solution. Cool
and dilute to 100 ml with reagent grade water.
7.3.7 Cadmium solution, stock 1 mL = 1000 jug Cd: Pickle cadmium metal
in (1+9) nitric acid to an exact weight of 0.100 g. Dissolve in
5 mL (1+1) nitric acid, heating to effect solution. Cool and
dilute to 100 ml with reagent grade water.
7.3.8 Chromium solution, stock 1 ml = 1000 jug Cr: Dissolve 0.1923 g
CrO, in a solution mixture of 10 ml reagent grade water and
1 ml cone, nitric acid. Dilute to 100 ml with reagent grade
7.3.9 Cobalt solution, stock 1 ml = 1000 jug Co: Pickle cobalt metal
in (1+9) nitric acid to an exact weight of 0.100 g. Dissolve in
5-n +(1J"1)1"1tric acid' Bating to effect solution. Cool and
dilute to 100 mL with reagent grade water.
7.3.10 Copper solution, stock 1 ml = 1000 jug Cu: Pickle copper metal
in (1+9) nitric acid to an exact weight of 0.100 g. Dissolve in
5 mL (1+1) nitric acid, heating to effect solution. Cool and
dilute to 100 ml with reagent grade water.
7.3.11 Gold solution, stock 1 ml = 1000 //g Au: Dissolve 0.100 g high
purity (99.9999%) Au shot in 10 ml of hot cone, nitric acid by
dropwise addition of 5 ml cone. HC1 and then reflux to expel
oxides of nitrogen and chlorine. Cool and dilute to 100 ml
with reagent grade water.
7.3.12 Indium solution, stock 1 mL = 1000 jug In: Pickle indium metal
in (1+1) nitric acid to an exact weight of 0.100 g. Dissolve in
10 mL (1+1 nitric acid, heating to effect solution. Cool and
dilute to 100 mL with reagent grade water.
7.3.13 Lead solution, stock 1 mL = 1000 jug Pb: Dissolve 0.1599 g PbNO
in 5 mL (1+1) nitric acid. Dilute to 100 mL with reagent gradl
water.
7.3.14 Magnesium solution, stock 1 mL = 1000 jug Mg: Dissolve 0 1658 g
MgO in 10 mL (1+1) nitric acid, heating to effect soiution.
cool and dilute to 100 mL with reagent grade water.
7.3.15 Manganese solution, stock 1 mL = 1000 /ug Mn: Pickle manganese
flake in (1+9) nitric acid to an exact weight of 0.100 q
Dissolve in 5 mL (1+1) nitric acid, heating to effect solution!
Cool and dilute to 100 mL with reagent grade water
200.8-13 Revision 5.4 May 1994
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7.3.16 Mercury solution, stock, 1 ml = 1000 /tg Hg: DO NOT DRY.
CAUTION: highly toxic element. Dissolve 0.1354 g HgCl2 in
reagent water. Add 5.0 ml concentrated HN03 and dilute to 100
ml with reagent water.
7.3.17 Molybdenum solution, stock 1 ml = 1000 jug Mo: Dissolve 0.1500
g MoO, in a solution mixture of 10 ml reagent grade water and
1 ml cone, ammonium hydroxide., heating to effect solution.
Cool and dilute to 100 ml with reagent grade water.
7.3.18 Nickel solution, stock 1 ml = 1000 jug Ni: Dissolve 0.100 g
nickel powder in 5 ml cone, nitric acid, heating to effect
solution. Cool and dilute to 100 ml with reagent grade water.
7.3.19 Scandium solution, stock 1 ml = 1000 jug Sc: Dissolve 0.1534 g
Sc20, in 5 ml (1+1) nitric acid, heating to effect solution.
Cool and dilute to 100 ml with reagent grade water.
7.3.20 Selenium solution, stock 1 ml - 1000 jug Se: Dissolve 0.1405 g
SeOo in 20 ml ASTM type I water. Dilute to 100 ml with reagent
grade water.
7.3.21 Silver solution, stock 1 ml = 1000 jug Ag: Dissolve 0.100 g
silver metal in 5 ml (1+1) nitric acid, heating to effect
solution. Cool and dilute to 100 ml with reagent grade water.
Store in dark container.
7.3.22 Terbium solution, stock 1 ml = 1000 jug Tb: Dissolve 0.1176 g
Tb407 in 5 ml cone, nitric acid, heating to effect solution.
Cool and dilute to 100 ml with reagent grade water.
7.3.23 Thallium solution, stock 1 ml = 1000 pg Tl: Dissolve 0.1303 g
T1NO, in a solution mixture of 10 ml reagent grade water and 1
ml cone, nitric acid. Dilute to 100 ml with reagent grade
water.
7.3.24 Thorium solution, stock 1 ml = 1000 jug Th: Dissolve 0.2380 g
Th(N03)4.4H20 (DO NOT DRY) in 20 ml reagent grade water.
Dilute to 100 ml with reagent grade water.
7.3.25 Uranium solution, stock 1 ml = 1000 /ug U: Dissolve 0.2110 g
U02(NO,)2.6H20 (DO NOT DRY) in 20 ml reagent grade water and
dilute to 100 ml with reagent grade water.
7.3.26 Vanadium solution, stock 1 ml = 1000 jug V: Pickle vanadium
metal in (1+9) nitric acid to an exact weight of 0.100 g.
Dissolve in 5 ml (1+1) nitric acid, heating to effect solution.
Cool and dilute to 100 ml with reagent grade water.
7.3.27 Yttrium solution, stock 1 ml = 1000 ug Y: Dissolve 0.1270 g
Y,0, in 5 ml (1+1) nitric acid, heating to effect solution.
Cool and dilute to 100 ml with reagent grade water.
200.8-14 Revision 5.4 May 1994
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7.3.28 Zinc solution, stock 1 ml = 1000 /ig Zn: Pickle zinc metal in
(1+9) nitric acid to an exact weight of 0.100 g. Dissolve in
5 ml (1+1) nitric acid, heating to effect solution. Cool and
dilute to 100 ml_ with reagent grade water.
7.4 Multielement Stock Standard Solutions - Care must be taken in the
preparation of multielement stock standards that the elements are
compatible and stable. Originating element stocks should be checked
for the presence of impurities which might influence the accuracy of
the standard. Freshly prepared standards should be transferred to
acid cleaned, not previously used FEP fluorocarbon bottles for storage
and monitored periodically for stability. The following combinations
of elements are suggested:
Standard Solution A Standard Solution B
Aluminum Mercury Barium
Antimony Molybdenum Silver
Arsenic Nickel
Beryllium Selenium
Cadmium Thallium
Chromium Thorium
Cobalt Uranium
Copper Vanadium
Lead Zinc
Manganese
Except for selenium and mercury, multielement stock standard solutions
A and B (1 mL = 10 /zg) may be prepared by diluting 1.0 ml of each
single element stock standard in the combination list to 100 ml with
reagent water containing 1% (v/v) nitric acid. For mercury and
selenium in solution A, aliquots of 0.05 ml and 5.0 ml of the
respective stock standards should be diluted to the specified 100 ml
(1 ml = 0.5 /jg Hg and 50 /jg Se). Replace the multielement stock
standards when succeeding dilutions for preparation of the calibration
standards cannot be verified with the quality control sample.
7.4.1 Preparation of calibration standards - fresh multielement
calibration standards should be prepared every two weeks or as
needed. Dilute each of the stock multielement standard solu-
tions A and B to levels appropriate to the operating range of
the instrument using reagent water containing 1% (v/v) nitric
acid. The element concentrations in the standards should be
sufficiently high to produce good measurement precision and to
accurately define the slope of the response curve. Depending
on the sensitivity of the instrument, concentrations ranging
from 10 ng/l to 200 jug/L are suggested, except mercury, which
should be limited to < 5 /zg/L. It should be noted the selenium
concentration is always a factor of 5 > the other analytes. If
the direct addition procedure is being used (Method A, Sect.
10.3), add internal standards (Sect. 7.5) to the calibration
standards and store in FEP bottles. Calibration standards
200.8-15 Revision 5.4 May 1994
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should be verified initially using a quality control sample
(Sect. 7.8).
7.5 Internal Standards Stock Solution - 1 ml = 100 jug. Dilute 10 ml of
scandium, yttrium, indium, terbium and bismuth stock standards (Sect.
7.3) to 100 ml with reagent water, and store in a FEP bottle. Use
this solution concentrate for addition to blanks, calibration stan-
dards and samples, or dilute by an appropriate amount using 1% (v/v)
nitric acid, if the internal standards are being added by peristaltic
pump (Method B, Sect. 10.3).
NOTE: If mercury is to be determined by the "direct analysis"
procedure, add an aliquot of the gold stock standard (Sect.
7.3.11) to the internal standard solution sufficient to provide
a concentration of 100 jtg/L in final the dilution of all
blanks, calibration standards, and samples.
7.6 Blanks - Three types of blanks are required for this method. A
calibration blank is used to establish the analytical calibration
curve, the laboratory reagent blank is used to assess possible
contamination from the sample preparation procedure and to assess
spectral background and the rinse blank is used to flush the
instrument between samples in order to reduce memory interferences.
7.6.1 Calibration blank - Consists of 1% (v/v) nitric acid in reagent
grade water. If the direct addition procedure (Method A, Sect.
10.3) is being used, add internal standards.
7.6.2 Laboratory reagent blank (LRB) - Must contain all the reagents
in the same volumes as used in processing the samples. The LRB
must be carried through the same entire preparation scheme as
the samples including digestion, when applicable. If the
direct addition procedure (Method A, Sect. 10.3) is being used,
add internal standards to the solution after preparation is
complete.
7.6.3 Rinse blank - Consists of 2% (v/v) nitric acid in reagent grade
water.
NOTE: If mercury is to be determined by the "direct analysis"
procedure, add gold (Sect. 7.3.11) to the rinse blank
to a concentration of 100 /jg/L.
7.7 Tuning Solution - This solution is used for instrument tuning and mass
calibration prior to analysis. The solution is prepared by mixing
beryllium, magnesium, cobalt, indium and lead stock solutions (Sect.
7.3) in 1% (v/v) nitric acid to produce a concentration of 100 jug/L of
each element. Internal standards are not added to this solution.
(Depending on the sensitivity of the instrument, this solution may
need to be diluted 10 fold.)
7.8 Quality Control Sample (QCS) - The QCS should be obtained from a
source outside the laboratory. The concentration of the QCS solution
200.8-16 Revision 5.4 May 1994
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analyzed will depend on the sensitivity of the instrument. To prepare
the QCS dilute an appropriate aliquot of analytes to a concentration
< 100 fj.g/1 in 1% (v/v) nitric acid. Because of lower sensitivity,
selenium may be diluted to a concentration of < 500 ng/l, however, in
all cases, mercury should be limited to a concentration of < 5 #g/L.
If the direct addition procedure (Method A, Sect. 10.3) is being used,
add internal standards after dilution, mix and store in a FEP bottle.
The QCS should be analyzed as needed to meet data-quality needs and a
fresh solution should be prepared quarterly or more frequently as
needed.
7.9 Laboratory Fortified Blank (LFB) - To an aliquot of LRB, add aliquots
from multielement stock standards A and B (Sect. 7.4) to prepared the
LFB. Depending on the sensitivity of the instrument, the fortified
concentration used should range from 40 /tg/L to 100 /-tg/L for each
analyte, except selenium and mercury. For selenium the concentration
should range from 200 /jg/L to 500 jttg/L, while the concentration range
mercury should be limited to 2 /ig/L to 5 fig/I. The LFB must be
carried through the same entire preparation scheme as the samples
including sample digestion, when applicable. If the direct addition
procedure (Method A, Sect. 10.3) is being used, add internal standards
to this solution after preparation has been completed.
8.0 SAMPLE COLLECTION. PRESERVATION. AND STORAGE
8.1 Prior to the collection of an aqueous sample, consideration should be
given to the type of data required, (i.e., dissolved or total
recoverable), so that appropriate preservation and pretreatment steps
can be taken. The pH of all aqueous samples must be tested
immediately prior to aliquoting for processing or "direct analysis" to
ensure the sample has been properly preserved. If properly acid
preserved, the sample can be held up to 6 months before analysis.
8.2 For the determination of dissolved elements, the sample must be
filtered through a 0.45-Aun pore diameter membrane filter at the time
of collection or as soon thereafter as practically possible. Use a
portion of the sample to rinse the filter flask, discard this portion
and collect the required volume of filtrate. Acidify the filtrate
with (1+1) nitric acid immediately following filtration to pH < 2.
8.3 For the determination of total recoverable elements in aqueous
samples, samples are not filtered, but acidified with (1+1) nitric
acid to pH < 2 (normally, 3 mL of (1+1) acid per liter of sample is
sufficient for most ambient and drinking water samples). Preservation
may be done at the time of collection, however, to avoid the hazards
of strong acids in the field, transport restrictions, and possible
contamination it is recommended that the samples be returned to the
laboratory within two weeks of collection and acid preserved upon
receipt in the laboratory. Following acidification, the sample should
be mixed, held for sixteen hours, and then verified to be pH < 2 just
prior withdrawing an aliquot for processing or "direct analysis". If
for some reason such as high alkalinity the sample pH is verified to
200.8-17 Revision 5.4 May 1994
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be > 2, more acid must be added and the sample held for sixteen hours
until verified to be pH < 2. See Section 8.1.
NOTE: When the nature of the sample is either unknown or known to be
hazardous, acidification should be done in a fume hood. See
Section 5.2.
8.4 Solid samples require no preservation prior to analysis other than
storage at 4°C. There is no established holding time limitation for
solid samples.
8.5 For aqueous samples, a field blank should be prepared and analyzed as
required by the data user. Use the same container and acid as used in
sample collection.
9.0 QUALITY CONTROL
9.1 Each laboratory using this method is required to operate a formal
quality control (QC) program. The minimum requirements of this
program consist of an initial demonstration of laboratory capability,
and the periodic analysis of laboratory reagent blanks, fortified
blanks and calibration solutions as a continuing check on performance.
The laboratory is required to maintain performance records that define
the quality of the data thus generated.
9.2 Initial Demonstration of Performance (mandatory)
9.2.1 The initial demonstration of performance is used to
characterize instrument performance (determination of linear
calibration ranges and analysis of quality control samples) and
laboratory performance (determination of method detection
limits) prior to analyses conducted by this method.
9.2.2 Linear calibration ranges - Linear calibration ranges are
primarily detector limited. The upper limit of the linear
calibration range should be established for each analyte by
determining the signal responses from a minimum of three
different concentration standards, one of which is close to the
upper limit of the linear range. Care should be taken to avoid
potential damage to the detector during this process. The
linear calibration range which may be used for the analysis of
samples should be judged by the analyst from the resulting
data. The upper LDR limit should be an observed signal no more
than 10% below the level extrapolated from lower standards.
Determined sample analyte concentrations that are greater than
90% of the determined upper LDR limit must be diluted and
reanalyzed. The LDRs should be verified whenever, in the
judgement of the analyst, a change in analytical performance
caused by either a change in instrument hardware or operating
conditions would dictate they be redetermined.
9.2.3 Quality control sample (QCS) - When beginning the use of this
method, on a quarterly basis or as required to meet data-
200.8-18 Revision 5.4 May 1994
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9.2.4
quality needs, verify the calibration standards and acceptable
instrument performance with the preparation and analyses of a
QCS (Sect. 7.8). To verify the calibration standards the
determined mean concentration from 3 analyses of the QCS must
be within ± 10% of the stated QCS value. If the QCS is used
for determining acceptable on-going instrument performance,
analysis of the QCS prepared to a concentration of 100 /*g/L
must be within ± 10% of the stated value or within the
acceptance limits listed in Table 8, whichever is the greater.
(If the QCS is not within the required limits, an immediate
second analysis of the QCS is recommended to confirm
unacceptable performance.) If the calibration standards and/or
acceptable instrument performance cannot be verified, the
source of the problem must be identified and corrected before
either proceeding on with the initial determination of method
detection limits or continuing with on-going analyses.
Method detection limits (MDL) should be established for all
analytes, using reagent water (blank) fortified at a
concentration of two to five times the estimated detection
limit. To determine MDL values, take seven replicate aliquots
of the fortified reagent water and process through the entire
analytical method. Perform all calculations defined in the
method and report the concentration values in the appropriate
units. Calculate the MDL as follows:
MDL = (t) x (S)
where: t = Student's t value for a 99% confidence level and
a standard deviation estimate with n-1 degrees of
freedom [t = 3.14 for seven replicates].
S = standard deviation of the replicate analyses.
Note: If additional confirmation is desired, reanalyze the
seven replicate aliquots on two more nonconsecutive
days and again calculate the MDL values for each day.
An average of the three MDL values for each analyte
may provide for a more appropriate MDL estimate. If
the relative standard deviation (RSD) from the analyses
of the seven aliquots is < 10%, the concentration used
to determine the analyte MDL may have been
inappropriately high for the determination. If so,
this could result in the calculation of an
unrealistically low MDL. Concurrently, determination
of MDL in reagent water represents a best case
situation and does not reflect possible matrix effects
of real world samples. However, successful analyses of
LFMs (Sect. 9.4) can give confidence to the MDL value
determined in reagent water. Typical single laboratory
MDL values using this method are given in Table 7.
The MDLs must be sufficient to detect analytes at the required
levels according to compliance monitoring regulation (Sect.
200.8-19
Revision 5.4 May 1994
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1.2). MDLs should be determined annually, when a new operator
begins work or whenever, in the judgement of the analyst, a
change in analytical performance caused by either a change in
instrument hardware or operating conditions would dictate they
be redetermined.
9.3 Assessing Laboratory Performance (mandatory)
9.3.1 Laboratory reagent blank (LRB) - The laboratory must analyze at
least one LRB (Sect. 7.6.2) with each batch of 20 or fewer of
samples of the same matrix. LRB data are used to assess
contamination from the laboratory environment and to
characterize spectral background from the reagents used in
sample processing. LRB values that exceed the MDL indicate
laboratory or reagent contamination should be suspected. When
LRB values constitute 10% or more of the analyte level
determined for a sample or is 2.2 times the analyte MDL
whichever is greater, fresh aliquots of the samples must be
prepared and analyzed again for the affected analytes after the
source of contamination has been corrected and acceptable LRB
values have been obtained.
9.3.2 Laboratory fortified blank (LFB) - The laboratory must analyze
at least one LFB (Sect. 7.9) with each batch of samples.
Calculate accuracy as percent recovery using the following
equation:
LFB - LRB
R =
x 100
where: R = percent recovery.
LFB = laboratory fortified blank.
LRB = laboratory reagent blank.
s = concentration equivalent of analyte
added to fortify the LRB solution.
If the recovery of any analyte falls outside the required
control limits of 85-115%, that analyte is judged out of
control, and the source of the problem should be identified and
resolved before continuing analyses.
9.3.3 The laboratory must use LFB analyses data to assess laboratory
performance against the required control limits of 85-115%
(Sect.9.3.2). When sufficient internal performance data become
available (usually a minimum of twenty to thirty analyses),
optional control limits can be developed from the mean percent
recovery (x) and the standard deviation (S) of the mean percent
recovery. These data can be used to establish the upper and
lower control limits as follows:
UPPER CONTROL LIMIT = x + 3S
LOWER CONTROL LIMIT = x - 3S
200.8-20
Revision 5.4 May 1994
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The optional control limits must be equal to or better than the
required control limits of 85-115%. After each five to ten new
recovery measurements, new control limits can be calculated
using only the most recent twenty to thirty data points. Also,
the standard deviation (S) data should be used to establish an
on-going precision statement for the level of concentrations
included in the LFB. These data must be kept on file and be
available for review.
9.3.4 Instrument performance - For all determinations the laboratory
must check instrument performance and verify that the
instrument is properly calibrated on a continuing basis. To
verify calibration run the calibration blank and calibration
standards as surrogate samples immediately following each
calibration routine, after every ten analyses and at the end of
the sample run. The results of the analyses of the standards
will indicate whether the calibration remains valid. The
analysis of all analytes within the standard solutions must be
within ± 10% of calibration. If the calibration cannot be
verified within the specified limits, the instrument must be
recalibrated. (The instrument responses from the calibration
check may be used for recalibration purposes, however, it must
be verified before continuing sample analysis.) If the
continuing calibration check is not confirmed within ± 15%, the
previous ten samples must be reanalyzed after recalibration.
If the sample matrix is responsible for the calibration drift,
it is recommended that the previous ten samples are reanalyzed
in groups of five between calibration checks to prevent a
similar drift situation from occurring.
9.4 Assessing Analyte Recovery and Data Quality
9.4.1 Sample homogeneity and the chemical nature of the sample matrix
can affect analyte recovery and the quality of the data.
Taking separate aliquots from the sample for replicate and
fortified analyses can in some cases assess the effect. Unless
otherwise specified by the data user, laboratory or program,
the following laboratory fortified matrix (LFM) procedure (Sect
9.4.2) is required.
9.4.2 The laboratory must add a known amount of analyte to a minimum
of 10% of the routine samples. In each case the LFM aliquot
must be a duplicate of the aliquot used for sample analysis and
for total recoverable determinations added prior to sample
preparation. For water samples, the added analyte con-
centration must be the same as that used in the laboratory
fortified blank (Sect. 7.9). For solid samples, the
concentration added should be 100 mg/kg equivalent (200 jiig/L
in the analysis solution) except silver which should be limited
to 50 mg/kg (Sect 1.8). Over time, samples from all routine
sample sources should be fortified.
200.8-21 Revision 5.4 May 1994
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9.4.3 Calculate the percent recovery for each analyte, corrected for
background concentrations measured in the unfortified sample,
and compare these values to the designated LFM recovery range
of 70-130%. Recovery calculations are not required if the
concentration of the analyte added is less than 30% of the
sample background concentration. Percent recovery may be
calculated in units appropriate to the matrix, using the
following equation:
cs - c
R o x 100
s
where: R = percent recovery.
Cs = fortified sample concentration.
C = sample background concentration.
s = concentration equivalent of analyte
added to fortify the sample.
9.4.4 If recovery of any analyte falls outside the designated range
and laboratory performance for that analyte is shown to be in
control (Sect. 9.3), the recovery problem encountered with the
fortified sample is judged to be matrix related, not system re-
lated. The data user should be informed that the result for
that analyte in the unfortified sample is suspect due to either
the heterogeneous nature of the sample or an uncorrected matrix
effect.
9.4.5 Internal standards responses - The analyst is expected to
monitor the responses from the internal standards throughout
the sample set being analyzed. Ratios of the internal
standards responses against each other should also be monitored
routinely. This information may be used to detect potential
problems caused by mass dependent drift, errors incurred in
adding the internal standards or increases in the
concentrations of individual internal standards caused by
background contributions from the sample. The absolute
response of any one internal standard must not deviate more
than 60-125% of the original response in the calibration blank.
If deviations greater than these are observed, flush the
instrument with the rinse blank and monitor the responses in
the calibration blank. If the responses of the internal
standards are now within the limit, take a fresh aliquot of the
sample, dilute by a further factor of two, add the internal
standards and reanalyze. If after flushing the response of the
internal standards in the calibration blank are out of limits,
terminate the analysis and determine the cause of the drift.
Possible causes of drift may be a partially blocked sampling
cone or a change in the tuning condition of the instrument.
10.0 CALIBRATION AND STANDARDIZATION
10.1 Operating conditions - Because of the diversity of instrument
hardware, no detailed instrument operating conditions are provided.
200.8-22 Revision 5.4 May 1994
-------
The analyst is advised to follow the recommended operating conditions
provided by the manufacturer. It is the responsibility of the analyst
to verify that the instrument configuration and operating conditions
satisfy the analytical requirements and to maintain quality control
data verifying instrument performance and analytical results. Instru-
ment operating conditions which were used to generate precision and
recovery data for this method (Sect. 13) are included in Table 6.
10.2 Precalibration routine - The following precalibration routine must be
completed prior to calibrating the instrument until such time it can
be documented with periodic performance data that the instrument meets
the criteria listed below without daily tuning.
10.2.1 Initiate proper operating configuration of instrument and data
system. Allow a period of not less than 30 min for the
instrument to warm up. During this process conduct mass
calibration and resolution checks using the tuning solution.
Resolution at low mass is indicated by magnesium isotopes
24,25,26. Resolution at high mass is indicated by lead
isotopes 206,207,208. For good performance adjust spectrometer
resolution to produce a peak width of approximately 0.75 amu at
5%, peak height. Adjust mass calibration if it has shifted by
more than 0.1 amu from unit mass.
10.2.2 Instrument stability must be demonstrated by running the tuning
solution (Sect. 7.7) a minimum of five times with resulting
relative standard deviations of absolute signals for all
analytes of less than 5%.
10.3 Internal Standardization - Internal standardization must be used in
all analyses to correct for instrument drift and physical
interferences. A list of acceptable internal standards is provided in
Table 3. For full mass range scans, a minimum of three internal
standards must be used. Procedures described in this method for
general application, detail the use of five internal standards;
scandium, yttrium, indium, terbium and bismuth. These were used to
generate the precision and recovery data attached to this method.
Internal standards must be present in all samples, standards and
blanks at identical levels. This may be achieved by directly adding
an aliquot of the internal standards to the CAL standard, blank or
sample solution (Method A, Sect. 10.3), or alternatively by mixing
with the solution prior to nebulization using a second channel of the
peristaltic pump and a mixing coil (Method B, Sect. 10.3). The
concentration of the internal standard should be sufficiently high
that good precision is obtained in the measurement of the isotope used
for data correction and to minimize the possibility of correction
errors if the internal standard is naturally present in the sample.
Depending on the sensitivity of the instrument, a concentration range
of 20 fj.g/1 to 200 M9/L of each internal standard is recommended.
200.8-23 Revision 5.4 May 1994
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Internal standards should'be added to blanks, samples and standards in
a like manner, so that dilution effects resulting from the addition
may be disregarded.
10.4 Calibration - Prior to initial calibration, set up proper instrument
software routines for quantitative analysis. The instrument must be
calibrated using one of the internal standard routines (Method A or B)
described in Section 10.3. The instrument must be calibrated for the
analytes to be determined using the calibration blank (Sect. 7.6.1)
and calibration standards A and B (Sect. 7.4.1) prepared at one or
more concentration levels. A minimum of three replicate integrations
are required for data acquisition. Use the average of the
integrations for instrument calibration and data reporting.
10.5 The rinse blank should be used to flush the system between solution
changes for blanks, standards and samples. Allow sufficient rinse
time to remove traces of the previous sample (Sect. 4.1.5). Solutions
should be aspirated for 30 sec prior to the acquisition of data to
allow equilibrium to be established.
11.0 PROCEDURE
11.1 Aqueous Sample Preparation - Dissolved Analytes
11.1.1 For the determination of dissolved analytes in ground and
surface waters, pipet an aliquot (> 20 ml) of the filtered,
acid preserved sample into a 50-mL polypropylene centrifuge
tube. Add an appropriate volume of (1+1) nitric acid to adjust
the acid concentration of the aliquot to approximate a 1% (v/v)
nitric acid solution (e.g., add 0.4 ml (1+1) HN03 to a 20 ml
aliquot of sample). If the direct addition procedure (Method A,
Sect. 10.3) is being used, add internal standards, cap the tube
and mix. The sample is now ready for analysis (Sect. 1.2).
Allowance for sample dilution should be made in the
calculations.
NOTE: If a precipitate is formed during acidification,
transport, or storage, the sample aliquot must be
treated using the procedure in Section 11.2 prior to
analysis.
11.2 Aqueous Sample Preparation - Total Recoverable Analytes
11.2.1 For the "direct analysis" of total recoverable analytes in
drinking water samples containing turbidity < 1 NTU, treat an
unfiltered acid preserved sample aliquot using the sample
preparation procedure described in Section 11.1.1 while making
allowance for sample dilution in the data calculation. For the
determination of total recoverable analytes in all other
aqueous samples or for preconcentrating drinking water samples
prior to analysis follow the procedure given in Sections 11.2.2
through 11.2.8.
200.8-24 Revision 5.4 May 1994
-------
11.2.2 For the determination of total recoverable analytes in aqueous
samples (other than drinking water with < 1 NTU turbidity),
transfer a 100-mL (± 1 ml) aliquot from a well mixed, acid
preserved sample to a 250-mL Griffin beaker (Sects. 1.2, 1.3,
1.7, & 1.8). (When necessary, smaller sample aliquot volumes
may be used.)
NOTE: If the sample contains undissolved solids > 1%, a well
.mixed, acid preserved aliquot containing no more than
1 g particulate material should be cautiously
evaporated to near 10 ml and extracted using the acid-
mixture procedure described in Sections 11.3.3 thru
11.3.7.
11.2.3 Add 2 ml (1+1) nitric acid and 1.0 ml of (1+1) hydrochloric
acid to the beaker containing the measured volume of sample.
Place the beaker on the hot plate for solution evaporation.
The hot plate should be located in a fume hood and previously
adjusted to provide evaporation at a temperature of
approximately but no higher than 85°C. (See the following
note.) The beaker should be covered with an elevated watch
glass or other necessary steps should be taken to prevent
sample contamination from the fume hood environment.
NOTE: For proper heating adjust the temperature control of
the hot plate such that an uncovered Griffin beaker
containing 50 ml of water placed in the center of the
hot plate can be maintained at a temperature
approximately but no higher than 85°C. (Once the beaker
is covered with a watch glass the temperature of the
water will rise to approximately 95°C.)
11.2.4 Reduce the volume of the sample aliquot to about 20 ml by
gentle heating at 85°C. DO NOT BOIL. This step takes about 2
h for a 100 ml aliquot with the rate of evaporation rapidly
increasing as the sample volume approaches 20 ml. (A spare
beaker containing 20 ml of water can be used as a gauge.)
11.2.5 Cover the lip of the beaker with a watch glass to reduce
additional evaporation and gently reflux the sample for 30
minutes. (Slight boiling may occur, but vigorous boiling must
be avoided to prevent loss of the HC1-H20 azeotrope.)
11.2.6 Allow the beaker to cool. Quantitatively transfer the sample
solution to a 50-mL volumetric flask or 50-mL class A stoppered
graduated cylinder, make to volume with reagent water, stopper
and mix.
11.2.7 Allow any undissolved material to settle overnight, or
centrifuge a portion of the prepared sample until clear. (If
after centrifuging or standing overnight the sample contains
suspended solids that would clog the nebulizer, a portion of
200.8-25 Revision 5.4 May 1994
-------
the sample may be filtered for their removal prior to analysis.
However, care should be exercised to avoid potential
contamination from filtration.)
11.2.8 Prior to analysis, adjust the chloride concentration by
pipetting 20 ml of the prepared solution into a 50-mL
volumetric flask, dilute to volume with reagent water and mix.
(If the dissolved solids in this solution are > 0.2%,
additional dilution may be required to prevent clogging of the
extraction and/or skimmer cones. If the direct addition
procedure (Method A, Sect. 10.3) is being used, add internal
standards and mix. The sample is now ready for analysis.
Because the effects of various matrices on the stability of
diluted samples cannot be characterized, all analyses should be
performed as soon as possible after the completed preparation.
11.3 Solid Sample Preparation - Total Recoverable Analytes
11.3.1 For the determination of total recoverable analytes in solid
samples, mix the sample thoroughly and transfer a portion
(> 20 g) to tared weighing dish, weigh the sample and record
the wet weight (WW). (For samples with < 35% moisture a 20 g
portion is sufficient. For samples with moisture > 35% a
larger aliquot 50-100 g is required.) Dry the sample to a
constant weight at 60°C and record the dry weight (DW) for
calculation of percent solids (Sect. 12.6). (The sample is
dried at 60°C to prevent the loss of mercury and other possible
volatile metallic compounds, to facilitate sieving, and to
ready the sample for grinding.)
11.3.2 To achieve homogeneity, sieve the dried sample using a 5-mesh
polypropylene sieve and grind in a mortar and pestle. (The
sieve, mortar and pestle should be cleaned between samples.)
From the dried, ground material weigh accurately a
representative 1.0 ± 0.01 g aliquot (W) of the sample and
transfer to a 250-mL Phillips beaker for acid extraction.
11.3.3 To the beaker add 4 ml of (1+1) HN03 and 10 ml of (1+4) HC1.
Cover the lip of the beaker with a watch glass. Place the
beaker on a hot plate for reflux extraction of the analytes.
The hot plate should be located in a furne hood and previously
adjusted to provide a reflux temperature of approximately
95°C. (See the following note.)
NOTE: For proper heating adjust the temperature control of
the hot plate such that an uncovered Griffin beaker
containing 50 ml of water placed in the center of the
hot plate can be maintained at a temperature
approximately but no higher than 85°C. (Once the beaker
is covered with a watch glass the temperature of the
water will rise to approximately 95°C.) Also, a block
digester capable of maintaining a temperature of 95°C
200.8-26 Revision 5.4 May 1994
-------
and equipped with 250-mL constricted volumetric
digestion tubes may be substituted for the hot plate
and conical beakers in the extraction step.
11.3.4 Heat the sample and gently reflux for 30 min. Very slight
boiling may occur, however vigorous boiling must be avoided to
prevent loss of the HC1-H?0 azeotrope. Some solution
evaporation will occur (3 to 4 ml).
11.3.5 Allow the sample to cool and quantitatively transfer the
extract to a 100-mL volumetric flask. Dilute to volume with
reagent water, stopper and mix.
11.3.6 Allow the sample extract solution to stand overnight to
separate insoluble material or centrifuge a portion of the
sample solution until clear. (If after centrifuging or
standing overnight the extract solution contains suspended
solids that would clog the nebulizer, a portion of the extract
solution may be filtered for their removal prior to analysis.
However, care should be exercised to avoid potential
contamination from filtration.)
11.3.7 Prior to analysis, adjust the chloride concentration by
pipetting 20 ml of the prepared solution into a 100-mL
volumetric flask, dilute to volume with reagent water and mix.
(If the dissolved solids in this solution are > 0.2%,
additional dilution may be required to prevent clogging of the
extraction and/or skimmer cones. If the direct addition
procedure (Method A, Sect. 10.3) is being used, add internal
standards and mix. The sample extract is now ready for
analysis. Because the effects of various matrices on the
stability of diluted samples cannot be characterized, all
analyses should be performed as soon as possible after the
completed preparation.
NOTE: Determine the percent solids in the sample for use in
calculations and for reporting data on a dry weight
basis.
11.4 Sample Analysis
11.4.1 For every new or unusual matrix, it is highly recommended that
a semi-quantitative analysis be carried out to screen the
sample for elements at high concentration. Information gained
from this may be used to prevent potential damage to the
detector during sample analysis and to identify elements which
may be higher than the linear range. Matrix screening may be
carried out by using intelligent software, if available, or by
diluting the sample by a factor of 500 and analyzing in a semi-
quantitative mode. The sample should also be screened for
background levels of all elements chosen for use as internal
standards in order to prevent bias in the calculation of the
analytical data.
200.8-27 Revision 5.4 May 1994
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11.4.2 Initiate instrument operating configuration. Tune and
calibrate the instrument for the analytes of interest (Sect.
10.0).
11.4.3 Establish instrument software run procedures for quantitative
analysis. For all sample analyses, a minimum of three
replicate integrations are required for data acquisition. Use
the average of the integrations for data reporting.
11.4.4 All masses which might affect data quality must be monitored
during the analytical run. As a minimum, those masses
prescribed in Table 4 must be monitored in the same scan as is
used for the collection of the data. This information should
be used to correct the data for identified interferences.
11.4.5 During the analysis of samples, the laboratory must comply with
the required quality control described in Sections 9.3 and 9.4.
Only for the determination of dissolved analytes or the "direct
analysis" of drinking water with turbidity of < 1 NTU is the
sample digestion step of the LRB, LFB, and LFM not required.
11.4.6 The rinse blank should be used to flush the system between
samples. Allow sufficient time to remove traces of the previous
sample or a minimum of one minute (Sect. 4.1.5). Samples
should be aspirated for 30 sec prior to the collection of data.
11.4.7 Samples having concentrations higher than the established
linear dynamic range should be diluted into range and
reanalyzed. The sample should first be analyzed for the trace
elements in the sample, protecting the detector from the high
concentration elements, if necessary, by the selection of
appropriate scanning windows. The sample should then be
diluted for the determination of the remaining elements.
Alternatively, the dynamic range may be adjusted by selecting
an alternative isotope of lower natural abundance, provided
quality control data for that isotope have been established.
The dynamic range must not be adjusted by altering instrument
conditions to an uncharacterized state.
12.0 DATA ANALYSIS AND CALCULATIONS
12.1 Elemental equations recommended for sample data calculations are
listed in Table 5. Sample data should be reported in units of jug/L
for aqueous samples or mg/kg dry weight for solid samples. Do not
report element concentrations below the determined MDL.
12.2 For data values less than ten, two significant figures should be used
for reporting element concentrations. For data values greater than or
equal to ten, three significant figures should be used.
12.3 For aqueous samples prepared by total recoverable procedure (Sect.
11.2), multiply solution concentrations by the dilution factor 1.25.
If additional dilutions were made to any samples or an aqueous sample
200.8-28 Revision 5.4 May 1994
-------
was prepared using the acid-mixture procedure described in Section
11.3, the appropriate factor should be applied to the calculated
sample concentrations.
12.4 For total recoverable analytes in solid samples (Sect. 11.3), round
the solution analyte concentrations (ng/l in the analysis solution)
as instructed in Section 12.2. Multiply the #/L concentrations in the
analysis solution by the factor 0.005 to calculate the mg/L analyte
concentration in the 100-mL extract solution. (If additional dilutions
were made to any samples, the appropriate factor should be applied to
calculate analyte concentrations in the extract solution.) Report
the data up to three significant figures as mg/kg dry-weight basis
unless specified otherwise by the program or data user. Calculate the
concentration using the equation below:
C x V
Sample Cone, ^mg/kg) =
dry-weight basis W
where: C = Concentration in the extract (mg/L)
V = Volume of extract (L, 100 ml = 0.1L)
W = Weight of sample aliquot extracted (g x 0.001 = kg)
Do not report analyte data below the estimated solids MDL or an
adjusted MDL because of additional dilutions required to complete the
analysis.
12.5 To report^percent solids in solid samples (Sect. 11.3) calculate as
follows:
DW
% solids (S) = x 100
WW
where: DW = Sample weight (g) dried at 60°C
WW = Sample weight (g) before drying
NOTE: If the data user, program or laboratory requires that the
reported percent solids be determined by drying at 105°C,
repeat the procedure given in Section 11.3 using a separate
portion (> 20 g) of the sample and dry to constant weight at
103-105°C.
12.6 Data values should be corrected for instrument drift or sample matrix
induced interferences by the application of internal standardization.
Corrections for characterized spectral interferences should be applied
to the data. Chloride interference corrections should be made on all
samples, regardless of the addition of hydrochloric acid, as the
chloride ion is a common constituent of environmental samples.
12.7Jf an element has more than one monitored isotope, examination of the
concentration calculated for each isotope, or the isotope ratios, will
provide useful information for the analyst in detecting a possible
spectral interference. Consideration should therefore be given to
200.8-29 Revision 5.4 May 1994
-------
both primary and secondary isotopes in the evaluation of the element
concentration. In some cases, secondary isotopes may be less
sensitive or more prone to interferences than the primary recommended
isotopes, therefore differences between the results do not necessarily
indicate a problem with data calculated for the primary isotopes.
12.8 The QC data obtained during the analyses provide an indication of the
quality of the sample data and should be provided with the sample
results.
13.0 METHOD PERFORMANCE
13.1 Instrument operating conditions used for single laboratory testing of
the method are summarized in Table 6. Total recoverable digestion and
"direct analysis" MDLs determined using the procedure described in
Sect. 9.2.4, are listed in Table 7.
13.2 Data obtained from single laboratory testing of the method are
summarized in Table 9 for five water samples representing drinking
water, surface water, ground water and waste effluent. Samples were
prepared using the procedure described in Sect. 11.2. For each
matrix, five replicates were analyzed and the average of the
replicates used for determining the sample background concentration
for each element. Two further pairs of duplicates were fortified at
different concentration levels. For each method element, the sample
background concentration, mean percent recovery, the standard
deviation of the percent recovery and the relative percent difference
between the duplicate fortified samples are listed in Table 8.
13.3 Data obtained from single laboratory testing of the method are
summarized in Table 10 for three solid samples consisting of SRM 1645
River Sediment, EPA Hazardous Soil and EPA Electroplating Sludge.
Samples were prepared using the procedure described in Sect. 11.3.
For each method element, the sample background concentration, mean
percent recovery, the standard deviation of the percent recovery and
the relative percent difference between the duplicate fortified
samples were determined as for Sect. 13.2.
13.4 Data obtained from single laboratory testing of the method for
drinking water analysis using the "direct analysis" procedure (Sect.
11.2.1) are given in Table 11. Three drinking water samples of
varying hardness collected from Regions 4, 6, and 10 were fortified to
contain 1 ng/L of all metal primary contaminants, except selenium,
which was added to a concentration of 20 /jg/L. For each matrix, four
replicate aliquots were analyzed to determine the sample background
concentration of each analyte and four fortified aliquots were
analyzed to determine mean percent recovery in each matrix. Listed
in the Table 11 are the average mean percent recovery of each analyte
in the three matrices and the standard deviation of the mean percent
recoveries.
13.5 Listed in Table 12 are the regression equations for precision and bias
developed from the joint USEPA/Association of Official Analytical
Chemists (AOAC) multilaboratory validation study conducted on this
200.8-30 Revision 5.4 May 1994
-------
method. These equations were developed from data received from 13
laboratories on reagent water, drinking water and ground water.
Listed in Tables 13 and 14, respectively, are the precision and
recovery data from a wastewater digestate supplied to all laboratories
and from a wastewater of the participant's choice. For a complete
review of the study see reference 11. Section 16.0 of this method.
14.0 POLLUTION PREVENTION
14.1 Pollution prevention encompasses any technique that reduces or
eliminates the quantity or toxicity of waste at the point of
generation. Numerous opportunities for pollution prevention exist in
laboratory operation. The EPA has established a preferred hierarchy
of environmental management techniques that places pollution
prevention as the management option of first choice. Whenever
feasible, laboratory personnel should use pollution prevention
techniques to address their waste generation. When wastes cannot be
feasibly reduced at the source, the Agency recommends recycling as the
next best option.
14.2 For information about pollution prevention that may be applicable to
laboratories and research institutions, consult Less is Better:
Laboratory Chemical Management for Waste Reduction, available from the
American Chemical Society's Department of Government Relations and
Science Policy, 1155 16th Street N.W., Washington D.C. 20036,
(202)872-4477.
15.0 WASTE MANAGEMENT
15.1 The Environmental Protection Agency requires that laboratory waste
management practices be conducted consistent with all applicable rules
and regulations. The Agency urges laboratories to protect the air,
water, and land by minimizing and controlling all releases from hoods
and bench operations, complying with the letter and spirit of any
sewer discharge permits and regulations, and by complying with all
solid and hazardous waste regulations, particularly the hazardous
waste identification rules and land disposal restrictions. For
further information on waste management consult The Haste Management
Manual for Laboratory Personnel, available from the American Chemical
Society at the address listed in the Section 14.2.
16.0 REFERENCES
1. Gray, A.L. and A. R. Date. Inductively Coupled Plasma Source Mass
Spectrometry Using Continuum Flow Ion Extraction. Analyst 108 1033-
1050, 1983.
2. Houk, R.S. et al. Inductively Coupled Argon Plasma as an Ion Source
for Mass Spectrometric Determination of Trace Elements. Anal Chem. 52
2283-2289, 1980. ~~
200.8-31 Revision 5.4 May 1994
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3. Houk, R.S., Mass Spectrometry of Inductively Coupled Plasmas. Anal,
Chem. 58 97A-105A, 1986.
4. Thompson, J.J. and R. S. Houk. A Study of Internal Standardization in
Inductively Coupled Plasma-Mass Spectrometry. Appl. Spec. 41 801-806.
1987.
5. Carcinogens - Working With Carcinogens, Department of Health,
Education, and Welfare, Public Health Service, Center for Disease
Control, National Institute for Occupational Safety and Health,
Publication No. 77-206, Aug. 1977. Available from the National
Technical Information Service (NTIS) as PB-277256.
6. OSHA Safety and Health Standards, General Industry, (29 CFR
1910), Occupational Safety and Health Administration, OSHA 2206,
(Revised, January 1976).
7. Safety in Academic Chemistry Laboratories, American Chemical
Society Publication, Committee on Chemical Safety, 3rd Edition,
1979.
8. Proposed OSHA Safety and Health Standards, Laboratories, Occupational
Safety and Health Administration, Federal Register, July 24, 1986.
9. American Society for Testing and Materials. Standard Specification
for Reagent Water, D1193-77. Annual Book of ASTM Standards, Vol.
11.01. Philadelphia, PA, 1991.
10. Code of Federal Regulations 40, Ch. 1, Pt. 136 Appendix B.
11. Longbottom, J.E. et. al. Determination of Trace Elements in Water by
Inductively Coupled Plasma-Mass Spectrometry: Collaborative Study,
Journal of AOAC International 77 1004-1023, 1994.
12. Hinners, T.A., Interferences in ICP-MS by Bromine Species. Winter
Conference on Plasma Spectrochemistry, San Diego, CA, January, 10-15,
1994.
200.8-32 Revision 5.4 May 1994
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17.0 TABLES. DIAGRAMS. FLOWCHARTS. AND VALIDATION DATA
TABLE 1: ESTIMATED INSTRUMENT DETECTION LIMITS
ELEMENT
RECOMMENDED
ANALYTICAL MASS
ESTIMATED IDLs (0g/L)
SCANNING
MODE1
SELECTIVE ION
MONITORING MODE2'3
Aluminum
Antimony
Arsenic*3'
Barium
Beryl 1i urn
Cadmium
Chromium
Cobalt
Copper
Lead
Manganese
Mercury
Molybdenum
Nickel
Selenium<3>
Silver
Thallium
Thorium
Uranium
Vanadium
Zinc
27
123
75
137
9
111
52
59
63
206.207,208
55
202
98
60
82
107
205
232
238
51
66
0.05
0.08
0.9
0.5
0.1
0.1
0.07
0.03
0.03
0.08
0.1
n.a.
0.
0.
5
0.05
0.09
0.03
0.02
0.02
0.2
0.02
0.008
0.02
0.03
0.02
0.02
0.04
0.002
0.004
0.015
0.007
0.2
0.005
0.07
1.3
0.004
0.014
0.005
0.005
0.006
0.07
Instrument detection limits (3cr) estimated from seven replicate
integrations of the blank (1% v/v nitric acid) following calibration of the
instrument with three replicate integrations of a multi-element standard.
1 Instrument operating conditions and data acquisition mode are given in
Table 6.
2 IDLs7determined using state-of-the-art instrumentation (1994). D;
for As, Se, and Se were acquired using a dwell time of 4.096
with 1500 area count per sec B3Kr present in argon supply. All <
Data
sec
. . Per sec Kr present in argon supply. All other
data were acquired using a dwell time of 1.024 sec per AMU monitored.
200.8-33
Revision 5.4 May 1994
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TABLE 2: COMMON MOLECULAR ION INTERFERENCES IN ICP-MS
BACKGROUND MOLECULAR IONS
Molecular Ion
NH*
OH*
OH2+
C2+
CM*
C0+
N2*
N2H*
N0+
NOH*
°2+
02H*
36ArH+
38ArH+
40ArH+
C02+
C02H+
ArC+,ArO+
ArN+
ArNH*
ArO*
ArOH*
AOAr36Ar+
40Ar38Ar+
«Ar2*
Mass Element Interference3
15
17
18
24
26
28
28
29
30
31
32
33
37
39
41
44
45 Sc
52 Cr
54 Cr
55 Mn
56
57
76 Se
78 Se
80 Se
method elements or internal standards affected by the molecular ions.
200.8-34 Revision 5.4 May 1994
-------
TABLE 2 (Continued),
MATRIX MOLECULAR IONS
BROMIDE12
Molecular Ion
81BrH+
8iBr°I
81BrOH*
Ar81Br+
CHLORIDE
Molecular Ion
L 1 0
3*C10H+
37C10*
37C10H+
Ar35Cl +
Ar37Cl+
SULPHATE
Molecular Ion
so*
32SOH+
34SOH+
S02+, S2+
Ar32S+
Ar34S+
PHOSPHATE
Molecular Ion
P0+
POHj
P02+
ArP+
GROUP I, II METALS
Molecular Ion
ArNa*
ArK+
ArCa*
Mass
82
95
97
98
121
Mass
51
52
53
54
75
77
Mass
48
49
50
51
64
72
74
Mass
47
48
63
71
Mass
63
79
80
Element Interference
Se
Mo
Mo
Mo
Sb
Element Interference
v
V
Cr
Cr
Cr
As
Se
Element Interference
V,Cr
v
Zn
Element Interference
Cu
Element Interference
Cu
200.8-35
Revision 5.4 May 1994
-------
TABLE 2 (Continued).
MATRIX MOLECULAR IONS
MATRIX OXIDES
Molecular Ion Masses Element Interference
TiO 62-66 Ni.Cu.Zn
ZrO 106-112 Ag,Cd
MoO 108-116 Cd
Oxide interferences will normally be very small and will only impact the
method elements when present at relatively high concentrations. Some examples
of matrix oxides are listed of which the analyst should be aware. It is
recommended that Ti and Zr isotopes are monitored in solid waste samples,
which are likely to contain high levels of these elements. Mo is monitored as
a method analyte.
200.8-36 Revision 5.4 May 1994
-------
TABLE 3: INTERNAL STANDARDS AND LIMITATIONS OF USE
Internal Standard Mass Possible Limitation
6Lithium 6 a
Scandium 45 polyatomic ion interference
Yttrium 89 a b
Rhodium 103
indjum 115 isobaric interference by Sn
Terbium 159
Holmium 155
Lutetium 175
Bismuth 209 a
a May be present in environmental samples.
b Jnu+°me instruments Yttrium may form measurable amounts of Y0+ (105 amu)and
YOH (106 amu). If this is the case, care should be taken in the use of the
cadmium elemental correction equation.
Internal standards recommended for use with this method are shown in bold
face. Preparation procedures for these are included in Section 7.3.
200.8-37 Revision 5.4 May 1994
-------
TABLE 4: RECOMMENDED ANALYTICAL ISOTOPES AND ADDITIONAL
MASSES WHICH MUST BE MONITORED
Isotope
27
121.123
75
135.137
9
106,108,111,114
52,53
59
63,65
206.207.208
55
95,97,98
60,62
77,82
107.109
203.205
232
238
51
66,67,68
83
99
105
118
Element of Interest
Aluminum
Antimony
Arsenic
Barium
Beryl 1i urn
Cadmium
Chromium
Cobalt
Copper
Lead
Manganese
Molybdenum
Nickel
Selenium
Silver
Thai 1i urn
Thorium
Uranium
Vanadium
Zinc
Krypton
Ruthenium
Palladium
Tin
NOTE: Isotopes recommended for analytical determination are underlined.
200.8-38
Revision 5.4 May 1994
-------
TABLE 5: RECOMMENDED ELEMENTAL EQUATIONS FOR DATA CALCULATIONS
El ement
Al
Sb
As
Ba
Be
Cd
Cr
Co
Cu
Pb
Mn
Mo
Ni
Se
Ag
Tl
Th
U
V
Zn
Elemental Equation
(1.000)(27C)
(1.000)(123C)
(1.000)(75C)-(3.127)[(77C)-(0.815)(82C)]
(1.000)(137C)
(1.000)(9C)
(1.000)(111C)-(1.073)[(108C)-(0.712)(106C)]
(1.000)(52C)
(1.000)(59C)
(1.000)(63C)
(1.000)(206C)+(1.000)(207C)+{1.000)(208C)
(1.000)(55C)
(1.000)(98C)-(0.146)(99C)
(1.000)(60C)
(1.000)(82C)
(1.000)(107C)
(1.000)(205C)
(1.000)(232C)
(1.000)(238C)
(1.000)(51C)-(3.127)[(53C)-(0.113)(52C)]
(1.000)(66C)
Note
(1)
(2)
(3)
(4)
(5)
(6)
(7)
200.8-39 Revision 5.4 May 1994
-------
TABLE 5 (Continued)
INTERNAL STANDARDS
Element Elemental Equation Note
Bi (1.000)(209C)
In (1.000)(115C)-(0.016)(118C) (8)
Sc (1.000)(45C)
Tb (1.000)(159C)
Y (1.000)(89C)
C - calibration blank subtracted counts at specified mass.
(1) - correction for chloride interference with adjustment for
^Se. ArCl 75/77 ratio may be determined from the reagent+
blank. Isobaric mass 82 must be from Se only and not BrH .
(2) - correction for MoO interference. Isobaric mass 106 must be from Cd
only not ZrO+. An additional isobaric elemental correction should
be made if palladium is present.
(3) - in 0.4% v/v HC1, the background from C10H will normally be
small. However the contribution may be estimated from the+
reagent blank. Isobaric mass must be from Cr only not ArC .
(4) - allowance for isotopic variability of lead isotopes.
(5) - isobaric elemental correction for ruthenium.
(6) - some argon supplies contain krypton as an impurity. Selenium
is corrected for 82Kr by background subtraction.
(7) - correction for chloride interference with adjustment for
53Cr. CIO 51/53 ratio may be determined from the reagent
blank. Isobaric mass 52 must be from Cr only not ArC*.
(8) - isobaric elemental correction for tin.
200.8-40 Revision 5.4 May 1994
-------
TABLE 6: INSTRUMENT OPERATING CONDITIONS
FOR PRECISION AND RECOVERY DATA1
Instrument VG PlasmaQuad Type I
Plasma forward power 1.35 kW
Coolant flow rate 13.5 L/min
Auxiliary flow rate 0.6 L/min
Nebulizer flow rate 0.78 L/min
Solution uptake rate 0.6 mL/min
Spray chamber temperature 15°C
Data Acquisition
Detector mode Pulse counting
Replicate integrations 3
Mass range 8 - 240 amu
Dwell time 320 ^s
Number of MCA channels 2048
Number of scan sweeps 85
Total acquisition time 3 minutes per sample
The described instrument and operating conditions were used to
determine the scanning mode MDL data listed in Table 7 and the
precision and recovery data given in Tables 9 and 10.
200.8-41 Revision 5.4 May 1994
-------
TABLE 7: METHOD DETECTION LIMITS
""ELEMENT
SCANNING MODE1
TOTAL RECOVERABLE
AQUEOUS SOLIDS
SELECTIVE ION MONITORING MODE2
TOTAL RECOVERABLE DIRECT ANALYSIS3
AQUEOUS AQUEOUS
27 AT
123 Sb
75 As
137 Ba
9 Be
111 Cd
52 Cr
59 Co
63 Cu
206,207,208 pL
55 Mn
202 Hg
98 Mo
60 Ni
82 Se
107 Ag
205 Tl
232 Th
238 ,j
51 V
66 In
1.0
0.4
1.4
0.8
0.3
0.5
0.9
0.09
0.5
0.6
0.1
n.a.
0.3
0.5
7.9
0.1
0.3
0.1
0.1
2.5
1.8
0.4
0.2
0.6
0.4
0.1
0.2
0.4
0.04
0.2
0.3
0.05
n.a.
0.1
0.2
3.2
0.05
0.1
0.05
0.05
1.0
0.7
1.7
0.04
0.4
0.04
0.02
0.03
0.08
0.004
0.02
0.05
0.02
n.a.
0.01
0.06
2.1 '
0.005
0.02
0.02
0.01
0.9
0.1
0.04
0.02
0.1
0.04
0.03
0.03
0.08
0.003
0.01
0.02
0.04
0.2
0.01
0.03
0.5
0.005
0.01
0.01
0.01
0.05
0.2
1 Data acquisition mode given in Table 6. Total recoverable MDL concentrations
are computed for original matrix with allowance for sample dilution during
preparation. Listed MDLs for solids calculated from determined aqueous MDLs.
2 MDLs determined using state-of-the-art instrumentation (1994). Data for
82Se were acquired using a dwell time of 4.096 sec with 1500
^
, Se, and
area count per sec 83Kr present in argon supply. All other data were
acquired using a dwell time of 1.024 sec per AMU monitored.
3 MDLs were determined from analysis of 7 undigested aqueous sample aliquots
n.a.- not applicable. Total recoverable digestion not suitable for organo-
mercury compounds.
200.8-42
Revision 5.4 May 1994
-------
TABLE 8: ACCEPTANCE LIMITS FOR QC CHECK SAMPLE
METHOD PERFORMANCE (/tg/L)1
QC Check
Sample Average
ELEMENT Cone. Recovery
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium
Cobalt
Copper
Lead
Manganese
Molybdenum
Nickel
Selenium
Silver
Thallium
Thorium
Uranium
Vanadium
Zinc
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100.4
99.9
101.6
99.7
105.9
100.8
102.3
97.7
100.3
104.0
98.3
101.0
100.1
103.5
101.1
98.5
101.4
102.6
100.3
105.1
Standard
Deviation2
(Sr)
5.49
2.40
3.66
2.64
4.13
2.32
3.91
2.66
2.11
3.42
2.71
2.21
2.10
5.67
3.29
2.79
2.60
2.82
3.26
4.57
Acceptance
Limits3
Jt/O/L
84-117
93-107
91-113
92-108
88-1124
94-108
91-114
90-106
94-107
94-114
90-106
94-108
94-106
86-121
91-1115
90-107
94-109
94-111
90-110
91-119
1 Method performance characteristics calculated using regression
equations from collaborative study, reference 11.
Single-analyst standard deviation, Sr.
Acceptance limits calculated as average recovery _+3 standard deviations.
Acceptance limits centered at 100% recovery.
Statistics estimated from summary statistics at 48 and 64 //g/L.
200.8-43
Revision 5.4 May 1994
-------
TABLE 9 : PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES
DRINKING WATER
El ement
Al
Sb
As
Ba
Be
Cd
Cr
Co
Cu
Pb
Mn
Mo
Ni
Se
Ag
Tl
Th
U
V
Zn
Samp! e Low
Concn. Spike
(fld/U (fld/U
175
<0.4
<1.4
43.8
<0.3
<0.5
<0.9
0.11
3.6
0.87
0.96
1.9
1.9
<7.9
<0.1
<0.3
<0.1
0.23
<2.5
5.2
50
10
50
50
10
10
10
10
10
10
10
10
10
50
50
10
10
10
50
50
Average
Recovery
R (%)
115.8
99.1
99.7
94.8
113.5
97.0
111.0
94.4
101.8
97.8
96.9
99.4
100.2
99.0
100.7
97.5
109.0
110.7
101.4
103.4
S(R)
5.9
0.7
0.8
3.9
0.4
2.8
3.5
0.4
8.8
2.0
1.8
1.6
5.7
1.8
1.5
0.4
0.7
1.4
0.1
3.3
High
RPD Spike
(ua/l)
0.4
2.0
2.2
5.8
0.9
8.3
9.0
1.1
17.4
2.8
4.7
3.4
13.5
5.3
4.2
1.0
1.8
3.5
0.4
7.7
200
100
200
200
100
100
100
100
100
100
100
100
100
200
200
100
100
100
200
200
Average
Recovery
R m
102.7
100.8
102.5
95.6
111.0
101.5
99.5
93.6
91.6
99.0
95.8
98.6
95.2
93.5
99.0
98.5
106.0
107.8
97.5
96.4
S(R)
1.6
0.7
1.1
0.8
0.7
0.4
0.1
0.5
0.3
0.8
0.6
0.4
0.5
3.5
0.4
1.7
1.4
0.7
0.7
0.5
RPD
1.1
2.0
2.9
1.7
1.8
1.0
0.2
1.4
0.3
2.2
1.8
1.0
1.3
10.7
1.0
4.9
3.8
1.9
2.1
1.0
S(R) Standard deviation of percent recovery.
RPD Relative percent difference between duplicate spike determinations.
< Sample concentration below established method detection limit.
200.8-44
Revision 5.4 May 1994
-------
TABLE 9 : PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont).
WELL HATER
Element
Al
Sb
As
Ba
Be
Cd
Cr
Co
Cu
Pb
Mn
Mo
Ni
Se
Ag
Tl
Th
U
V
Zn
Sample Low
Concn. Spike
(UQ/l) (UQ/U
34.3
0.46
<1.4
106
<0.3
1.6
<0.9
2.4
37.4
3.5
2770
2.1
11.4
<7.9
<0.1
<0.3
<0.1
1.8
<2.5
554
50
10
50
50
10
10
10
10
10
10
10
10
10
50
50
10
10
10
50
50
Average
Recovery
R m
100.1
98.4
110.0
95.4
104.5
88.6
111.0
100.6
104.3
95.2
*
103.8
116.5
127.3
99.2
93.9
103.0
106.0
105.3
*
S(R)
3.9
0.9
6.4
3.9
0.4
1.7
0.0
1.0
5.1
2.5
*
1.1
6.3
8.4
0.4
0.1
0.7
1.1
0.8
*
High
RPD Spike
(ua/l)
0.8
1.9
16.4
3.3
1.0
3.8
0.0
1.6
1.5
1.5
1.8
1.6
6.5
18.7
1.0
0.0
1.9
1.6
2.1
1.2
200
100
200
200
100
100
100
100
100
100
100
100
100
200
200
100
100
100
200
200
Average
Recovery
R m
102.6
102.5
101.3
104.9
101.4
98.6
103.5
104.1
100.6
99.5
*
102.9
99.6
101.3
101.5
100.4
104.5
109.7
105.8
102.1
S(R)
1.1
0.7
0.2
1.0
1.2
0.6
0.4
0.4
0.8
1.4
*
0.7
0.3
0.2
1.4
1.8
1.8
2.5
0.2
5.5
RPD
1.3
1.9
0.5
1.6
3.3
1.6
1.0
0.9
1.5
3.9
0.7
1.9
0.0
0.5
3.9
5.0
4.8
6.3
0.5
3.2
S(R) Standard deviation of percent recovery.
RPD Relative percent difference between duplicate spike determinations.
< Sample concentration below established method detection limit.
* Spike concentration <10% of sample background concentration.
200.8-45
Revision 5.4 May 1994
-------
TABLE 9 : PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont).
POND WATER
Element
Al
Sb
As
Ba
Be
Cd
Cr
Co
Cu
Pb
Mn
Mo
Ni
Se
Ag
Tl
Th
U
V
Zn
Sampl e Low
Concn. Spike
(ua/L) fuq/L)
610
<0.4
<1.4
28.7
<0.3
<0.5
2.0
0.79
5.4
1.9
617
0.98
2.5
<7.9
0.12
<0.3
0.19
0.30
3.5
6.8
50
10
50
50
10
10
10
10
10
10
10
10
10
50
50
10
10
10
50
50
Average
Recovery
R m
*
101.1
100.8
102.1
109.1
106.6
107.0
101.6
107.5
108.4
*
104.2
102.0
102.7
102.5
108.5
93.1
107.0
96.1
99.8
S(R)
*
1.1
2.0
1.8
0.4
3.2
1.0
1.1
1.4
1.5
*
1.4
2.3
5.6
0.8
3.2
3.5
2.8
5.2
1.7
High
RPD Spike
llM/L)
1.7
2.9
5.6
2.4
0.9
8.3
1.6
2.7
1.9
3.2
1.1
3.5
4.7
15.4
2.1
8.3
10.5
7.3
14.2
3.7
200
100
200
200
100
100
100
100
100
100
100
100
100
200
200
100
100
100
200
200
Average
Recovery
R m
78.2
101.5
96.8
102.9
114.4
105.8
100.0
101.7
98.1
106.1
139.0
104.0
102.5
105.5
105.2
105.0
93.9
107.2
101.5
100.1
S(R)
9.2
3.0
0.9
3.7
3.9
2.8
1.4
1.8
2.5
0.0
11.1
2.1
2.1
1.4
2.7
2.8
1.6
1.8
0.2
2.8
RPD
5.5
8.4
2.6
9.0
9.6
7.6
3.9
4.9
6.8
0.0
4.0
5.7
5.7
3.8
7.1
7.6
4.8
4.7
0.5
7.7
S(R) Standard deviation of percent recovery.
RPD Relative percent difference between duplicate spike determinations.
< Sample concentration below established method detection limit.
* Spike concentration <10% of sample background concentration.
200.8-46
Revision 5.4 May 1994
-------
TABLE 9 : PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont).
SEWAGE TREATMENT PRIMARY EFFLUENT
El ement
Al
Sb
As
Ba
Be
Cd
Cr
Co
Cu
Pb
Mn
Mo
Ni
Se
Ag
Tl
Th
U
V
Zn
Sampl e Low
Concn. Spike
(UQ/L) (ua/l)
1150
1.5
<1.4
202
<0.3
9.2
128
13.4
171
17.8
199
136
84.0
<7.9
10.9
<0.3
0.11
0.71
<2.5
163
50
10
50
50
10
10
10
10
10
10
10
10
10
50
50
10
10
10
50
50
Average
Recovery
R m
*
95.7
104.2
79.2
110.5
101.2
*
95.1
*
95.7
*
*
88.4
112.0
97.1
97.5
15.4
109.4
90.9
85.8
S(R)
*
0.4
4.5
9.9
1.8
1.3
*
2.7
*
3.8
*
*
16.3
10.9
0.7
0.4
1.8
1.8
0.9
3.3
High
RPD Spike
(ULQ/l)
3.5
0.9
12.3
2.5
4.5
0.0
1.5
2.2
2.4
1.1
1.5
1.4
4.1
27.5
1.5
1.0
30.3
4.3
0.6
0.5
200
100
200
200
100
100
100
100
100
100
100
100
100
200
200
100
100
100
200
200
Average
Recovery
R m
100.0
104.5
101.5
108.6
106.4
102.3
102.1
99.1
105.2
102.7
103.4
105.7
98.0
108.8
102.6
102.0
29.3
109.3
99.4
102.0
S(R)
13.8
0.7
0.7
4.6
0.4
0.4
1.7
1.1
7.1
1.1
2.1
2.4
0.9
3.0
1.4
0.0
0.8
0.7
2.1
1.5
RPD
1.5
1.9
2.0
5.5
0.9
0.9
0.4
2.7
0.7
2.5
0.7
2.1
0.0
7.8
3.7
0.0
8.2
1.8
6.0
1.9
S(R) Standard deviation of percent recovery.
RPD Relative percent difference between duplicate spike determinations.
< Sample concentration below established method detection limit.
* Spike concentration <10% of sample background concentration.
200.8-47
Revision 5.4 May 1994
-------
TABLE 9 : PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont).
INDUSTRIAL EFFLUENT
Element
AT
Sb
As
Ba
Be
Cd
Cr
Co
Cu
Pb
Mn
Mo
Ni
Se
Ag
Tl
Th
U
V
Zn
Sampl e Low
Concn. Spike
(UQ/l) (tfq/L)
44.7
2990
<1.4
100
<0.3
10.1
171
1.3
101
294
154
1370
17.3
15.0
<0.1
<0.3
0.29
0.17
<2.5
43.4
50
10
50
50
10
10
10
10
10
10
10
10
10
50
50
10
10
10
50
50
Average
Recovery
R m
98.8
*
75.1
96.7
103.5
106.5
*
90.5
*
*
*
*
107.4
129.5
91.8
90.5
109.6
104.8
74.9
85.0
S(R)
8.7
*
1.8
5.5
1.8
4.4
*
3.2 '
*
*
*
*
7.4
9.3
0.6
1.8
1.2
2.5
0.1
4.0
High
RPD Spike
(UQ/l)
5.7
0.3
6.7
3.4
4.8
2.4
0.0
8.7
0.9
2.6
2.8
1.4
5.0
15.1
1.7
5.5
2.7
6.6
0.3
0.6
200
100
200
200
100
100
100
100
100
100
100
100
100
200
200
100
100
100
200
200
Average
Recovery
R M
90.4
*
75.0
102.9
100.0
97.4
127.7
90.5
92.5
108.4
103.6
*
88.2
118.3
87.0
98.3
108.7
109.3
72.0
97.6
S(R)
2.1
*
0.0
1.1
0.0
1.1
2.4
0.4
2.0
2.1
3.7
*
0.7
1.9
4.9
1.0
0.0
0.4
0.0
1.0
RPD
2.2
0.0
0.0
0.7
0.0
2.8
1.7
1.3
1.6
0.0
1.6
0.7
1.0
3.6
16.1
2.8
0.0
0.9
0.0
0.4
S(R) Standard deviation of percent recovery.
RPD Relative percent difference between duplicate spike determinations.
< Sample concentration below established method detection limit.
* Spike concentration <10% of sample background concentration.
200.8-48
Revision 5.4 May 1994
-------
TABLE 10 : PRECISION AND RECOVERY DATA IN SOLID MATRICES
EPA HAZARDOUS SOIL #884
Sample Low+
Element Concn. Spike
rma/kqHma/kcrt
Al
Sb
As
Ba
Be
Cd
Cr
Co
Cu
Pb
Mn
Mo
Ni
Se
Ag
Tl
Th
U
V
Zn
S(R)
RPD
5170
5.4
8.8
113
0.6
1.8
83.5
7.1
115
152
370
4.8
19.2
<3.2
1.1
0.24
1.0
1.1
17.8
128
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
Average
Recovery
R (%}
*
69.8
104.7
54.9
100.1
97.3
86.7
98.8
86.3
85.0
*
95.4
101.7
79.5
96.1
94.3
69.8
100.1
109.2
87.0
S(R)
*
2.5
5.4
63.6
0.6
1.0
16.1
1.2
13.8
45.0
*
1.5
3.8
7.4
0.6
1.1
0.6
0.2
4.2
27.7
Hi,gh+
RPD Spike
(ma/kcrt
4.7
9.1
18.6
1.5
1.4
8.3
1.9
3.4
13.9
12.7
2.9
1.0
26.4
0.5
3.1
1.3
0.0
2.3
5.5
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
Average
Recovery
R (%)
*
70.4
102.2
91.0
102.9
101.7
105.5
102.9
102.5
151.7
85.2
95.2
102.3
100.7
94.8
97.9
76.0
102.9
106.7
113.4
S(R)
*
1.8
2.2
9.8
0.4
0.4
1.3
0.7
4.2
25.7
10.4
0.7
0.8
9.4
0.8
1.0
2.2
0.0
1.3
12.9
RPD
6.5
5.4
0.5
1.0
1.0
0.0
1.8
4.6
23.7
2.2
2.0
0.8
26.5
2.3
2.9
7.9
0.0
2.4
14.1
Standard deviation of percent recovery.
Relative percent
difference betv
/een duplicate s
Dike dete
rminat
.ions.
Sample concentration below established method detection limit.
Spike concentration <10% of sample background concentration.
Not determined.
Equivalent.
200.8-49
Revision 5.4 May 1994
-------
TABLE 10 : PRECISION AND RECOVERY DATA IN SOLID MATRICES (Cont).
NBS 1645 RIVER SEDIMENT
Sampl e Low+
Element Concn. Spike
Al
Sb
As
Ba
Be
Cd
Cr
Co
Cu
Pb
Mn
Mo
Ni
Se
Ag
Tl
Th
U
V
Zn
S(R)
RPD
(mq/kqHmq/kq)
5060
21.8
67.2
54.4
0.59
8.3
29100
7.9
112
742
717
17.1
41.8
<3.2
1.8
1.2
0.90
0.79
21.8
1780
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
Average
Recovery
R m
*
73.9
104.3
105.6
88.8
92.9
*
97.6'
121.0
*
*
89.8
103.7
108.3
94.8
91.2
91.3
95.6
91.8
*
S(R)
*
6.5
13.0
4.9
0.2
0.4
*
1.3
9.1
*
*
8.1
6.5
14.3
1.6
1.3
0.9
1.8
4.6
*
High+
RPD Spike
(mq/kq)
9.3
7.6
2.8
0.5
0.0
-
2.6
1.5
-
-
12.0
4.8
37.4
4.3
3.6
2.6
5.0
5.7
—
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
Average
Recovery
R
*
81
107
98
87
95
*
103
105
-
-
98
102
93
96
94
92
98
100
*
(%)
.2
.3
.6
.9
.7
.1
.2
.4
.2
.9
.2
.4
.3
.5
.7
S(R)
*
1.5
2.1
2.2
0.1
1.4
*
0.0
2.2
_
-
0.7
0.8
5.0
0.7
0.4
0.9
1.2
0.6
*
RPD
_
3.9
2.9
3.9
0.2
3.9
-
0.0
1.8
-
-
0.9
0.0
15.1
1.9
1.3
2.8
3.5
0.8
—
Standard deviation of percent recovery.
Relative percent
difference between duplicate
spike
determinations.
Sample concentration below established method detection limit.
Spike concentration <10% of sample background concentration.
Not determined.
Equivalent.
200.8-50
Revision 5.4 May 1994
-------
TABLE 10 : PRECISION AND RECOVERY DATA IN SOLID MATRICES (Cont).
EPA ELECTROPLATING SLUDGE #286
Sampl e Low+
Element Concn. Spike
(mq/kaHma/kcn
Al
Sb
As
Ba
Be
Cd
Cr
Co
Cu
Pb
Mn
Mo
Ni
Se
Ag
Tl
Th
U
V
Zn
S(R)
RPD
5110
8.4
41.8
27.3
0.25
112
7980
4.1
740
1480
295
13.3
450
3.5
5.9
1.9
3.6
2.4
21.1
13300
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
Average
Recovery
R (%)
*
55.4
91.0
1.8
92.0
85.0
*
89.2
*
*
*
82.9
*
89.7
89.8
96.9
91.5
107.7
105.6
*
S(R)
*
1.5
2.3
7.1
0.9
5.2
*
1.8
*
*
*
1.2
*
3.7
2.1
0.9
1.3
2.0
1.8
*
High+
RPD Spike
(ma/ka)
4.1
1.7
8.3
2.7
1.6
-
4.6
6.0
-
_
1.3
6.8
4.2
4.6
2.4
3.2
4.6
2.1
—
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
Average
Recovery
Efo/\
' *
61.0
94.2
0
93.4
88.5
*
88.7
61.7
*
_
89.2
83.0
91.0
85.1
98.9
97.4
109.6
97.4
*
S(R)
*
0.2
0.8
1.5
0.3
0.8
*
1.5
20.4
*
_
0.4
10.0
6.0
0.4
0.9
0.7
0.7
1.1
*
RPD
0.9
1.5
10.0
0.9
0.5
—
4.6
5.4
_
1.0
4.5
18.0
1.1
2.4
2.0
1.8
2.5
Standard deviation of percent recovery.
Relative percent
difference
betw
een duplicate
spike dete
rminat
ions.
Sample concentration below established method detection limit.
Spike concentration <10% of sample background concentration.
Not determined.
Equivalent.
200.8-51
Revision 5.4 May 1994
-------
TABLE 11 : PRIMARY DRINKING WATER CONTAMINANTS
PRECISION AND RECOVERY DATA
ANALYTE
REGIONAL SAMPLE
BACKGROUND CONCENTRATION, /ig/L
(IV) (VI) (X)
AVERAGE MEAN1
% RECOVERY S(R)
Antimony
Arsenic
Barium
Beryl 1 i urn
Cadmi urn
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Thallium
0.16
< MDL
4.6
< MDL
0.05
0.71
208
1.2
< MDL
1.7
< MDL
< MDL
0.07
2.4
280
< MDL
0.05
5.1
130
1.2
0.23
3.6
4.3
0.01
0.03
1.0
14.3
< MDL
0.03
0.10
14.3
2.5
< MDL
0.52
< MDL
< MDL
114%
93
(*)
100%
81
94
(*)
91
86
101%
98
100
1.9
8.5
-
8.2
4.0
2.5
2.6
11.4
11.5
8.4
1.4
The three regional waters were fortified with 1.0 /ig/L of all analytes
listed, except selenium, which was fortified to 20
(*) Recovery of barium and copper was not calculated because the analyte
addition was < 20% the sample background concentration in all waters.
(Recovery calculations are not required if the concentration of the
analyte added is less than 30% of the sample background concentration.
Sect. 9. 4. 3)
S(R) Standard deviation of the mean percent recoveries.
200.8-52
Revision 5.4 May 1994
-------
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200.8-56
-------
TABLE 13: BACKGROUND AND SPIKE MEASUREMENTS IN WASTEWATER DIGESTATE'
Background
Concentrate 1
Std
Cone. Dev Spike
fjg/L //g/L fjg/L
Be
Al
Cr
V
Mn
Co
Ni
Cu
Zn
As
Se
Mo
Ag
Cd
Sb
Ba
Tl
Pb
Th
U
0.0
78.2
19.5
1,9
296.6
2.5
47.3
77.4
77.4
0.8
4.5
166.1
0.6
2.7
3.3
68.6
0.1
6.9
0.1
0.4
0.0
12.4
8.1
2.8
24.7
0.4
5.0
13.2
4.9
1.1
6.2
9.4
0.7
1.1
0.2
3.3
0.1
0.5
0.1
0.2
100
200
200
250
125
125
125
125
200
200
250
100
200
125
100
250
100
125
125
125
Std
Found Dev
jjQ/L ualL
94.5 11.8
260.9 41.2
222.2 23.3
271.8 36.5
419.0 35.7
124.7 12.3
161.7 4.9
194.5 29.5
257.4 16.3
194.9 8.0
236.8 14.2
269.8 19.0
176.0 14.6
117.0 4,8
100.2 4.8
321.0 19.4
103.3 8.0
135.1 7.8
140.2 19.5
141.2 19.3
%Rec
_&_
94.5
91.4
101.4
108.0
97.9
97.8
91.5
93.7
90.0
97.1
92.9
103.7
87.7
91.4
96.9
10.1.0
103.2
102.6
112.1
112.6
RSD Spike
% x/g/L
12.5
15.8
10.5
13.4
8.5
9.9
3.0
15.2
6.3
4.1
6.0
7.0
8.3
4.1
4.8
6.0
7.7
5.8
13.9
13.7
125
250
250
200
100
101
100
100
250
250
200
125
250
100
125
200
125
100
100
100
Concentrate 2
Found
f/g/L
118.1
309.1
274.3
219.3
397.4
100.7
142.7
172.3
302.5
244.7
194.3
302.0
214.6
96.6
125.9
279.3
129.2
110.3
113.3
113.6
Std
Dev
i/g/L
14.7
48.5
26.6
30.1
34.8
9.4
5.6
26.6
21.1
12.8
9.3
18.0
17.8
3.2
4.3
17.2
8.9
6.3
15.4
16.0
%Rec
_2L
94.5
92.4
101.9
108.7
100.8
97.2
95.4
94.9
90.0
97.6
94.9
108.7
85.6
93.9
98.1
105.4
103.3
103.4
113.2
113.2
RSD
_2L
12.4
15.7
9.7
13.7
8.8
9.3
3.9
15.4
7.0
5.2
4.8
6.0
8.3
3.3
3.4
6.2
6.9
5.7
13.6
14.1
RSDr
_2k_
3.5
2.7
2.0
2.6
1.0
2.8
2.1
2.2
1.8
3.4
3.8
1.5
2.3
2.9
1.8
2.5
2.1
1.8
2.7
2.5
8 Results from 10 participating laboratories. Wastewater digestate supplied with the study
materials. Mean background concentrations determined by the participants.
200.8-57 Revision 5.4 May 1994
-------
TABLE 14: SPIKE MEASUREMENTS IN PARTICIPANT'S WASTEWATER'
Concentrate 1
Be
Al
Cr
V
Mn
Co
N:
Cu
Zn
As
Se
Mo
Ag
Cd
Sb
Ba
Tl
Pb
Th
U
Spike
ilSlL
101
200
200
250
125
125
125
125
200
200
250
100
200
125
100
250
100
125
125
125
Found
ualL
103.4
198.7
205.4
246.5
119.0
125.8
127.4
126.8
201.4
207.3
256.8
98.6
200.7
123.2
92.2
245.2
100.0
125.8
124.2
130.4
Std Dev
j/g/L
12.0
23.9
12.3
4.4
5.4
7.0
9.7
5.3
36.7
11.9
26.4
4.6
48.9
11.5
4.4
12.8
0.9
5.1
7.6
10.3
%Rec
_2L
103.4
99.4
102.7
98.6
95.2
100.6
101.9
101.4
100.7
103.7
102.7
98.6
100.4
98.6
92.2
98.1
100.0
100.6
99.4
104.3
RSD
_%_
11.6
12.0
6.0
1.8
4.5
5.6
7.6
4.2
18.2
5.7
10.3
4.7
24.4
9.3
4.8
5.2
0.9
4.1
6.1
7.9
Spike
ua/L
125
250
250
200
100
101
100
100
250
250
200
125
250
100
125
200
125
100
100
100
Found
ua/L
128.2
252.4
253.4
196.8
95.5
99.5
101.0
105.3
246.4
263.0
214.
123.2
231.2
95.8
119.0
204.7
128.0
100.8
99.8
106.4
-•**-•+*• "^^« •*.'
Std Dev
ua/L
13.6
15.5
15.4
2.8
4.3
5.3
7.5
3.6
29.7
2.6
18.7
6.7
63.5
2.9
1.0
12.1
6.0
2.7
'5.7
6.8
%Rec
_5L
102.6
101.0
101.4
98.4
95.5
98.5
101.0
105.3
98.6
105.2
107.3
98.6
92.5
95.8
95.2
102.4
102.4
100.8
99.8
106.4
RSD
_5L
10.6
6.1
6.1
1.4
4.5
5.3
7.4
3.4
12.1
1.0
8.7
5.4
27.5
3.0
0.8
5.9
4.7
2.7
5.7
6.4
RSDr
_2L
2.4
2.9
1.1
2.0
0.8
1.8
1.7
2.8
2.6
3.2
3.6
2.2
8.2
5.8
2.8
2.1
3.5
2.2
3.2
2.3
"Results from 5 participating laboratories. Mean concentrations before spiking are not listed
because they varied considerably among the different wastewaters.
200.8-58
Revision 5.4 May 1994
-------
METHOD 200.9
DETERMINATION OF TRACE ELEMENTS BY STABILIZED TEMPERATURE
GRAPHITE FURNACE ATOMIC ABSORPTION
Revision 2.2
EMMC Version
J.T. Creed, T.D. Martin, L.B. Lobring, and J.W. O'Dell - Method 200.9,
Revision 1.2 (1991)
J.T. Creed, T.D. Martin, and J.W. O'Dell - Method 200.9, Revision 2.2 (1994)
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
200.9-1
-------
METHOD 200.9
DETERMINATION OF TRACE ELEMENTS BY STABILIZED TEMPERATURE
GRAPHITE FURNACE ATOMIC ABSORPTION
1.0 SCOPE AND APPLICATION
1.1 This method1 provides procedures for the determination of dissolved
and total recoverable elements by graphite furnace atomic absorption
(GFAA) in ground water, surface water, drinking water, storm runoff,
industrial and domestic wastewater. This method is also applicable
to the determination of total recoverable elements in sediment,
sludges, and soil. This method is applicable to the following
analytes:
Chemical Abstract Services
Analyte Registry Numbers (CASRN)
Aluminum
Antimony
Arsenic
Beryl 1 i urn
Cadmium
Chromium
Cobalt
Copper
Iron
Lead
Manganese
Nickel
Selenium
Silver
Thallium
Tin
(A!)
(Sb)
(As)
(Be)
(Cd)
(Cr)
(Co)
(Cu)
(Fe)
(Pb)
(Mn)
(Ni)
(Se)
(Ag)
(Tl)
(Sn)
7429-90-5
7440-36-0
7440-38-2
7440-41-7
7440-43-9
7440-47-3
7440-48-4
7440-50-8
7439-89-6
7439-92-1
7439-96-5
7440-02-0
7782-49-2
7440-22-4
7440-28-0
7440-31-5
1.2 For reference where this method is approved for use in compliance
monitoring programs [e.g., Clean Water Act (NPDES) or Safe Drinking
Water Act (SDWA)] consult both the appropriate sections of the Code
of Federal Regulation (40 CFR Part 136 Table IB for NPDES, and Part
141 § 141.23 for drinking water), and the latest Federal Register
announcements.
1.3 Dissolved analytes can be determined in aqueous samples after
suitable filtration and acid preservation.
1.4 With the exception of silver, where this method is approved for the
determination of certain metal and metalloid contaminants in
drinking water, samples may be analyzed by direct injection into the
furnace without acid digestion if the sample has been properly
200.9-2 Revision 2.2 May 1994
-------
preserved with acid, has turbidity of < 1 NTU at the time of
analysis, and is analyzed using the appropriate method matrix
modifiers. This total recoverable determination procedure is
referred to as "direct analysis". However, in the determination of
some primary drinking water metal contaminants, such as arsenic and
thallium preconcentration of the sample may be required prior to
analysis in order to meet drinking water acceptance performance
criteria (Sect. 10.5).
1.5 For the determination of total recoverable analytes in aqueous and
solid samples a digestion/extraction is required prior to analysis
when the elements are not in solution (e.g., soils, sludges,
sediments and aqueous samples that may contain particulate and
suspended solids). Aqueous samples containing suspended or
particulate material > 1% (w/v) should be extracted as a solid type
sample.
1.6 Silver is only slightly soluble is the presence of chloride unless
there is a sufficient chloride concentration to form the soluble
chloride complex. Therefore, low recoveries of silver may occur in
samples, fortified sample matrices and even fortified blanks if
determined as a dissolved analyte or by "direct analysis" where the
sample has not been processed using the total recoverable digestion.
For this reason it is recommended that samples be digested prior to
the determination of silver. The total recoverable sample digestion
procedure given in this method is suitable for the determination of
silver in aqueous samples containing concentrations up to 0.1 mg/L.
For the analysis of wastewater samples containing higher
concentrations of silver, succeeding smaller volume, well mixed
aliquots should be prepared until the analysis solution contains
< 0.1 mg/L silver. The extraction of solid samples containing
concentrations of silver > 50 mg/kg should be treated in a similar
manner.
1.7 Method detection limits and instrument operating conditions for the
applicable elements are listed in Table 2. These are intended as a
guide and are typical of a system optimized for the element
employing commercial instrumentation. However, actual method
detection limits and linear working ranges will be dependent on the
sample matrix, instrumentation and selected operating conditions.
1.8 The sensitivity and limited linear dynamic range (LDR) of 6FAA often
implies the need to dilute a sample prior to analysis. The actual
magnitude of the dilution as well as the cleanliness of the labware
used to perform the dilution can dramatically influence the quality
of the analytical results. Therefore, samples types requiring large
dilutions (>50:1) should be analyzed by an another approved test
procedure which has a larger LDR or which is inherently less
sensitive than GFAA.
1.9 Users of the method data should state the data-quality objectives
prior to analysis. Users of the method must document and have on
file the required initial demonstration performance data described
in Section 9.2 prior to using the method for analysis.
200.9-3 Revision 2.2 May 1994
-------
2.0 SUMMARY OF METHOD
2.1 An aliquot of a well mixed, homogeneous aqueous or solid sample is
accurately weighed or measured for sample processing. For total
recoverable analysis of a solid or an aqueous sample containing
undissolved material, analytes are first solubilized by gentle
refluxing with nitric and hydrochloric acids. After cooling, the
sample is made up to volume, is mixed and centrifuged or allowed to
settle overnight prior to analysis. For the determination of
dissolved analytes in a filtered aqueous sample aliquot, or for the
"direct analysis" total recoverable determination of analytes where
sample turbidity is < 1 NTU, the sample is made ready for analysis
by the appropriate addition of nitric acid, and then diluted to a
predetermined volume and mixed before analysis.
2.2 The analytes listed in this method are determined by stabilized
temperature platform graphite furnace atomic absorption (STPGFAA).
In STPGFAA, the sample and the matrix modifier are first pipetted
onto the platform or a device which provides delayed atomization.
The furnace chamber is then purged with a continuous flow of a
premixed gas (95% argon - 5% hydrogen) and the sample is dried at a
relatively low temperature (about 120°C) to avoid spattering. Once
dried, the sample is pretreated in a char or ashing step which is
designed to minimize the interference effects caused by the
concomitant sample matrix. After the char step the furnace is
allowed to cool prior to atomization. The atomization cycle is
characterized by rapid heating of the furnace to a temperature where
the metal (analyte) is atomized from the pyrolytic graphite surface
into a stopped gas flow atmosphere of argon containing 5% hydrogen.
(Only selenium is determined in an atmosphere of high purity argon.)
The resulting atomic cloud absorbs the element specific atomic
emission produced by a hollow cathode lamp (HCL) or an electrode!ess
discharge lamp (EDL). Following analysis the furnace is subjected
to a cleanout period of high temperature and continuous argon flow.
Because the resulting absorbance usually has a nonspecific component
associated with the actual analyte absorbance, an instrumental
background correction device is required to subtract from the total
signal the component which is nonspecific to the analyte. In the
absence of interferences, the background corrected absorbance is
directly related to the concentration of the analyte. Interferences
relating to STPGFAA (Section 4.0) must be recognized and corrected.
Suppressions or enhancements of instrument response caused by the
sample matrix must be corrected by the method of standard addition
(Section 11.5).
3.0 DEFINITIONS
3.1 Calibration Blank - A volume of reagent water acidified with the
same acid matrix as in the calibration standards. The calibration
blank is a zero standard and is used to auto-zero the AA instrument
(Sect. 7.10.1).
3.2 Calibration Standard (CAL) - A solution prepared from the dilution
of stock standard solutions. The CAL solutions are used to
200.9-4 Revision 2.2 May 1994
-------
calibrate the instrument response with respect to analyte
concentration (Sect. 7.9). jr"
3.3 Dissolved Analyte - The concentration of analyte in an aqueous
sample that will pass through a 0.45-/zm membrane filter assembly
prior to sample acidification (Sect. 11.1).
3.4 Field Reagent Blank (FRB) - An aliquot of reagent water or other
blank matrix that is placed in a sample container in the laboratory
and treated as a sample in all respects, including shipment to the
sampling site, exposure to the sampling site conditions, storage,
preservation, and all analytical procedures. The purpose of the FRB
is to determine if method analytes or other interferences are
present in the field environment (Sect 8.5).
3.5 Instrument Detection Limit (IDL) -.The concentration equivalent to
the analyte signal which is equal to three times the standard
deviation of a series of ten replicate measurements of the
calibration blank signal at the same wavelength.
3.6 Instrument Performance Check (IPC) Solution - A solution of method
analytes, used to evaluate the performance of the instrument system
with respect to a defined set of method criteria (Sects. 7.11 &
9.3.4).
3.7 Laboratory Duplicates (LD1 and LD2) - Two aliquots of the same
sample taken in the laboratory and analyzed separately with
identical procedures. Analyses of LD1 and LD2 indicates precision
associated with laboratory procedures, but not with sample
collection, preservation, or storage procedures.
3.8 Laboratory Fortified Blank (LFB) - An aliquot of LRB to which known
quantities of the method analytes are added in the laboratory. The
LFB is analyzed exactly like a sample, and its purpose is to
determine whether the methodology is in control and whether the
laboratory is capable of making accurate and precise measurements
(Sects. 7.10.3 & 9.3.2).
3.9 Laboratory Fortified Sample Matrix (LFM) - An aliquot of an
environmental sample to which known quantities of the method
analytes are added in the laboratory. The LFM is analyzed exactly
like a sample, and its purpose is to determine whether the sample
matrix contributes bias to the analytical results. The background
concentrations of the analytes in the sample matrix must be
determined in a separate aliquot and the measured values in the LFM
corrected for background concentrations (Sect. 9.4).
3.10 Laboratory Reagent Blank (LRB) - An aliquot of reagent water or
other blank matrices that are treated exactly as a sample including
exposure to all glassware, equipment, solvents, reagents, and
internal standards that are used with other samples. The LRB is
used to determine if method analytes or other interferences are
present in the laboratory environment, reagents, or apparatus
(Sects. 7.10.2 & 9.3.1).
200.9-5 Revision 2.2 May 1994
-------
3.11 Linear Dynamic Range (LDR) - The concentration range over which the
instrument response to an analyte is linear (Sect. 9.2.2).
3.12 Matrix Modifier - A substance added to the graphite furnace along
with the sample in order to minimize the interference effects by
selective volatilization of either analyte or matrix components.
3.13 Method Detection Limit (MDL) - The minimum concentration of an
analyte that can be identified, measured, and reported with 99%
confidence that the analyte concentration is greater than zero
(Sect. 9.2.4 and Table 2).
3.14 Quality Control Sample (QCS) - A solution of method analytes of
known concentrations which is used to fortify an aliquot of LRB or
sample matrix. The QCS is obtained from a source external to the
laboratory and different from the source of calibration standards.
It is used to check either laboratory or instrument performance
(Sects. 7.12 & 9.2.3).
3.15 Solid Sample - For the purpose of this method, a sample taken from
material classified as either soil, sediment or sludge.
3.16 Standard Addition - The addition of a known amount of analyte to the
sample in order to determine the relative response of the detector
to an analyte within the sample matrix. The relative response is
then used to assess either an operative matrix effect or the sample
analyte concentration (Sects. 9.5.1 & 11.5).
3.17 Stock Standard Solution - A concentrated solution containing one or
more method analytes prepared in the laboratory using assayed
reference materials or purchased from a reputable commercial source
(Sect. 7.8).
3.18 Total Recoverable Analyte - The concentration of analyte determined
to be in either a solid sample or an unfiltered aqueous sample
following treatment by refluxing with hot dilute mineral acid(s) as
specified in the method (Sects. 11.2 & 11.3).
3.19 Water Sample - For the purpose of this method, a sample taken from
one of the following sources: drinking, surface, ground, storm
runoff, industrial or domestic wastewater.
4.0 INTERFERENCES
4.1 Several interference sources may cause inaccuracies in the
determination of trace elements by GFAA. These interferences can be
classified into three major subdivisions, namely spectral, matrix,
and memory.
4.2 Spectral interferences are caused by the resulting absorbance of
light by a molecule or atom which is not the analyte of interest or
emission from black body radiation.
4.2.1 Spectral interferences caused by an element only occur if
200.9-6 Revision 2.2 May 1994
-------
there is a spectral overlap between the wavelength of the
interfering element and the analyte of interest. Fortunately,
this type of interference is relatively uncommon in STPGFAA
because of the narrow atomic line widths associated with
STPGFAA. In addition, the use of appropriate furnace
temperature programs and high spectral purity lamps as light
sources can minimize the possibility of this type of
interference. However, molecular absorbances can span several
hundred nanometers producing broadband spectral interferences.
This type of interference is far more common in STPGFAA. The
use of matrix modifiers, selective volatilization, and
background correctors are all attempts to eliminate unwanted
nonspecific absorbance. The nonspecific component of the
total absorbance can vary considerably from sample type to
sample type. Therefore, the effectiveness of a particular
background correction device may vary depending on the actual
analyte wavelength used as well as the nature and magnitude of
the interference. The background correction device to be used
with this method is not specified, however, it must provide an
analytical condition that is not subject to the occurring
interelement spectral interferences of palladium on copper,
iron on selenium, and aluminum on arsenic.
4.2.2 Spectral interferences are also caused by the emissions from
black body radiation produced during the atomization furnace
cycle. This black body emission reaches the photomultiplier
tube, producing erroneous results. The magnitude of this
interference can be minimized by proper furnace tube alignment
and monochromator design. In addition, atomization
temperatures which adequately volatilize the analyte of
interest without producing unnecessary black body radiation
can help reduce unwanted background emission during analysis.
4.3 Matrix interferences are caused by sample components which inhibit
the formation of free atomic analyte atoms during the atomization
cycle.
->
4.3.1 Matrix interferences can be of a chemical or physical nature.
In this method the use of a delayed atomization device which
provides stabilized temperatures is required. These devices
provide an environment which is more conducive to the
formation of free analyte atoms and thereby minimize this type
of interference. This type of interference can be detected by
analyzing the sample plus a sample aliquot fortified with a
k/iown concentration of the analyte. If the determined
concentration of the analyte addition is outside a designated
range, a possible matrix effect should be suspected (Sect.
y * T" • *3 j •
4.3.2 The use of nitric acid is preferred for GFAA analyses in order
to minimize vapor state anionic chemical interferences,
however, in this method hydrochloric acid is required to
maintain stability in solutions containing antimony and
silver. When hydrochloric acid is used, the chloride ion
200.9-7 Revision 2.2 May 1994
-------
vapor state interferences must be reduced using an appropriate
matrix modifier. In this method a combination modifier of
palladium, magnesium nitrate and a hydrogen(5%)-argon(95%) gas
mixture is used for this purpose. The effects and benefits of
using this modifier are discussed in detail in reference 2. of
Section 16.0. Listed in Section 4.4 are some typical observed
effects when using this modifier.
4.4 Specific Element Interferences
Antimony: Antimony suffers from an interference produced by
K2S04.3 In the absence of hydrogen in the char cycle (1300°C),
K2S04 produces a relatively high (1.2 abs) background
absorbance which can produce a false signal, even with Zeeman
background correction. However, this background level can be
dramatically reduced (0.1 abs) by the use of a hydrogen/argon
gas mixture in the char step. This reduction in background is
strongly influenced by the temperature of the char step.
NOTE: The actual furnace temperature may vary from instrument
to instrument. Therefore, the actual furnace
temperataure should be determined on an individual
basis.
Aluminum: The palladium matrix modifier may have elevated
levels of Al which will cause elevated blank absorbances.
Arsenic: The HC1 present from the digestion procedure can
influence the sensitivity for As. 20 //,L of a 1% HC1 solution
with Pd used as a modifier results in a 20% loss in
sensitivity relative to the analyte in a 1% HN03 solution.
Unfortunately, the use of Pd/Mg/H? as a modifier does not
significantly reduce this suppression, and therefore, it is
imperative that each sample and calibration standard alike
contain the same HC1 concentration.2
Cadmium: The HC1 present from the digestion procedure can
influence the sensitivity for Cd. 20 //,L of a 1% HC1 solution
with Pd used as a modifier results in a 80% loss in
sensitivity relative to the analyte in a' 1% HN03 solution.
The use of Pd/Mg/H2 as a matrix modifier reduces this
suppression to less than 10%.2
Lead: The HC1 present from the digestion procedure can
influence the sensitivity for Pb. 20 ill of a 1% HC1 solution
with Pd used as a modifier results in a 75% loss in
sensitivity relative to the analyte response in a 1% HN03
solution. The use of Pd/Mg/H2 as a matrix modifier reduces
this suppression to less than 10%.
Selenium: Iron has been shown to suppress Se response with
continuum background correction.3 In addition, the use of
hydrogen as a purge gas during the dry and char steps can
cause a suppression in Se response if not purged from the
200.9-8 Revision 2.2 May 1994
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furnace prior to atomization.
Silver: The palladium used in the modifier preparation may
have elevated levels of Ag which will cause elevated blank
absorbances.
Thallium: The HC1 present from the digestion procedure can
influence the sensitivity for Tl. 20 /iL of a 1% HC1 solution
with Pd used as a modifier results in a 90% loss in
sensitivity relative to the analyte in a 1% HN03 solution.
The use of Pd/Mg/H2 as a matrix modifier reduces this
suppression to less than 10%.
4.5 Memory interferences result from analyzing a sample containing a
high concentration of an element (typically a high atomization
temperature element) which cannot be removed quantitatively in one
complete set of furnace steps. The analyte which remains in the
furnace can produce false positive signals on subsequent sample(s).
Therefore, the analyst should establish the analyte concentration
which can be injected into the furnace and adequately removed in one
complete set of furnace cycles. If this concentration is exceeded,
the sample should be diluted and a blank analyzed to assure the
memory effect has been eliminated before reanalyzing the diluted
sample.
5.0 SAFETY
5.1 The toxicity or carcinogenicity of each reagent used in this method
have not been fully established. Each chemical should be regarded
as a potential health hazard and exposure to these compounds should
be as low as reasonably achievable. Each laboratory is responsible
for maintaining a current awareness file of OSHA regulations
regarding, the safe handling of the chemicals specified in this
method. " A reference file of material data handling sheets should
also be made available to all personnel involved in the chemical
analysis. Specifically, concentrated nitric and hydrochloric acids
present various hazards and are moderately toxic and extremely
irritating to skin and mucus membranes. Use these reagents in a
fume hood whenever possible and if eye or skin contact occurs, flush
with large volumes of water. Always wear safety glasses or a shield
for eye protection, protective clothing and observe proper mixing
when working with these reagents.
5.2 The acidification of samples containing reactive materials may
result in the release of toxic gases, such as cyanides or sulfides.
Acidification of samples should be done in a fume hood.
5.3 All personnel handling environmental samples known to contain or to
have been in contact with human waste should be immunized against
known disease causative agents.
5.4 The graphite tube during atomization emits intense UV radiation.
Suitable precautions should be taken to protect personnel from such
a hazard.
200.9-9 Revision 2.2 May 1994
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5.5 The use of the argon/hydrogen gas mixture during the dry and char
steps may evolve a considerable amount of HC1 gas. Therefore,
adequate ventilation is required.
5.6 It is the responsibility of the user of this method to comply with
relevant disposal and waste regulations. For guidance see Sections
14.0 and 15.0.
6.0 EQUIPMENT AND SUPPLIES
6.1 Graphite Furnace Atomic Absorbance Spectrophotometer
6.1.1 The 6FAA spectrometer must be capable of programmed heating of
the graphite tube and the associated delayed atomization
device. The instrument must be equipped with an adequate
background correction device capable of removing undesirable
non-specific absorbance over the spectral region of interest
and provide an analytical condition not subject to the
occurrence of interelement spectral overlap interferences.
The furnace device must be capable of utilizing an alternate
gas supply during specified cycles of the analysis. The
capability to record relatively fast (< 1 s) transient signals
and evaluate data on a peak area basis is preferred. In
addition, a recirculating refrigeration bath is recommended
for improved reproducibility of furnace temperatures.
6.1.2 Single element hollow cathode lamps or single element
electrode!ess discharge lamps along with the associated power
supplies.
6.1.3 Argon gas supply (high-purity grade, 99.99%) for use during
the atomization of selenium, for sheathing the furnace tube
when in operation, and during furnace cleanout.
6.1.4 Alternate gas mixture (hydrogen 5% - argon 95%) for use as a
continuous gas flow environment during the dry and char
furnace cycles.
6.1.5 Autosampler capable of adding matrix modifier solutions to the
furnace, a single addition of analyte, and completing methods
of standard additions when required.
6.2 Analytical balance, with capability to measure to 0.1 rug, for use in
weighing solids, for preparing standards, and for determining
dissolved solids in digests or extracts.
6.3 A temperature adjustable hot plate capable of maintaining a
temperature of 95°C.
6.4 (optional) A temperature adjustable block; digester capable of
maintaining a temperature of 95°C and equipped with 250-mL
constricted digestion tubes.
200.9-10 Revision 2.2 May 1994
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6.5 (optional) A steel cabinet centrifuge with guard bowl, electric
timer and brake.
6.6 A gravity convection drying oven with thermostatic control capable
of maintaining 180°C ± 5°C.
6.7 (optional) An air displacement pipetter capable of delivering
volumes ranging from 100 to 2500 #L with an assortment of high
quality disposable pipet tips.
6.8 Mortar and pestle, ceramic or nonmetallic material.
6.9 Polypropylene sieve, 5-mesh (4 mm opening).
6.10 Labware - All reusable labware (glass, quartz, polyethylene, PTFE,
FEP, etc.) should be sufficiently clean for the task objectives.
Several procedures found to provide clean labware include washing
with a detergent solution, rinsing with tap water, soaking for 4 h
or more in 20% (v/v) nitric acid or a mixture of dilute HN03 and HC1
(1+2+9), rinsing with reagent water and storing clean.1 Ideally,
ground glass surfaces should be avoided to eliminate a potential
source of random contamination. When this is impractical,
particular attention should be given to all ground glass surfaces
during cleaning. Chromic acid cleaning solutions must be avoided
because chromium is an analyte.
6.10.1 Glassware - Volumetric flasks, graduated cylinders,
funnels and centrifuge tubes (glass and /or metal-free
plastic).
6.10.2 Assorted calibrated pipettes.
6.10.3 Conical Phillips beakers, 250-mL with 50-mm watch
glasses.
6.10.4 Griffin beakers, 250-mL with 75-mm watch glasses and
(optional) 75-mm ribbed watch glasses.
6.10.5 (optional) PTFE and/or quartz Griffin beakers, 250-mL
with PTFE covers.
6.10.6 Evaporating dishes or high-form crucibles, porcelain,
100 tnL capacity.
6.10.7 Narrow-mouth storage bottles, FEP (fluorinated ethylene
propylene) with screw closure, 125-mL to 1-L capacities.
6.10.8 One-piece stem FEP wash bottle with screw closure, 125-
mL capacity.
7.0 REAGENTS AND STANDARDS
7.1 Reagents may contain elemental impurities which might affect
analytical data. Only high-purity reagents that conform to the
200.9-11 Revision 2.2 May 1994
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American Chemical Society specifications8 should be used whenever
possible. If the purity of a reagent as in question, analyze for
contamination. All acids used for this method must be of ultra
high-purity grade or equivalent. Suitable acids are available from
a number of manufacturers. Redistilled acids prepared by sub-
boiling distillation are acceptable.
7.2 Hydrochloric acid, concentrated (sp.gr. 1.19) - HC1.
7.2.1 Hydrochloric acid (1+1) - Add 500 ml concentrated HC1 to 400
ml reagent water and dilute to 1 L.
7.2.2 Hydrochloric acid (1+4) - Add 200 ml concentrated HC1 to 400
ml reagent water and dilute to 1 L.
7.3 Nitric acid, concentrated (sp.gr. 1.41) - HN03.
7.3.1 Nitric acid (1+1) - Add 500 ml concentrated HN03 to 400 ml
reagent water and dilute to 1 L.
7.3.2 Nitric acid (1+5) - Add 50 ml concentrated HN03 to 250 ml
reagent water.
7.3.3 Nitric acid (1+9) - Add 10 ml concentrated HN03 to 90 ml
reagent water.
7.4 Reagent water. All references to water in this method refer to ASTM
Type I grade water.9
7.5 Ammonium hydroxide, concentrated (sp. gr. 0.902).
7.6 Tartaric acid, ACS reagent grade.
7.7 Matrix Modifier, dissolve 300 mg palladium (Pd) powder in cone. HN03
(1 mL of HN03, adding 0.1 ml of concentrated HC1 if necessary).
Dissolve 200 mg of Mg(N03)2 in ASTM Type I water. Pour the two
solutions together and dilute to 100 ml with ASTM Type I water.
NOTE: It is recommended that the matrix modifier be analyzed
separately in order to assess the contribution of the modifier
to the absorbance of calibration and reagent blank solutions.
7.8 Standard stock solutions may be purchased or prepared from ultra-
high purity grade chemicals (99.99 to 99.999% pure). All compounds
must be dried for 1 h at 105°C, unless otherwise specified. It is
recommended that stock solutions be stored in FEP bottles. Replace
stock standards when succeeding dilutions for preparation of
calibration standards can not be verified.
CAUTION: Many of these chemicals are extremely toxic if inhaled
or swallowed (Sect. 5.1). Wash hands thoroughly after
handling.
200.9-12 Revision 2.2 May 1994
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Typical stock solution preparation procedures follow for 1-L
quantities, but for the purpose of pollution prevention, the analyst
is encouraged to prepare smaller quantities when possible.
Concentrations are calculated based upon the weight of the pure
element or upon the weight of the compound multiplied by the
fraction of the analyte in the compound.
From pure element,
weight (mg)
Concentration =
volume (L)
From pure compound,
weight (mg) x gravimetric factor
Concentration =
volume (L)
where:
gravimetric factor = the weight fraction of the analyte in
the compound.
7.8.1 Aluminum solution, stock, 1 ml = 1000 /ig Al: Dissolve 1.000 g
of aluminum metal, weighed accurately to at least four
significant figures, in an acid mixture of 4.0 ml of (1+1) HC1
and 1.0 ml of concentrated HN03 in a beaker. Warm beaker
slowly to effect solution. When dissolution is complete,
transfer solution quantitatively to a 1-L flask, add an
additional 10.0 mL of (1+1) HC1 and dilute to volume with
reagent water.
7.8.2 Antimony solution, stock, 1 ml = 1000 /zg Sb: Dissolve 1.000
g of antimony powder, weighed accurately to at least four
significant figures, in 20.0 ml (1+1) HNO, and 10.0 ml
concentrated HC1. Add 100 ml reagent water and 1.50 g
tartaric acid. Warm solution slightly to effect complete
dissolution. Cool solution and add reagent water to volume in
a 1-L volumetric flask.
7.8.3 Arsenic solution, stock, 1 mL = 1000 /jg As: Dissolve 1.320 g
of As203 (As fraction = 0.7574), weighed accurately to at
least four significant figures, in 100 mL of reagent water
containing 10.0 mL concentrated NH4OH. Warm the solution
gently to effect dissolution. Acidify the solution with 20.0
mL concentrated HN03 and dilute to volume in a 1-L volumetric
flask with reagent water.
7.8.4 Beryllium solution, stock, 1 mL = 1000 //g Be: DO NOT DRY
Dissolve 19.66 g BeS04»4H20 (Be fraction = 0.0509), weighed
accurately to at least four significant figures, in reagent
200.9-13 Revision 2.2 May 1994
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water, add 10.0 ml concentrated HN03, arid dilute to volume in
a 1-L volumetric flask with reagent water.
7.8.5 Cadmium solution, stock, 1 ml = 1000 M9 Cd: Dissolve 1.000 g
Cd metal, acid cleaned with (1+9) HN03, weighed accurately to
at least four significant figures, in 50 ml (1+1) HNO, with
heating to effect dissolution. Let solution cool and dilute
with reagent water in a 1-L volumetric flask.
7.8.6 Chromium solution, stock, 1 mL = 1000 M9 Cr: Dissolve 1.923
g CrO, (Cr fraction = 0.5200), weighed accurately to at least
four significant figures, in 120 mL (1+5) HN03. When solution
is complete, dilute to volume in a 1-L volumetric flask with
reagent water.
7 8.7 Cobalt solution, stock, 1 mL = 1000 /tg Co: Dissolve 1.000 g
Co metal, acid cleaned with (1+9) HN03, weighed accurately to
at least four significant figures, in 50.0 mL (1+1) HN03. Let
solution cool and dilute to volume in a 1-L volumetric flask
with reagent water.
7 8.8 Copper solution, stock, 1 mL = 1000 /ig Cu: Dissolve 1.000 g Cu
metal, acid cleaned with (1+9) HN03, weighed accurately to at
least four significant figures, in 50.0 mL (1+1) HN03 with
heating to effect dissolution. Let solution cool and dilute
in a 1-L volumetric flask with reagent water.
7.8.9 Iron solution, stock, 1 mL = 1000 jug Fe: Dissolve 1.000 g Fe
metal, acid cleaned with (1+1) HC1, weighed accurately to four
significant figures, in 100 mL (1+1) HC1 with heating to
effect dissolution. Let solution cool and dilute with reagent
water in a 1-L volumetric flask.
7.8.10 Lead solution, stock, 1 mL = 1000 fig Pb: Dissolve 1.599 g
Pb(NO,)2 (Pb fraction = 0.6256), weighed accurately to at
least four significant figures, in a minimum amount of (1+1)
HN03. Add 20.0 mL (1+1) HN03 and dilute to volume in a 1-L
volumetric flask with reagent water.
7.8.11 Manganese solution, stock, 1 mL = 1000 M9 Mn: Dissolve 1.000
g of manganese metal, weighed accurately to at least four
significant figures, in 50 mL (1+1) HN03 and dilute to volume
in a 1-L volumetric flask with reagent water.
7.8.12 Nickel solution, stock, 1 mL = 1000 pg Ni: Dissolve 1.000 g
of nickel metal, weighed accurately to at least four
significant figures, in 20.0 mL hot concentrated HN03, cool,
and dilute to volume in a 1-L volumetric flask with reagent
water.
7.8.13 Selenium solution, stock, 1 mL = 1000 /jg Se: Dissolve 1.405
g SeO, (Se fraction = 0.7116), weighed accurately to at least
four significant figures, in 200 mL reagent water and dilute
to volume in a 1-L volumetric flask with reagent water.
200.9-14 Revision 2.2 May 1994
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7.8.14 Silver solution, stock, 1 ml = 1000 /ig Ag: Dissolve 1.000 g
Ag metal, weighed accurately to at least four significant
figures, in 80 ml (1+1) HN03 with heating to effect
dissolution. Let solution cool and dilute with reagent water
in a 1-L volumetric flask. Store solution in amber bottle or
wrap bottle completely with aluminum foil to protect solution
from light.
7.8.15 Thallium solution, stock, 1 ml = 1000 /jg Tl: Dissolve 1.303 g
T1N03 (Tl fraction = 0.7672), weighed accurately to at least
four significant figures, in reagent water. Add 10.0 ml
concentrated HN03 and dilute to volume in a 1-L volumetric
flask with reagent water.
7.8.16 Tin solution, stock, 1 mL = 1000 fig Sn: Dissolve 1.000 g Sn
shot, weighed accurately to at least four significant figures
in an acid mixture of 10.0 mL concentrated HC1 and 2 0 mL
(1+1) HN03 with heating to effect dissolution. Let solution
cool, add 200 mL concentrated HC1, and dilute to volume in a
1-L volumetric flask with reagent water.
7.9 Preparation of Calibration Standards - Fresh calibration standards
(CAL Solution) should be prepared every two weeks, or as needed
Dilute each of the stock standard solutions to levels appropriate to
the operating range of the instrument using the appropriate acid
diluent (see note). The element concentrations in each CAL solution
should be sufficiently high to produce good measurement precision and
to accurately define the slope of the response curve. The instrument
calibration should be initially verified using a quality control
sample (Sections 7.12 & 9.2.3).
NOTE: The appropriate acid diluent .for the determination of
dissolved elements in water and for the "direct analysis" of
drinking water with turbidity < 1 NTU is 1% HN03. For total
recoverable elements in waters, the appropriate acid diluent
is 2% HN03 and 1% HC1, and the appropriate acid diluent for
total recoverable elements in solid samples is 2% HNO, and 2%
HC1. The reason for these different diluents is to match the
types of acids and the acid concentrations of the samples with
the acid present in the standards and blanks.
7.10 Blanks - Four types of blanks are required for this method. A
calibration blank is used to establish the analytical calibration
curve, the laboratory reagent blank (LRB) is used to assess possible
contamination from the sample preparation procedure and to assess
spectral background, the laboratory fortified blank is used to assess
routine laboratory performance, and a rinse blank is used to flush the
instrument autosampler uptake system. All diluent acids should be
made from concentrated acids (Sects. 7.2 & 7.3) and ASTM Type I water.
7.10.1 The calibration blank consists of the appropriate acid diluent
(Sect. 7.9 note) (HC1/HN03) in ASTM Type I water. The
calibration blank should be stored in a FEP bottle.
200.9-15 Revision 2.2 May 1994
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7.10.2 The laboratory reagent blank (LRB) must contain all the
reagents in the same volumes as used in processing the
samples. The LRB must be carried through the same entire
preparation scheme as the samples including sample digestion,
when applicable.
7.10.3 The laboratory fortified blank (LFB) is prepared by fortifying
an aliquot of the laboratory reagent blank with all analytes
to provide a final concentration which will produce an
absorbance of approximately 0.1 for each analyte. The LFB must
be carried through the same entire preparation scheme as the
samples including sample digestion, when applicable.
7.10.4 The rinse blank is prepared as needed by adding 1.0 mL of
CORC. HN03 and 1.0 mL cone. HC1 to 1 liter of ASTM Type I
water and stored in a convenient manner.
7.11 Instrument Performance Check (IPC) Solution - The IPC solution is used
to periodically verify instrument performance during analysis. It
should be prepared in the same acid mixture as the calibration
standards (Sect. 7.9 note) by combining method analytes at appropriate
concentrations to approximate the midpoint of the calibration curve.
The IPC solution should be prepared from the same standard stock
solutions used to prepare the calibration standards and stored in a
FEP bottle. Agency programs may specify or request that additional
instrument performance check solutions be prepared at specified
concentrations in order to meet particular program needs.
7.12 Quality Control Sample (QCS) - For initial and periodic verification
of calibration standards and instrument performance, analysis of a QCS
is required. The QCS must be obtained from an outside source
different from the standard stock solutions and prepared in the same
acid mixture as the calibration standards (Sect.7.9 note). The
concentration of the analytes in the QCS solution should be such that
the resulting solution will provide an absorbance reading of
approximately 0.1. The QCS solution should be stored in a FEP bottle
and analyzed as needed to meet data-quality needs. A fresh solution
should be prepared quarterly or more frequently as needed.
8.0 SAMPLE COLLECTION. PRESERVATION. AND STORAGE
8.1 Prior to the collection of an aqueous sample, consideration should be
given to the type of data required, (i.e., dissolved or total
recoverable), so that appropriate preservation and pretreatment steps
can be taken. The pH of all aqueous samples must be tested
immediately prior to aliquoting for processing or "direct analysis" to
ensure the sample has been properly preserved. If properly acid
preserved, the sample can be held up to 6 months before analysis.
8.2 For the determination of the dissolved elements, the sample must be
filtered through a 0.45-/jm pore diameter membrane filter at the time
of collection or as soon thereafter as practically possible. (Glass
or plastic filtering apparatus are recommended to avoid possible
contamination.) Use a portion of the filtered sample to rinse the
200.9-16 Revision 2.2 May 1994
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filter flask, discard this portion and collect the required volume of
filtrate. Acidify the filtrate with (1+1) nitric acid immediately
following filtration to pH < 2.
8.3 For the determination of total recoverable elements in aqueous
samples, samples are not filtered, but acidified with (1+1) nitric
acid to pH < 2 (normally, 3 ml of (1+1) acid per liter of sample is
sufficient for most ambient and drinking water samples). Preservation
may be done at the time of collection, however, to avoid the hazards
of strong acids in the field, transport restrictions, and possible
contamination it is recommended that the samples be returned to the
laboratory within two weeks of collection and acid preserved upon
receipt in the laboratory. Following acidification, the sample should
be mixed, held for sixteen hours, and then verified to be pH < 2 just
prior withdrawing an aliquot for processing or "direct analysis" If
for some reason such as high alkalinity the sample pH is verified to
be > 2, more acid must be added and the sample held for sixteen hours
until verified to be pH < 2. See Section 8.1.
NOTE: When the nature of the sample is either unknown or is known to
be hazardous, acidification should be done in a fume hood
See Section 5.2.
8.4 Solid samples usually require no preservation prior to analysis other
than storage at 4°C. There is no established holding time limitation
for solid samples.
8.5 For aqueous samples, a field blank should be prepared and analyzed as
required by the data user. Use the same container and acid as used in
sample collection.
9.0 QUALITY CONTROL
9.1 Each laboratory using this method is required to operate a formal
quality control (QC) program. The minimum requirements of this program
consist of an initial demonstration of laboratory capability, and the
periodic analysis of laboratory reagent blanks, fortified blanks and
other laboratory solutions as a continuing check on performance. The
laboratory is required to maintain performance records that define the
quality of the data thus generated.
9.2 Initial Demonstration of Performance (mandatory)
9.2.1 The initial demonstration of performance is used to
characterize instrument performance (determination of linear
dynamic ranges and analysis of quality control samples) and
laboratory performance (determination of method detection
limits) prior to samples being analyzed by this method.
9.2.2 Linear dynamic range (LOR) - The upper limit of the LDR must
be established for the wavelength utilized for each analyte by
determining the signal responses from a minimum of six
different concentration standards across the range, two of
200.9-17 Revision 2.2 May 1994
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which are close to the upper limit of the LDR. Determined
LDRs must be documented and kept on file. The linear
calibration range which may be used for the analysis of
samples should be judged by the analyst from the resulting
data. The upper LDR limit should be an observed signal no
more than 10% below the level extrapolated from the four lower
standards. The LDRs should be verified whenever, in the
judgement of the analyst, a change in analytical performance
caused by either a change in instrument hardware or operating
conditions would dictate they be redetermined.
NOTE: Multiple cleanout furnace cycles may be necessary in
order to fully define or utilize the LDR for certain
elements such as chromium. For this reason the upper
limit of the linear calibration range may not
correspond to the upper LDR limit.
Determined sample analyte concentrations that exceed the upper
limit of the linear calibration range must either be diluted
and reanalyzed with concern for memory effects (Sect. 4.4) or
analyzed by another approved method.
9.2.3 Quality control sample (QCS) - When beginning the use of this
method, on a quarterly basis or as required to meet data-
quality needs, verify the calibration standards and acceptable
instrument performance with the preparation and analyses of a
QCS (Sect. 7.12). If the determined concentrations are not
within ± 10% of the stated values, performance of the
determinative step of the method is unacceptable. The source
of the problem must be identified and corrected before either
proceeding on with the initial determination of method
detection limits or continuing with on-going analyses.
9.2.4 Method detection limit (MDL) - MDLs must be established for
all analytes, using reagent water (blank) fortified at a
concentration of two to three times the estimated instrument
detection limit.10 To determine MDL values, take seven
replicate aliquots of the fortified reagent water and process
through the entire analytical method. Perform all calculations
defined in the method and report the concentration values in
the appropriate units. Calculate the MDL as follows:
MDL = (t) x (S)
where: t = students' t value for a 99% confidence level and
a standard deviation estimate with n-1 degrees of
freedom [t = 3.14 for seven replicates].
S = standard deviation of the replicate analyses.
Note: If additional confirmation is desired, reanalyze the
seven replicate aliquots on two more nonconsecutive
days and again calculate the MDL values for each day.
200.9-18 Revision 2.2 May 1994
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An average of the three MDL values for each analyte
may provide for a more appropriate MDL estimate. If
the relative standard deviation (RSD) from the analyses
of the seven aliquots is < 10%, the concentration used
to determine the analyte MDL may have been inapprop-
riately high for the determination. If so, this could
result in the calculation of an unrealistically low
MDL. Concurrently, determination of MDL in reagent
water represents a best case situation and does not
reflect possible matrix effects of real world samples.
However, successful analyses of LFMs (Sect. 9.4) and
the analyte addition test described in Section 9.5.1
can give confidence to the MDL value determined in
reagent water. Typical single laboratory MDL values
using this method are given in Table 2.
The MDLs must be sufficient to detect analytes at the required
levels according to compliance monitoring regulation (Sect.
1.2). MDLs should be determined annually, when a new operator
begins work or whenever, in the judgement of the analyst, a
change in analytical performance caused by either a change in
instrument hardware or operating conditions would dictate they
be redetermined.
9.3 Assessing Laboratory Performance (mandatory)
9.3.1 Laboratory reagent blank (LRB) - The laboratory must analyze at
least one LRB (Sect. 7.10.2) with each batch of 20 or fewer
samples of the same matrix. LRB data are used to assess
contamination from the laboratory environment. LRB values
that exceed the MDL indicate laboratory or reagent
contamination should be suspected. When LRB values constitute
10% or more of the analyte level determined for a sample or is
2.2 times the analyte MDL whichever is greater, fresh aliquots
of the samples must be prepared and analyzed again for the
affected analytes after the source of contamination has been
corrected and acceptable LRB values have been obtained.
9.3.2 Laboratory fortified blank (LFB) - The laboratory must analyze
at least one LFB (Sect. 7.10.3) with each batch of samples.
Calculate accuracy as percent recovery using the following
equation:
LFB - LRB
R =
X 100
where: R = percent recovery.
LFB = laboratory fortified blank.
LRB = laboratory reagent blank.
s = concentration equivalent of analyte
added to fortify the LRB solution.
200.9-19
Revision 2.2 May 1994
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If the recovery of any analyte falls outside the required
control limits of 85-115%, that analyte is judged put of
control, and the source of the problem should be identified and
resolved before continuing analyses.
9.3.3 The laboratory must use LFB analyses data to assess laboratory
performance against the required control limits of 85-115%
(Sect.9.3.2). When sufficient internal performance data become
available (usually a minimum of twenty to thirty analyses),
optional control limits can be developed from the mean percent
recovery (x) and the standard deviation (S) of the mean percent
recovery. These data can be used to establish the upper and
lower control limits as follows:
UPPER CONTROL LIMIT = x + 3S
LOWER CONTROL LIMIT = x - 3S
The optional control limits must be equal to or better than the
required control limits of 85-115%. After each five to ten new
recovery measurements, new control limits can be calculated
using only the most recent twenty to thirty data points. Also,
the standard deviation (S) data should be used to established
an on-going precision statement for the level of concentrations
included in the LFB. These data must be kept on file and be
available for review.
9.3.4 Instrument performance check (IPC) solution - For all
determinations the laboratory must analyze the IPC solution
(Sect. 7.11) and a calibration blank immediately following each
calibration, after every tenth sample (or more frequently, if
required) and at the end of the sample run. Analysis of the
calibration blank should always be < the IDL, but > a negative
signal in concentration units equal to the IDL. Analysis of
the IPC solution immediately following calibration must verify
that the instrument is within ± 5% of calibration. Subsequent
analyses of the IPC solution must be within ± 10 % of
calibration. If the calibration cannot be verified within the
specified limits, reanalyze either or both the IPC solution and
the calibration blank. If the second analysis of the IPC
solution or the calibration blank confirm the calibration to be
outside the limits, sample analysis must be discontinued, the
cause determined and/or in the case of drift the instrument
recalibrated. All samples following the last acceptable IPC
solution must be reanalyzed. The analysis data of the
calibration blank and IPC solution must be kept on file with
the sample analyses data.
9.4 Assessing Analyte Recovery and Data Quality
9.4.1 Sample homogeneity and the chemical nature of the sample matrix
can affect analyte recovery and the quality of the data.
Taking separate aliquots from the sample for replicate and
fortified analyses can in some cases assess these effects.
Unless otherwise specified by the data user, laboratory or
200.9-20 Revision 2.2 May 1994
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program, the following laboratory fortified matrix (LFM)
procedure (Sect. 9.4.2) is required. Also, the analyte
addition test (Sect. 9.5.1) can indicate if matrix and other
interference effects are operative in selected samples.
However, all samples must demonstrate a background absorbance
< 1.0 before the test results obtained can be considered
reliable.
9.4.2 The laboratory must add a known amount of each analyte to a
minimum of 10% of the routine samples. In each case the LFM
aliquot must be a duplicate of the aliquot used for sample
analysis and for total recoverable determinations added prior
to sample preparation. For water samples, the added analyte
concentration must be the same as that used in the laboratory
fortified blank (Sect. 9.3.2). For solid samples, however, the
concentration added should be expressed as mg/kg and is
calculated for a 1 g aliquot by multiplying the added analyte
concentration (ng/L) in solution by the conversion factor 0.1
(0.001 x /tg/L x 0.1L/0.001kg = 0.1, Sect. 12.4). Over time,
samples from all routine sample sources should be fortified.
9.4.3 Calculate the percent recovery for each analyte, corrected for
concentrations measured in the unfortified sample, and compare
these values to the designated LFM recovery range of 70-130%.
Recovery calculations are not required if the concentration
added is less than 25% of the unfortified sample concentration.
Percent recovery may be calculated in units appropriate to the
matrix, using the following equation:
C. - C
R = x 100
where: R = percent recovery.
Cs = fortified sample concentration.
C = sample background concentration.
s = concentration equivalent of analyte
added to fortify the sample.
9.4.4 If the recovery of any analyte falls outside the designated LFM
recovery range (but is still within the range of calibration)
and the laboratory performance for that analyte is shown to be
in control (Sect. 9.3), the recovery problem encountered with
the LFM is judged to be either matrix or solution related, not
system related. If the analyte recovery in the LFM is < 70%
and the background absorbance is < 1.0, complete the analyte
addition test (Sect. 9.5.1) on an undiluted portion of the
unfortified sample aliquot. The test results should be
evaluated as follows:
1. If recovery of the analyte addition test (< 85%) confirms
the a low recovery for the LFM, a suppressive matrix
interference is indicated and the unfortified sample aliquot
200.9-21 Revision 2.2 May 1994
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must be analyzed by method of standard additions (Sect.
11.5).
2. If the recovery of the analyte addition test is between 85%
to 115%, a low recovery of the analyte in the LFM (< 70%)
may be related to the heterogeneous nature of the sample,
the result of precipitation loss during sample preparation,
or an incorrect addition prior to preparation. Report
analyte data determined from the analysis of the unfortified
sample aliquot.
9.4.5 If laboratory performance is shown to be in control (Sect.
9.3), but analyte recovery in the LFM is either > 130% or above
the upper calibration limit and the background absorbance is <
1.0, complete the analyte addition test (Sect. 9.5.1) on a
portion of the unfortified sample aliquot. (If the determined
LFM concentration is above the upper calibration limit, dilute
a portion of the unfortified aliquot accordingly with acidified
reagent water before completing the analyte addition test.)
Evaluate the test results as follows:
1. If the percent recovery of the analyte addition test is >
115%, an enhancing matrix interference (albeit rare) is
indicated and the unfortified sample aliquot or its
appropriate dilution must be analyzed by method of standard
additions (Sect 11.5).
2. If the percent recovery of the analyte addition test is
between 85% to 115%, high recovery in the LFM may have been
caused by random sample contamination, an incorrect addition
of the analyte prior to sample preparation, or sample
heterogeneity. Report analyte data determined from the
analysis of the unfortified sample aliquot or its
appropriate dilution.
3. If the percent recovery of the analyte addition test is <
85%, either a case of both random contamination and an
operative matrix interference in the LFM is indicated or a
more plausible answer is a heterogenous sample with an
suppressive matrix interference. Reported data should be
flagged accordingly.
9.4.6 If laboratory performance is shown to be in control (Sect.
9.3), but the magnitude of the sample (LFM or unfortified
aliquot) background absorbance is > 1.0, a non-specific
spectral interference should be suspected. A portion of the
unfortified aliquot should be diluted (1+3) with acidified
reagent water and reanalyzed. (Dilution may dramatically reduce
a molecular background to an acceptable level. Ideally, the
background absorbance in the unfortified aliquot diluted (1+3)
should be < 1.0. However, additional dilution may be
necessary.) If dilution reduces the background absorbance to
acceptable level (< 1.0), complete the analyte addition test
(Sect. 9.5.1) on a portion of the diluted unfortified aliquot.
200.9-22 Revision 2.2 May 1994
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Evaluate the test results as follows:
1. If the recovery of the analyte addition test is between 85%
to 115%, report analyte data determined on the dilution of
the unfortified aliquot.
2. If the recovery of the analyte addition test is outside the
range of 85% to 115%, complete the sample analysis by
analyzing the dilution of the unfortified aliquot by method
of standard additions (Sect. 11.5).
9.4.7 If either the analysis of a LFM sample(s) or application of the
analyte addition test routine indicate an operative
interference, all other samples in the batch which are typical
and have similar matrix to the LFMs or the samples tested must
be analyzed in the same manner. Also, the data user must be
informed when a matrix interference is so severe that it
prevents the successful analysis of the analyte or when the
heterogeneous nature of the sample precludes the use of
duplicate analyses.
9.4.8 Where reference materials are available, they should be
analyzed to provide additional performance data. The analysis
of reference samples is a valuable tool for demonstrating the
ability to perform the method acceptably.
9.5 The following test can be used to assess possible matrix interference
effects and the need to complete the sample analysis by method of
standard additions (MSA). Results of this test should not be
considered conclusive unless the determined sample background
absorbance is < 1.0. Directions for MSA are given in Section 11.5.
9.5.1 Analyte addition test: An analyte standard added to a portion
of a prepared sample, or its dilution, should be recovered to
within 85% to 115% of the known value. The analyte addition
may be added directly to sample in the furnace and should
produce a minimum level absorbance of 0.1. The concentration
of the analyte addition plus that in the sample should not
exceed the linear calibration range of the analyte. If the
analyte is not recovered within the specified limits, a matrix
effect should be suspected and the sample must be analyzed by
MSA (Sect. 11.5).
10.0 CALIBRATION AND STANDARDIZATION
10.1 Specific wavelengths and instrument operating conditions are listed in
Table 2. However, because of differences among makes and models of
spectrophotometers and electrothermal furnace devices, the actual
instrument conditions selected may vary from those listed.
10.2 Prior to the use of this method the instrument operating conditions
must be optimized. The analyst should follow the instructions
provided by the manufacturer while using the conditions listed in
Table 2 as a guide. Of particular importance is the determination of
200.9-23 Revision 2.2 May 1994
-------
the charring temperature limit for each analyte. This limit is the
furnace temperature setting where a loss in analyte will occur prior
to atomization. This limit should be determined by conducting char
temperature profiles for each analyte and when necessary, in the
matrix of question. The charring temperature selected should minimize
background absorbance while providing some furnace temperature
variation without loss of analyte. For routine analytical operation
the charring temperature is usually set at least 100°C below this
limit. The optimum conditions selected should provide the lowest
reliable MDLs and be similar to those listed in Table 2. Once the
optimum operating conditions are determined, they should be recorded
and available for daily reference.
10.3 Prior to an initial calibration the linear dynamic range of the
analyte must be determined (Sect. 9.2.2) using the optimized
instrument operating conditions (Sect. 10.2). For all determinations
allow an instrument and hollow cathode lamp warm up period of not less
than 15 min. If an EDL is to be used, allow 30 min for warm up.
10.4 Before using the procedure (Sect. 11.0) to analyze samples, there must
be data available documenting initial demonstration of performance.
The required data and procedure are described in Section 9.2. This
data must be generated using the same instrument operating conditions
and calibration routine (Sect. 11.4) to be used for sample analysis.
These documented data must be kept on file and be available for review
by the data user.
10.5 In order to meet or achieve lower MDLs than those listed in Table 2
for "direct analysis" of drinking water with turbidity < 1 NTU
preconcentration of the analyte is required. This may be accomplished
prior to sample introduction into the GFAA or with the use of multiple
aliquot depositions on the GFAA platform or associated delayed
atomization device. When using multiple depositions, the same number
of equal volume aliquots alike of either the calibration standards or
acid preserved samples must be deposited prior to atomization.
Following each deposition the drying cycle is completed before the
next subsequent deposition. The matrix modifier is added along with
each deposition and the total volume of each deposition must not
exceed the instrument manufactures recommended capacity of the delayed
atomization device. To reduce analysis time the minimum number of
depositions required to achieve the desired analytical result should
be used. Use of this procedural technique for the "direct analysis"
of drinking water must be completed using determined optimized
instrument operating conditions for multiple depositions (Sect.10.2)
and comply with the method requirements described in Sections 10.3 and
10.4. (See Table 3 for information and data on the determination of
arsenic by this procedure.)
11.0 PROCEDURE
11.1 Aqueous Sample Preparation - Dissolved Analytes
11.1.1 For the determination of dissolved analytes in ground and
surface waters, pipet an aliquot (> 20 ml) of the filtered,
200.9-24 Revision 2.2 May 1994
-------
acid preserved sample into a 50-mL polypropylene centrifuge
tube. Add an appropriate volume of (1+1) nitric acid to adjust
the acid concentration of the aliquot to approximate a 1% (v/v)
nitric acid solution (e.g., add 0.4 ml (1+1) HNO, to a 20 ml
aliquot of sample). Cap the tube and mix. The sample is now
ready for analysis (Sect. 1.3). Allowance for sample dilution
should be made in the calculations.
NOTE: If a precipitate is formed during acidification,
transport, or storage, the sample aliquot must be
treated using the procedure described in Sections
11.2.2 thru 11.2.7 prior to analysis.
11.2 Aqueous Sample Preparation - Total Recoverable Analytes
11.2.1 For the "direct analysis" of total recoverable analytes in
drinking water samples containing turbidity < 1 NTU, treat an
unfiltered acid preserved sample aliquot using the sample
preparation procedure described in Section 11.1.1 while making
allowance for sample dilution in the data calculation (Sects.
1.2 & 1.4). For the determination of total recoverable
analytes in all other aqueous samples follow the procedure
given in Sections 11.2.2 through 11.2.7.
11.2.2 For the determination of total recoverable analytes in aqueous
samples (other than drinking water with < 1 NTU turbidity)
transfer a 100-mL (± 1 ml) aliquot from a well mixed, acid
preserved sample to a 250-mL Griffin beaker (Sects. 1.2, &
1.6). (When necessary, smaller sample aliquot volumes may be
used.)
NOTE: If the sample contains undissolved solids > 1%, a well
mixed, acid preserved aliquot containing no more than
1 g particulate material should be cautiously
evaporated to near 10 ml and extracted using the acid-
mixture procedure described in Sections 11.3.3 thru
11.3.6. b
11.2.3 Add 2 ml (1+1) nitric acid and 1.0 ml of (1+1) hydrochloric
acid to the beaker containing the measured volume of sample.
Place the beaker on the hot plate for solution evaporation.
The hot plate should be located in a fume hood and previously
adjusted to provide evaporation at a temperature of
approximately but no higher than 85°C. (See the following
note.) The beaker should be covered with an elevated watch
glass or other necessary steps should be taken to prevent
sample contamination from the fume hood environment.
NOTE: For proper heating adjust the temperature control of
the hot plate such that an uncovered Griffin beaker
containing 50 ml of water placed in the center of the
hot plate can be maintained at a temperature
approximately but no higher than 85°C. (Once the beaker
200.9-25 Revision 2.2 May 1994
-------
is covered with a watch glass the temperature of the
water will rise to approximately 95°C.)
11.2.4 Reduce the volume of the sample aliquot to about 20 ml by
gentle heating at 85°C. DO NOT BOIL. This step takes about 2
h for a 100 mL aliquot with the rate of evaporation rapidly
increasing as the sample volume approaches 20 ml. (A spare
beaker containing 20 ml of water can be used as a gauge.)
11.2.5 Cover the lip of the beaker with a watch ^glass to reduce
additional evaporation and gently reflux the sample for 30
minutes. (Slight boiling may occur, but vigorous boiling must
be avoided to prevent loss of the HC1-H20 azeotrope.)
11.2.6 Allow the beaker to cool. Quantitatively transfer the sample
solution to a 50-mL volumetric flask, make to volume with
reagent water, stopper and mix.
11.2.7 Allow any undissolved material to settle overnight, or
centrifuge a portion of the prepared sample until clear. (If
after centrifuging or standing overnight the sample contains
suspended solids that would clog or affect the sample
introduction system, a portion of the sample may be filtered
for their removal prior to analysis. However, care should be
exercised to avoid potential contamination from filtration.)
The sample is now ready for analysis. Because the effects of
various matrices on the stability of diluted samples cannot be
characterized, all analyses should be performed as soon as
possible after the completed preparation.
11.3 Solid Sample Preparation - Total Recoverable Analytes
11.3.1 For the determination of total recoverable analytes in solid
samples, mix the sample thoroughly and transfer a portion
(> 20 g) to tared weighing dish, weigh the sample and record
the wet weight (WW). (For samples with < 35% moisture a 20 g
portion is sufficient. For samples with moisture > 35% a
larger aliquot 50-100 g is required.) Dry the sample to a
constant weight at 60°C and record the dry weight (DW) for
calculation of percent solids (Sect. 12.6). (The sample is
dried at 60°C to prevent the possible loss of volatile metallic
compounds, to facilitate sieving, and to ready the sample for
grinding.)
11.3.2 To achieve homogeneity, sieve the dried sample using a 5-mesh
polypropylene sieve and grind in a mortar and pestle. (The
sieve, mortar and pestle should be cleaned between samples.)
From the dried, ground material weigh accurately a
representative 1.0 ± 0.01 g aliquot (W) of the sample and
transfer to a 250-mL Phillips beaker for acid extraction (Sect.
1.6).
11.3.3 To the beaker add 4 ml of (1+1) HN03 and 10 ml of (1+4) HC1.
Cover the lip of the beaker with a watch glass. Place the
200.9-26 Revision 2.2 May 1994
-------
beaker on a hot plate for reflux extraction of the analytes.
The hot plate should be located in a fume hood and previously
adjusted to provide a reflux temperature of approximately
95°C. (See the following note.)
NOTE: For proper heating adjust the temperature control of
the hot plate such that an uncovered Griffin beaker
containing 50 ml of water placed in the center of the
hot plate can be maintained at a temperature
approximately but no higher than 85°C. (Once the beaker
is covered with a watch glass the temperature of the
water will rise to approximately 95°C.) Also, a block
digester capable of maintaining a temperature of 95°C
and equipped with 250-mL constricted volumetric
digestion tubes may be substituted for the hot plate
and conical beakers in the extraction step.
11.3.4 Heat the sample and gently reflux for 30 min. Very slight
boiling may occur, however vigorous boiling must be avoided to
prevent loss of the HC1-H?0 azeotrope. Some solution
evaporation will occur (3 to 4 ml).
11.3.5 Allow the sample to cool and quantitatively transfer the
extract to a 100-mL volumetric flask. Dilute to volume with
reagent water, stopper and mix.
11.3.6 Allow the sample extract solution to stand overnight to
separate insoluble material or centrifuge a portion of the
sample solution until clear. (If after centrifuging or
standing overnight the extract solution contains suspended
solids that would clog or affect the sample introduction
system, a portion of the extract solution may be filtered for
their removal prior to analysis. However, care should be
exercised to avoid potential contamination from filtration.)
The sample extract is now ready for analysis. Because the
effects of various matrices on the stability of diluted samples
cannot be characterized, all analyses should be performed as
soon as possible after the completed preparation.
11.4 Sample Analysis
11.4.1 Prior to daily calibration of the instrument inspect the
graphite furnace, the sample uptake system and autosampler
injector for any change in the system that would affect
instrument performance. Clean the system and replace the
graphite tube and/or platform when needed or on a daily basis.
11.4.2 Before beginning daily calibration the instrument system should
be reconfigured to the selected optimized operating conditions
as determined in Sections 10.1 and 10.2 or 10.5 for the "direct
analysis" drinking water with turbidity < 1 NTU. Initiate data
system and allow a period of not less than 15 min for
instrument and hollow cathode lamp warm up. If an EDL is to be
used, allow 30 min for warm up.
200.9-27 Revision 2.2 May 1994
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11.4.3 After the warm up period but before calibration, instrument
stability must be demonstrated by analyzing a standard solution
with a concentration 20 times the IDL a minimum of five times.
The resulting relative standard deviation (RSD) of absorbance
signals must be < 5%. If the RSD is > 5%, determine and
correct the cause before calibrating the instrument.
11.4.4 For initial and daily operation calibrate the instrument
according to the instrument manufacturer's recommended
procedures using the calibration blank (Sect. 7.10.1) and
calibration standards (Sect. 7.9) prepared at three or more
concentrations within the usable linear dynamic range of the
analyte (Sects. 4.4 & 9.2.2).
11.4.5 An autosampler must be used to introduce all solutions into the
graphite furnace. Once the standard, sample or QC solution
plus the matrix modifier is injected, the furnace controller
completes furnace cycles and cleanout period as programmed.
Analyte signals must be integrated and collected as peak area
measurements. Background absorbances, background corrected
analyte signals, and determined analyte concentrations on all
solutions must be able to be displayed on a CRT for immediate
review by the analyst and be available as hard copy for
documentation to be kept on file. Flush the autosampler
solution uptake system with the rinse blank (Sect. 7.10.4)
between each solution injected.
11.4.6 After completion of the initial requirements of this method
(Sects. 10.4), samples should be analyzed in the same
operational manner used in the calibration routine.
11.4.7 During the analysis of samples, the laboratory must comply with
the required quality control described in Sections 9.3 and 9.4.
Only for the determination of dissolved analytes or the "direct
analysis" of drinking water with turbidity of < 1 NTU is the
sample digestion step of the LRB, LFB, and LFM not required.
11.4.8 For every new or unusual matrix, when practical, it is highly
recommended that an inductively coupled plasma atomic emission
spectrometer be used to screen for high element concentration.
Information gained from this may be used to prevent potential
damage to the instrument and to better estimate which elements
may require analysis by graphite furnace.
11.4.9 Determined sample analyte concentrations that are 90% or more
of the upper limit of calibration must either be diluted with
acidified reagent water and reanalyzed with concern for memory
effects (Sect. 4.4), or determined by another approved test
procedure that is less sensitive. Samples with a background
absorbance > 1.0 must be appropriately diluted with acidified
reagent water and reanalyzed (Sect. 9.4.6). If the method of
standard additions is required, follow the instructions
described in Section 11.5.
200.9-28 Revision 2.2 May 1994
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11.4.10 When it is necessary to assess an operative matrix interference
(e.g., signal reduction due to high dissolved solids), the test
described in Section 9.5 is recommended.
11.4.11 Report data as directed in Section 12.
11.5 Standard Additions - If the method of standard addition is required,
the following procedure is recommended:
11.5.1 The standard addition technique11 involves preparing new
standards in the sample matrix by adding known amounts of
standard to one or more aliquots of the processed sample
solution. This technique compensates for a sample constituent
that enhances or depresses the analyte signal, thus producing
a different slope from that of the calibration standards. It
will not correct for additive interference, which causes a
baseline shift. The simplest version of this technique is the
single-addition method. The procedure is as follows: Two
identical aliquots of the sample solution, each of volume V ,
are taken. To the first (labeled A) is added a small volume vs
of a standard analyte solution of concentration Cs. To the
second (labeled B) is added the same volume Vs of the solvent.
The analytical signals of A and B are measured and corrected for
nonanalyte signals. The unknown sample concentration Cx is
calculated:
where, S. and S5 are the analytical signals (corrected for the
blank) of solutions A and B, respectively. Vs and Cs should be
chosen so that SA is roughly twice SB on the average. It is
best if Vs is made much less than Vx, and thus C is much greater
than Cx, to avoid excess dilution of the sample matrix. If a
separation or concentration step is used, the additions are best
made first and carried through the entire procedure. For the
results from this technique to be valid, the following
limitations must be taken into consideration:
1. The analytical curve must be linear.
2. The chemical form of the analyte added must respond in the
same manner as the analyte in the sample.
3. The interference effect must be constant over the working
range of concern.
4. The signal must be corrected for any additive interference.
200.9-29 Revision 2.2 May 1994
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12.0 DATA ANALYSIS AND CALCULATIONS
12.1 Sample data should be reported in units of /zg/L for aqueous samples
and mg/kg dry weight for solid samples.
12.2 For dissolved aqueous analytes (Sect. 11.1) report the data generated
directly from the instrument with allowance for sample dilution. Do
not report analyte concentrations below the IDL.
12.3 For total recoverable aqueous analytes (Sect. 11.2), multiply solution
analyte concentrations by the dilution factor 0.5, when 100 mL aliquot
is used to produce the 50 mL final solution, round the data to the
tenths place and report the data in /zg/L up to three significant
figures. If a different aliquot volume other than 100 mL is used for
sample preparation, adjust the dilution factor accordingly. Also,
account for any additional dilution of the prepared sample solution
needed to complete the determination of analytes exceeding the upper
limit of the calibration curve. Do not report data below the
determined analyte MDL concentration or below an adjusted detection
limit reflecting smaller sample aliquots used in processing or
additional dilutions required to complete the analysis.
12.4 For total recoverable analytes in solid samples (Sect. 11.3), round
the solution analyte concentrations (/zg/L) to the tenths place. Report
the data up to three significant figures as mg/kg dry-weight basis
unless specified otherwise by the program or data user. Calculate the
concentration using the equation below:
C x V x D
Sample Cone, (mg/kg)
dry-weight basis W
where: C = Concentration in extract (fig x O.OQ1/L)
V = Volume of extract (L, 100 mL = 0.1L)
D = Dilution factor (undiluted = 1)
W = Weight of sample aliquot extracted (g x 0.001 = kg)
Do not report analyte data below the estimated solids MDL or an
adjusted MDL because of additional dilutions required to complete the
analysis.
12.5 To report percent solids in solid samples (Sect. 11.3) calculate as
fol1ows:
DW
% solids (S) = x 100
WW
where: DW = Sample weight (g) dried at 60°C
WW = Sample weight (g) before drying
200.9-30 Revision 2.2 May 1994
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NOTE: If the data user, program or laboratory requires that the
reported percent solids be determined by drying at 105°C, repeat
the procedure given in Section 11.3 using a separate portion (>
20 g) of the sample and dry to constant weight at 103-105°C.
12.6 The QC data obtained during the analyses provide an indication of the
quality of the sample data and should be provided with the sample
results.
13.0 METHOD PERFORMANCE
13.1 Instrument operating conditions used for single laboratory testing of
the method and MDLs are listed in Table 2.
13.2 Data obtained from single laboratory testing of the method are
summarized in Table 1A-C for three solid samples consisting of SRM
1645 River Sediment, EPA Hazardous Soil, and EPA Electroplating
Sludge. Samples were prepared using the procedure described in
Section 11.3. For each matrix, five replicates were analyzed, and an
average of the replicates was used for determining the sample
background concentration. Two other pairs of duplicates were
fortified at different concentration levels. The sample background
concentration, mean spike percent recovery, the standard deviation of
the average percent recovery, and the relative percent difference
between the duplicate-fortified determinations are listed in Table 1A-
C. In addition, Table 1D-F contains single-laboratory test data for
the method in aqueous media including drinking water, pond water, and
well water. Samples were prepared using the procedure described in
Section 11.2. For each aqueous matrix five replicates were analyzed,
and an average of the replicates was used for determining the sample
background concentration. Four samples were fortified at the levels
reported in Table 1D-1F. A percent relative standard deviation is
reported in Table 1D-1F for the fortified samples. An average percent
recovery is also reported in Tables 1D-F.
NOTE: Antimony and aluminum manifest relatively low percent recoveries
(see Table 1A, NBS River Sediment 1645).
14.0 POLLUTION PREVENTION
14.1 Pollution prevention encompasses any technique that reduces or
eliminates the quantity or toxicity of waste at the point of
generation. Numerous opportunities for pollution prevention exist
in laboratory operation. The EPA has established a preferred
hierarchy of environmental management techniques that places
pollution prevention as the management option of first choice.
Whenever feasible, laboratory personnel should use pollution
prevention techniques to address their waste generation. When
wastes cannot be feasibly reduced at the source, the Agency
recommends recycling as the next best option.
14.2 For information about pollution prevention that may be applicable to
laboratories and research institutions, consult Less is Better:
200.9-31 Revision 2.2 May 1994
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Laboratory Chemical Management for Waste Reduction, available from
the American Chemical Society's Department of Government Relations
and Science Policy, 1155 16th Street N.W., Washington D.C. 20036.
(202)872-4477.
15.0 WASTE MANAGEMENT
15.1 The Environmental Protection Agency requires that laboratory waste
management practices be conducted consistent with all applicable
rule and regulations. The Agency urges laboratories to protect the
air, water, and land by minimizing and controlling all releases from
hoods and bench operations, complying with the letter and spirit of
any sewer discharge permits and regulations, and by complying with
all solid and hazardous waste regulations, particularly the
hazardous waste identification rules and land disposal restrictions.
For further information on waste management consult The Waste
Management Manual for Laboratory Personnel, available from the
American Chemical Society at the address listed in the Section 15.2.
16.0 REFERENCES
1. U.S. Environmental Protection Agency. Method 200.9, Determination
of Trace Elements by Stabilized Temperature Graphite Furnace Atomic
Absorption Spectrometry, Revision 1.2, 1991.
2. Creed, J.T., T.D. Martin, L.B. Lobring and J.W. O'Dell, Environ.
Sci. Techno!., 26:102-106, 1992.
3. Waltz, B., G. Schlemmar and J.R. Mudakavi, JAAS. 3, 695,
1988.
4. Carcinogens - Working With Carcinogens, Department of Health,
Education, and Welfare, Public Health Service, Center for Disease
Control, National Institute for Occupational Safety and Health,
Publication No. 77-206, Aug. 1977.
5. OSHA Safety and Health Standards, General Industry, (29 CFR
1910), Occupational Safety and Health Administration, OSHA 2206,
(Revised, January 1976).
6. Safety in Academic Chemistry Laboratories, American Chemical
Society Publication, Committee on Chemical Safety, 3rd Edition,
1979.
7. Proposed OSHA Safety and Health Standards, Laboratories,
Occupational Safety and Health Administration, Federal Register,
July 24, 1986.
8. Rohrbough, W.G. et al. Reagent Chemicals, American Chemical Society
Specifications, 7th edition. American Chemical Society, Washington,
DC, 1986.
200.9-32 Revision 2.2 May 1994
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9. American Society for Testing and Materials. Standard Specification
for Reagent Water, D1193-77. Annual Book of ASTM Standards, Vol.
11.01. Philadelphia, PA, 1991.
10. Code of Federal Regulation 40, Ch. 1, Pt. 136, Appendix B.
11. Winefordner, J.D., Trace Analysis: Spectroscopic Methods for
Elements, Chemical Analysis, Vol. 46, pp. 41-42.
200.9-33 Revision 2.2 May 1994
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TABLE 2. RECOMMENDED GRAPHITE FURNACE OPERATING CONDITIONS
AND RECOMMENDED MATRIX MODIFIER1"3
El ement
Ag
Al
As7
Be
Cd
Co
Cr
Cu
Fe
Mn
Ni
Pb
Sb7
Se7
Sn7
Tl
Wavelength
328.1
309.3
193.7
234.9
228.8
242.5
357.9
324.8
248.3
279.5
232.0
283.3
217.6
196.0
286.3
276.8
Slit
0.7
0.7
0.7
0.7
0.7
0.2
0.7
0.7
0.2
0.2
0.2
0.7
0.7
2.0
0.7
0.7
Temperature
Char
1000
1700
1300
1200
800
1400
1650
1300
1400
1400
1400
1250
1100
1000
14008
1000
(C)5 Atom
1800
2600
2200
2500
1600
2500
26006
26006
2400
2200
2500
2000
2000
2000
2300
1600
MDL4
(ra/L)
0.59
7.89
0.5
0.02
0.05
0.7
0.1
0.7
-
0.3
0.6
0.7
0.8
0.6
1.7
0.7
1 Matrix Modifier - 0.015 mg Pd + 0.01 mg Mg(N03)2.
2 A 5% H? in Ar gas mix is used during the dry and char steps at 300 mL/min
for al1 elements.
3 A cool down step between the char and atomization is recommended.
4 Obtained using a 20-juL sample size and stop flow atomization.
5 Actual char and atomization temperatures may vary from instrument to
instrument and are best determined on an individual basis. The actual
drying temperature may vary depending on the temperature of the water used
to cool the furnace.
6 A 7-s atomization is necessary to quantitatively remove the analyte from
the graphite furnace.
7 An electrodeless discharge lamp was used for this element.
8 An additional low temperature (approximately 200°C) per char is
recommended.
9 Pd modifier was determined to have trace level contamination of this
element.
200.9-40
Revision 2.2 May 1994
-------
TABLE 3. MULTIPLE DEPOSITION - ARSENIC PRECISION AND RECOVERY DATA1'2
Drinking Water
Source
Cinti. Ohio
Home Cistern
Region I
Region VI
Region X
NIST 1643c*
Average
Cone. ng/L
0.3
0.2
0.7
2.6
1.1
3.9
%RSD
. 41%
15%
7.3%
3.4%
4.8%
7.1%
Fortified
Cone. jug/L
3.8
4.1
5.0
6.7
5.0
—
%RSD
3.9%
1.7%
1.9%
4.3%
1.7%
—
Percent
Recovery
88%
98%
108%
103%
97%
95%
The recommended instrument conditions given in Table 2 were used in this
procedure except for using diluted (1+2) matrix modifier and six - 36 uL
depositions (30 0L sample + 1 pi reagent water + 5 /*L matrix modifier) for
each determination (Sect. 10.5). The amount of matrix modifier deposited on
the platform with each determination (6x5 #L) = 0.030 mg Pd + 0 02 mg
Mg(N03)2. The determined arsenic MDL using this procedure is 0.1
Sample data and fortified sample data were calculated from four and five
replicate determinations, respectively. All drinking waters were fortified
with 4.0 /tg/L arsenic. The instrument was calibrated using a blank and four
standard solutions (1.0, 2.5, 5.0, and 7.5 /jg/L).
* The NIST 1643c reference material Trace Elements in Water was diluted (1+19)
for analysis. The calculated diluted arsenic concentration is 4.1 ug/L The
listed precision and recovery data are from 13 replicate determinations
collected over a period of four days.
200.9-41
Revision 2.2 May 1994
-------
-------
METHOD 200.15
DETERMINATION OF METALS AND TRACE ELEMENTS IN WATER BY ULTRASONIC NEBULIZATION
INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY
Revision 1.2
EMMC Version
|-D- Martin, C.A. Brockhoff, and J.T. Creed - Method 200.15, Revision 1.2
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
200.15-1
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METHOD 200.15
DETERMINATION OF METALS AND TRACE ELEMENTS IN WATER BY ULTRASONIC NEBULIZATION
INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY
1.0 SCOPE AND APPLICATION
1.1 Ultrasonic nebulization inductively coupled plasma-atomic emission
spectrometry (UNICP-AES) is used to determine metals and some
nonmetals in solution. This method provides procedures for the
determination of dissolved and total recoverable elements in ground
waters and surface waters, and total recoverable elements in drinking
water supplies. This method is applicable to the following analytes:
Analyte
Chemical Abstract Services
Registry Numbers (CASRN)
Aluminum
Antimony
Arsenic
Barium
Beryl 1 i urn
Boron
Cadmium
Calcium
Cerium8
Chromi urn
Cobalt
Copper
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silica
Silver
Sodium
(continues
(Al)
(Sb)
(As)
(Ba)
(Be)
(B)
(Cd)
(Ca)
(Ce)
(Cr)
(Co)
(Cu)
(Fe)
(Pb)
(Li)
(Mg)
(Mn)
(Hg)
(Mo)
(Ni)
(K)
(Se)
(Si02)
(Ag)
(Na)
on next page)
7429-90-5
7440-36-0
7440-38-2
7440-39-3
7440-41-7
7440-42-8
7440-43-9
7440-70-2
7440-45-1
7440-47-3
7440-48-4
7440-50-8
7439-89-6
7439-92-1
7439^93-2
7439-95-4
7439-96-5
7439-97-6
7439-98-7
7440-02-0
7440-09-7
7782-49-2
7631-86-9
7440-22-4
7440-23-5
8 Cerium has been included as method analyte for correction of
potential interelement spectral interference.
200.15-2
Revision 1.2 May 1994
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Chemical Abstract Services
Analyte Registry Numbers (CASRN)
Strontium
Thallium
Tin
Titanium
Vanadium
Zinc
(Sr)
(Tl)
(Sn)
(Ti)
(V)
(Zn)
7440-24-6
7440-28-0
7440-31-5
7440-32-6
7440-62-2
7440-66-6
1.2 For reference where this method is approved for use in compliance
monitoring programs [e.g., Clean Water Act (NPDES) or Safe Drinking
Water Act (SDWA)] consult both the appropriate sections of the Code of
Federal Regulation (40 CFR Part 136 Table IB for NPDES, and Part 141
§ 141.23 for drinking water), and the latest Federal Register
announcements.
1.3 Dissolved analytes are determined by UNICP-AES after suitable
filtration, acid preservation, and reagent matrix matching to the
calibration standards. To reduce potential interferences, dissolved
solids should be < 0.2% (w/v) (Sect. 4.2).
1.4 For the determination of total recoverable analytes in aqueous
samples that contain particulate or suspended solids a
digestion/extraction is required prior to analysis. If the sample
contains undissolved solids > 1%, the sample should be analyzed using
one of the other spectrochemical methods - 200.7, 200.8 or 200 9
given in this manual.
1.5 Where this method is approved for the determination of certain metal
and metalloid contaminants in drinking water, samples may be analyzed
directly without acid digestion if the sample has been properly
preserved with acid, has turbidity of < 1 NTU at the time of analysis
and is presented to the instrument in the same reagent/acid matrix as
the calibration standards. This total recoverable determination
procedure is referred to as "direct analysis".
1.6 When determining boron and silica in aqueous samples, only plastic
PTFE or quartz labware should be used from time of sample collection
to completion of analysis. When possible, borosilicate glass should
be avoided to prevent contamination of these analytes.
1.7 Silver is only slightly soluble in the presence of chloride unless
there is a sufficient chloride concentration to form the soluble
chloride complex. This method is suitable for the total recoverable
determination of silver in aqueous samples containing concentrations
up to 0.1 mg/L. For the analysis of water samples containing higher
concentrations of silver, succeeding smaller volume, well mixed
200.15-3 Revision 1.2 May 1994
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aliquots should be prepared until the analysis solution contains < 0.1
mg/L silver.
1.8 The total recoverable sample digestion procedure given in this method
will solubilize and hold in solution only minimal concentrations of
barium in the presence of free sulfate. For the analysis of barium in
samples having varying and unknown concentrations of sulfate, analysis
should be completed as soon as possible after sample preparation.
1.9 This method is not suitable for the determination of organo-mercury
compounds.
1.10 Sample matrices can significantly affect the analytical response of
selenium. The resulting effect is signal enhancement when compared to
a single element calibration standard. The effect can range from 20%
to 60% and is influenced by both the nature and concentration of the
other element(s) in solution. The standardization routine utilized in
this method partially compensates for this enhancement in the analysis
of ambient or drinking waters where the total concentration of the
matrix cations (Ca, K, Mg, & Na) range from 10 mg/L to 300 mg/L.
However, for critical determinations of selenium, method of standard
additions or recognized proven methodology such as graphite furnace
atomic absorption should be used.
1.11 Ultrasonic nebulization being more efficient than direct pneumatic
nebulization a greater portion of the sample aerosol and analyte
reaches the plasma. The increased amount of analyte causes higher
signal intensities which decreases the linear concentration range.
Also, interelement spectral interferences become more significant at
lower concentrations when compared to pneumatic nebulization. Sample
analyte concentrations that exceed 90% of the determined upper limit
of the linear dynamic range should be diluted and reanalyzed.
1.12 Detection limits and linear ranges for the elements will vary with the
wavelength selected, the instrument system, operating conditions, and
sample matrices. Listed in Table 4 are typical method detection
limits determined in reagent blank matrix for the recommended
wavelengths with background correction using the instrument operating
conditions given in Table 5. The MDLs listed are for both total
recoverable determinations by "direct analysis" and where sample
digestion is employed.
1.13 Users of the method data should state the data-quality objectives
prior to analysis. Users of the method must document and have on file
the required initial demonstration performance data described in
Section 9.2 prior to using the method for analysis.
2.0 SUMMARY OF METHOD
2.1 An aliquot of a well mixed, homogeneous sample is accurately weighed
or measured for sample processing. For total recoverable analysis of
a sample containing undissolved material, analytes are first
solubilized by gentle refluxing with nitric and hydrochloric acids.
After cooling, the sample is made up to volume, is mixed and
200.15-4 Revision 1.2 May 1994
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centrifuged or allowed to settle overnight prior to analysis. For the
determination of dissolved analytes in a filtered sample aliquot, or
for the "direct analysis" total recoverable determination of analytes
in drinking water where sample turbidity is < 1 NTU, the sample is
made ready for analysis by the appropriate addition of acids and
hydrogen peroxide,, and then diluted to a predetermined volume and
mixed before analysis.
2.2 The analysis described in this method involves multielemental
determinations by ICP-AES using sequential or simultaneous
instruments. The instruments measure characteristic atomic-line
emission spectra by optical spectrometry. Samples are nebulized and
the resulting aerosol is desolvated before being transported to the
plasma torch. Element specific emission spectra are produced by a
radio-frequency inductively coupled plasma. The spectra are dispersed
by a grating spectrometer, and the intensities of the line spectra are
monitored at specific wavelengths by a photosensitive device.
Photocurrents from the photosensitive device are processed and
controlled by a computer system. A background correction technique is
required to compensate for variable background contribution to the
determination of the analytes. Background must be measured adjacent
to the analyte wavelength during analysis. Various interferences must
be considered and addressed appropriately as discussed in Sections 4
7, 9, 10, and ,11.
3.0 DEFINITIONS
3.1 Calibration Blank - A volume of reagent water acidified with the same
acid matrix as in the calibration standards. The calibration blank is
a zero standard and is used to calibrate the ICP instrument (Sect.
3.2 Calibration Standard (CAL) - A solution prepared from the dilution of
stock standard solutions. The CAL solutions are used to calibrate the
instrument response with respect to analyte concentration (Sect.
/ * 1U ) *
3.3 Dissolved Analyte - The concentration of analyte in an aqueous sample
that will pass through a 0.45-jum membrane filter assembly prior to
sample acidification (Sect. 11.1).
3.4 Field Reagent Blank (FRB) - An aliquot of reagent water or other blank
matrix that is placed in a sample container in the laboratory and
treated as a sample in all respects, including shipment to the
sampling site, exposure to the sampling site conditions, storage,
preservation, and all analytical procedures. The purpose of the FRB
is to determine if method analytes or other interferences are present
in the field environment (Sect 8.4).
3.5 Instrument Detection Limit (IDL) - The concentration equivalent to the
analyte signal which is equal to three times the standard deviation of
a series of ten replicate measurements of the calibration blank signal
at the same wavelength (Table 1).
200.15-5 Revision 1.2 May 1994
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3.6 Instrument Performance Check (IPC) Solution - A solution of method
analytes, used to evaluate the performance of the instrument system
with respect to a defined set of method criteria (Sects. 7.12 &
9.3.4).
3.7 Internal Standard - Pure analyte(s) added to a sample, extract, or
standard solution in known amount(s) and used to measure the relative
responses of other method analytes that are components of the same
sample or solution. The internal standard must be an analyte that is
not a sample component (Sect. 11.4).
3.6 Laboratory Duplicates (LD1 and LD2) - Two aliquots of the same sample
taken in the laboratory and analyzed separately with identical
procedures. Analyses of LD1 and LD2 indicates precision associated
with laboratory procedures, but not with sample collection,
preservation, or storage procedures.
3.9 Laboratory Fortified Blank (LFB) - An aliquot of LRB to which known
quantities of the method analytes are added in the laboratory. The
LFB is analyzed exactly like a sample, and its purpose is to determine
whether the methodology is in control and whether the laboratory is
capable of making accurate and precise measurements (Sects. 7.11.3 &
9.3.2).
3.10 Laboratory Fortified Sample Matrix (LFM) - An aliquot of an
environmental sample to which known quantities of the method analytes
are added in the laboratory. The LFM is analyzed exactly like a
sample, and its purpose is to determine whether the sample matrix
contributes bias to the analytical results. The background
concentrations of the analytes in the sample matrix must be determined
in a separate aliquot and the measured values in the LFM corrected for
background concentrations (Sect. 9.4).
3.11 Laboratory Reagent Blank (LRB) - An aliquot of reagent water or other
blank matrices that are treated exactly as a sample including exposure
to all glassware, equipment, solvents, reagents, and internal
standards that are used with other samples. The LRB is used to
determine if method analytes or other interferences are present in the
laboratory environment, reagents, or apparatus (Sects. 7.11.2 &
9.3.1).
3.12 Linear Dynamic Range (LDR) - The concentration range over which the
instrument response to an analyte is linear (Sect. 9.2.2).
3.13 Method Detection Limit (MDL) - The minimum concentration of an analyte
that can be identified, measured, and reported with 99% confidence
that the analyte concentration is greater than zero (Sect. 9.2.4 and
Table 4).
3.14 Plasma Solution - A solution that is used to determine the optimum
height above the work coil for viewing the plasma (Sects. 7.16 &
10.2.2).
200.15-6 Revi si on 1.2 May 1994
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3.15 Quality Control Sample (QCS) - A solution of method analytes of known
concentrations which is used to fortify an aliquot of LRB or sample
matrix. The QCS is obtained from a source external to the laboratory
and different from the source of calibration standards. It is used to
check either laboratory or instrument performance (Sects. 7.13 &
9.2.3).
3.16 Spectral Interference Check (SIC) Solution - A solution of selected
method analytes of higher concentrations which is used to evaluate the
procedural routine for correcting known interelement spectral
interferences with respect to a defined set of method criteria (Sects
7.14, 7.15 & 9.3.5). -
3.17 Standard Addition - The addition of a known amount of analyte to the
sample in order to determine the relative response of the detector to
an analyte within the sample matrix. The relative response is then
used to assess either an operative matrix effect or the sample analyte
concentration (Sects. 9.5.1 & 11.4).
3.18 Stock Standard Solution - A concentrated solution containing one or
more method analytes prepared in the laboratory using assayed
reference materials or purchased from a reputable commercial source
(Sect. 7.9).
3.19 Total Recoverable Analyte - The concentration of analyte determined
either by "direct analysis" of an unfiltered acid preserved drinking
water sample with turbidity of < 1 NTU (Sect. 11.2.1), or by analysis
of the solution extract of a solid sample or an unfiltered aqueous
sample following digestion by refluxing with hot dilute mineral
acid(s) as specified in the method (Sects. 11.2).
3.20 Water Sample - For the purpose of this method, a sample taken from one
of the following sources: drinking, ambient surface, or ground water.
4.0 INTERFERENCES
4.1 Spectral interferences are caused by background emission from
continuous or recombination phenomena, stray light from the line
emission of high concentration elements, overlap of a spectral line
from another element, or unresolved overlap of molecular band spectra.
4.1.1 Background emission and stray light can usually be compensated
for by subtracting the background emission determined by
measurement(s) adjacent to the analyte wavelength peak.
Spectral scans of samples or single element solutions in the
analyte regions may indicate not only when alternate
wavelengths are desirable because of severe spectral
interference, but also will show whether the most appropriate
estimate of the background emission is provided by an
interpolation from measurements on both sides of the
wavelength peak or by the measured emission on one side or the
other. The location(s) selected for the measurement of
background intensity will be determined by the complexity of
the spectrum adjacent to the wavelength peak. The location(s)
200.15-7 Revision 1.2 May 1994
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used for routine measurement must be free of off-line spectral
interference (interelement or molecular) or adequately
corrected to reflect the same change in background intensity
as occurs at the wavelength peak.
4.1.2 Spectral overlaps may be avoided by using an alternate
wavelength or can be compensated for by equations that correct
for interelement contributions, which involves measuring the
interfering elements. Some potential on-line spectral
interferences observed for the recommended wavelengths are
given in Table 2. When operative and uncorrected, these
interferences will produce false-positive determinations and
be reported as analyte concentrations. The interferences
listed are only those that occur between method analytes.
Only interferences of a direct overlap nature that were
observed with a single instrument having a working resolution
of 0.035 nm are listed. More extensive information on
interferant effects at various wavelengths and resolutions is
available in Boumans' Tables.3 Users may apply interelement
correction factors determined on their instruments within
tested concentration ranges to compensate (off-line or on-
line) for the effects of interfering elements.
4.1.3 When interelement corrections are applied, there is a need to
verify their accuracy by analyzing spectral interference check
solutions as described in Section 7.14. Interelement
corrections will vary for the same emission line among
instruments because of differences in resolution, as
determined by the grating plus the entrance and exit slit
widths, and by the order of dispersion. Interelement
corrections will also vary depending upon the choice of
background correction points. Selecting a background
correction point where an interfering emission line may appear
should be avoided when practical. Interelement corrections
that constitute a major portion of an emission signal may not
yield accurate data. Users should not forget that some
samples may contain uncommon elements that could contribute
spectral interferences.3'4
4.1.4 The interference effects must be evaluated for each individual
instrument whether configured as a sequential or simultaneous
instrument. For each instrument, intensities will vary not
only with optical resolution but also with operating
conditions (such as power, viewing height and argon flow
rate). When using the recommended wavelengths given in Table
1, the analyst is required to determine and document for each
wavelength the effect from the known interferences given in
Table 2, and to utilize a computer routine for their automatic
correction on all analyses. To determine the appropriate
location for off-line background correction, the user must
scan the area on either side adjacent to the wavelength and
record the apparent emission intensity from all other method
analytes. This spectral information must be documented and
kept on file. The location selected for background correction
200.15-8 Revision 1.2 May 1994
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must be either free of off-line interelement spectral
interference or a computer routine must be used for their
automatic correction on all determinations. If a wavelength
other than the recommended wavelength is used, the user must
determine and document both the on-line and off-line spectral
interference effect from all method analytes and provide for
their automatic correction on all analyses. Tests to
determine the spectral interference must be done using
analyte concentrations that will adequately describe the
interference, but not exceed the upper LDR limit of the
analyte. Normally, for ultrasonic nebulization 20 mg/L single
element solutions are sufficient, however, for the major
constituent analytes (calcium, magnesium, potassium and
sodium) found in all waters, or other analytes encountered at
elevated levels, a more appropriate test would be to use a
concentration near the upper LDR limit (Sect. 9.2.2). See
Section 10.4 for required spectral interference test criteria.
4.1.5 When interelement corrections are not used, either on-going
SIC solutions (Sect. 7.15) must be analyzed to verify the
absence of interelement spectral interference or a computer
software routine must be employed for comparing the
determinative data to limits files for notifying the analyst
when an interfering element is detected in the sample at a
concentration that will produce either an apparent false
positive concentration, > the analyte IDL, or false negative
analyte concentration, < the 99% lower control limit of the
calibration blank. When the interference accounts for 10% or
more of the analyte concentration, either an alternate
wavelength free of . interference or another approved test
procedure must be used to complete the analysis. For example,
the copper peak at 213.853 nm could be mistaken for the zinc
peak at 213.856 nm in solutions with high copper and low zinc
concentrations. For this example, a spectral scan in the
213.8-nm region would not reveal the misidentification because
a single peak near the zinc location would be observed. The
possibility of this misidentification of copper for the zinc
peak at 213.856 nm can be identified by measuring the copper
at another emission line, e.g. 324.754 nm. Users should be
aware that, depending upon the instrumental resolution,
alternate wavelengths with adequate sensitivity and freedom
from interference may not be available for all matrices. In
these circumstances the analyte must be determined using
another approved test procedure.
4.2 Physical interferences are effects associated with the sample
nebulization and aerosol transport processes. These effects can cause
significant inaccuracies and can occur especially in samples
containing high dissolved solids or high acid concentrations. Because
ultrasonic nebulization provides more efficient nebulization, these
effects may become more predominant at lower concentrations compared
to pneumatic nebulization. If physical interferences are present
they must be reduced by diluting the sample or using an appropriate
internal standard element. Also, it has been reported that better
200.15-9 Revision 1.2 May 1994
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control of the argon flow rates, especially for the nebulizer,
improves instrument stability and precision; this is accomplished with
the use of mass flow controllers.
4.3 Chemical interferences include molecular-compound formation,
ionization effects, and solute-vaporization effects. Normally, these
effects are not significant with the ICP-AES technique using pneumatic
nebulization, but when evident, are usually matrix dependent.
However, with ultrasonic nebulization the aerosol droplets are
desolvated and the water vapor is removed as condensate before the
analyte enters the plasma. This desolvation step changes the nature
of the aerosol and affects the emission intensity of certain analytes.
A difference in signal intensity has been observed between the stable
valence states of arsenic (As(III) and As(V)) and chromium (Cr(III)
and Cr(VI)) when analyzed as a desolvated aerosol. For arsenic the
higher valance state gives the more intense signal, while for chromium
the opposite is true. A similar phenomenon occurs for selenium,
however, in this situation signal intensity is affected by varying
concentrations of other method analytes in solution. Fortunately, for
arsenic and chromium the effect can be controlled by the addition of
hydrogen peroxide to the mixed acid solutions of samples and
calibration standards alike prior to ultrasonic nebulization. For
selenium the effect is somewhat controlled by approximating the matrix
of the calibration standard to the sample matrix. Effects observed
from the plasma alone can be minimized by careful selection of
operating conditions such as incident power, observation height, and
nebulizer gas flow.
4.4 Memory interferences result when analytes in a previous sample
contribute to the signals measured in a new sample. Memory effects
can result from sample deposition on the uptake tubing to the
nebulizer, and from the buildup of sample material in the plasma torch
and spray chamber. These effects can be minimized by flushing the
system with a rinse blank between samples (Sect. 7.11.4). The
possibility of memory interferences should be recognized within an
analytical run and suitable rinse times should be used to reduce them.
The rinse times necessary for a particular element must be estimated
prior to analysis. This may be achieved by nebulizing a standard
containing elements corresponding to either their LDR or a
concentration ten times those usually encountered. The nebulization
time should be the same as a normal sample analysis period, followed
by analysis of the rinse blank at designated intervals. The length of
time required to reduce analyte signals to within a factor of two of
the method detection limit, should be noted. Until the required rinse
time is established, this method requires a rinse period of at least
60 sec between samples and standards. If a memory interference is
suspected, the sample must be re-analyzed after a long rinse period.
5.0 SAFETY
5.1 The toxicity or carcinogenicity of each reagent used in this method
have not been fully established. Each chemical should be regarded as
a potential health hazard and exposure to these compounds should be as
low as reasonably achievable. Each laboratory is responsible for
200,15-10 Revision 1.2 May 1994
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maintaining a current awareness file of OSHA regulations regarding the
safe handling of the chemicals specified in this method.6"9^ A
reference file of material data handling sheets should also be made
available to all personnel involved in the chemical analysis.
Specifically, concentrated nitric and hydrochloric acids present
various hazards and are moderately toxic and extremely irritating to
skin and mucus membranes. Use these reagents in a fume hood whenever
possible and if eye or skin contact occurs, flush with large volumes
of water. Always wear safety glasses or a shield for eye protection,
protective clothing and observe proper mixing when working with these
reagents.
5.2 The acidification of samples containing reactive materials may result
in the release of toxic gases, such as cyanides or sulfides.
Acidification of samples should be done in a fume hood.
5.3 All personnel handling environmental samples known to contain or to
have been in contact with human waste should be immunized against
known disease causative agents.
5.4 The inductively coupled plasma should only be viewed with proper eye
protection from the ultraviolet emissions.
5.5 It is the responsibility of the user of this method to comply with
relevant disposal and waste regulations. For guidance see Sections
14.0 and 15.0.
6.0 EQUIPMENT AND SUPPLIES
g
6.1 Inductively coupled plasma emission spectrometer:
6.1.1 Computer-controlled emission spectrometer with background-
correction capability. The spectrometer must be capable of
meeting and complying with the requirements described and
referenced in Section 2.2.
6.1.2 Radio-frequency generator compliant with FCC regulations.
6.1.3 Argon gas supply - High purity grade (99.99%). When analyses
are conducted frequently, liquid argon is more economical and
requires less frequent replacement of tanks than compressed
argon in conventional cylinders.
6.1.4 A variable speed peristaltic pump is required to deliver both
standard and sample solutions to the nebulizer.
6.1.5 Ultrasonic nebulizer - A radio-frequency powered oscillating
transducer plate capable of providing a densely populated,
extremely fine desolvated aerosol.
6.1.6 (optional) Mass flow controllers to regulate the argon flow
rates, especially the aerosol transport gas, are highly
recommended. Their use will provide more exacting control of
reproducible plasma conditions.
200.15-11 Revision 1.2 May 1994
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6.2 Analytical balance, with capability to measure to 0.1 mg, for use in
preparing standards, and for determining dissolved solids.
6.3 A temperature adjustable hot plate capable of maintaining a
temperature of 95°C.
6.4 (optional) A steel cabinet centrifuge with guard bowl, electric timer
and brake.
6.5 A gravity convection drying oven with thermostatic control capable of
maintaining 180°C ± 5°C.
6.6 (optional) An air displacement pipetter capable of delivering volumes
ranging from 0.1 to 2500 /*L with an assortment of high quality
disposable pipet tips.
6.7 Labware - All reusable labware (glass, quartz, polyethylene, PTFE,
FEP, etc.) should be sufficiently clean for the task objectives.
Several procedures found to provide clean labware include washing with
a detergent solution, rinsing with tap water, soaking for 4 h or more
in 20% (v/v) nitric acid or a mixture of HN03 and HC1 (1+2+9), rinsing
with reagent water and storing clean.1'2 Chromic acid cleaning
solutions must be avoided because chromium is an analyte.
6.7.1 Glassware - Volumetric flasks, graduated cylinders, funnels
and centrifuge tubes (glass and/or metal-free plastic).
6.7.2 Assorted calibrated pipettes.
*
6.7.3 Griffin beakers, 250-mL with 75-mm watch glasses and
(optional) 75-mm ribbed watch glasses.
6.7.4 (optional) PTFE and/or quartz Griffin beakers, 250-mL with
PTFE covers.
6.7.5 Narrow-mouth storage bottles, FEP (fluorinated ethylene
propylene) with screw closure, 125-mL to 1-L capacities.
6.7.6 One-piece stem FEP wash bottle with screw closure, 125-mL
capacity.
7.0 REAGENTS AND STANDARDS
7.1 Reagents may contain elemental impurities which might affect
analytical data. Only high-purity reagents that conform to the
American Chemical Society specifications should be used whenever
possible. If the purity of a reagent is in question, analyze for
contamination. All acids used for this method must be of ultra high-
purity grade or equivalent. Suitable acids are available from a
number of manufacturers. Redistilled acids prepared by sub-boiling
distillation are acceptable.
7.2 Hydrochloric acid, concentrated (sp.gr. 1.19) - HC1.
200.15-12 Revision 1.2 May 1994
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7.2.1 Hydrochloric acid (1+1) - Add 500 ml concentrated HC1 to 400
ml reagent water and dilute to 1 L.
7.2.2 Hydrochloric acid (1+20) - Add 10 ml concentrated HC1 to 200
ml reagent water.
7.3 Nitric acid, concentrated (sp.gr. 1.41) - HN03.
7.3.1 Nitric acid (1+1) - Add 500 tnL concentrated HNO, to 400 ml
reagent water and dilute to 1 L.
7.3.2 Nitric acid (1+2) - Add 100 ml concentrated HNO, to 200 ml
reagent water.
7.3.3 Nitric acid (1+5) - Add 50 ml concentrated HNO, to 250 ml
reagent water.
7.3.4 Nitric acid (1+9) - Add 10 ml concentrated HNO, to 90 ml
reagent water.
7.4 Reagent water. All references to water in this method refer to ASTM
Type I grade water.
7.5 Ammonium hydroxide, concentrated (sp. gr. 0.902).
7.6 Tartaric acid, ACS reagent grade.
7.7 Hydrogen peroxide, 30%, not-stabilized certified reagent grade.
7.8 Hydrogen peroxide, 50%, stabilized certified reagent grade.
7.9 Standard Stock Solutions - Stock standards may be purchased or
prepared from ultra-high purity grade chemicals (99.99 to 99.999%
pure). All compounds must be dried for 1 h at 105°C, unless
otherwise specified. It is recommended that stock solutions be stored
in FEP bottles. Replace stock standards when succeeding dilutions for
preparation of calibration standards cannot be verified.
CAUTION: Many of these chemicals are extremely toxic if inhaled or
swallowed (Sect. 5.1). Wash hands thoroughly after handling.
Typical stock solution preparation procedures follow for 1-L
quantities, but for the purpose of pollution prevention, the analyst
is encouraged to prepare smaller quantities when possible.
Concentrations are calculated based upon the weight of the pure
element or upon the weight of the compound multiplied by the fraction
of the analyte in the compound.
From pure element,
weight (mg)
Concentration
volume (L)
200.15-13 Revision 1.2 May 1994
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From pure compound,
weight (mg) x gravimetric factor
Concentration
volume (L)
where:
gravimetric factor = the weight fraction of the analyte
in the compound.
7.9.1 Aluminum solution, stock, 1 ml = 1000 #g Al: Dissolve 1.000 g
of aluminum metal, weighed accurately to at least four
significant figures, in an acid mixture of 4.0 ml of (1+1) HC1
and 1.0 ml of concentrated HN03 in a beaker. Warm beaker
slowly to effect solution. When dissolution is complete,
transfer solution quantitatively to a 1-L flask, add an
additional 10.0 ml of (1+1) HC1 and dilute to volume with
reagent water.
7.9.2 Antimony solution, stock, 1 ml = 1000 /jg Sb: Dissolve 1.000
g of antimony powder, weighed accurately to at least four
significant figures, in 20.0 ml (1+1) HN03 and 10.0 ml
concentrated HC1. Add 100 ml reagent water and 1.50 g
tartaric acid. Warm solution slightly to effect complete
dissolution. Cool solution and add reagent water to volume in
a 1-L volumetric flask.
7.9.3 Arsenic solution, stock, 1 ml = 1000 #g As: Dissolve 1.320 g
of As203 (As fraction = 0.7574), weighed accurately to at
least four significant figures, in 100 ml of reagent water
containing 10.0 ml concentrated NH4OH. Warm solution gently
to effect dissolution. Acidify the solution with 20.0 ml
concentrated HN03 and dilute to volume in a 1-L volumetric
flask with reagent water.
7.9.4 Barium solution, stock, 1 mL = 1000 #g Ba: Dissolve 1.437 g
BaC03 (Ba fraction = 0.6960), weighed accurately to at least
four significant figures, in 150 mL (1+2) HN03 with heating
and stirring to degas and dissolve compound. Let solution
cool and dilute with reagent water in 1-L volumetric flask.
7.9.5 Beryllium solution, stock, 1 mL = 1000 jug Be: DO NOT DRY.
Dissolve 19.66 g BeS04-4H20 (Be fraction = 0.0509), weighed
accurately to at least four significant figures, in reagent
water, add 10.0 mL concentrated HN03, and dilute to volume in
a 1-L volumetric flask with reagent water.
7.9.6 Boron solution, stock, 1 mL = 1000 #g B: DO NOT DRY. Dissolve
5.716 g anhydrous H3B03 (B fraction = 0.1749), weighed
accurately to at least four significant figures, in reagent
water and dilute in a 1-L volumetric flask with reagent water.
Transfer immediately after mixing to a clean FEP bottle to
200.15-14 Revision 1.2 May 1994
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minimize any leaching of boron from the .glass volumetric
container. Use of a nonglass volumetric flask is recommended
to avoid boron contamination from glassware.
7.9.7 Cadmium solution, stock, 1 ml = 1000 /zg Cd: Dissolve 1.000 g
Cd metal, acid cleaned with (1+9) HN03, weighed accurately to
at least four significant figures, in 50 ml (1+1) HNO, with
heating to effect dissolution. Let solution cool and dilute
with reagent water in a 1-L volumetric flask.
7.9.8 Calcium solution, stock, 1 ml = 1000 /ig Ca: Suspend 2.498 g
CaCO, (Ca fraction = 0.4005), dried at 180°C for 1 h before
weighing, weighed accurately to at least four significant
figures, in reagent water and dissolve cautiously with a
minimum amount of (1+1) HN03. Add 10.0 ml concentrated HN03
and dilute to volume in a 1-L volumetric flask with reagent
water.
7.9.9 Cerium solution, stock, 1 mL = 1000 /jg Ce: Slurry 1.228 g Ce02
(Ce fraction = 0.8141), weighed accurately to at least four
significant figures, in 100 mL concentrated HNO, and evaporate
to dryness. Slurry the residue in 20 mL H20, add 50 mL
concentrated HN03, with heat and stirring add 60 mL 50% H202
dropwise in 1 mL increments allowing periods of stirring
between the 1 mL additions. Boil off excess H202 before
diluting to volume in a 1-L volumetric flask with reagent
water.
7.9.10 Chromium solution, stock, 1 mL = 1000 /zg Cr: Dissolve 1.923
g Cr03 (Cr fraction = 0.5200), weighed accurately to at least
four significant figures, in 120 mL (1+5) HN03. When solution
is complete, dilute to volume in a 1-L volumetric flask with
reagent water.
7.9.11 Cobalt solution, stock, 1 mL = 1000 /jg Co: Dissolve 1.000 g
Co metal, acid cleaned with (1+9) HNO,, weighed accurately to
at least four significant figures, in 50.0 mL (1+1) HN03.
Let solution cool and dilute to volume in a 1-L volumetric
flask with reagent water.
7.9.12 Copper solution, stock, 1 mL = 1000 ng Cu: Dissolve 1.000 g Cu
metal, acid cleaned with (1+9) HN03, weighed accurately to at
least four significant figures, in 50.0 mL (1+1) HN03 with
heating to effect dissolution. Let solution cool and dilute
in a 1-L volumetric flask with reagent water.
7.9.13 Iron solution, stock, 1 mL = 1000 #g Fe: Dissolve 1.000 g Fe
metal, acid cleaned with (1+1) HC1, weighed accurately to four
significant figures, in 100 mL (1+1) HC1 with heating to
effect dissolution. Let solution cool and dilute with reagent
water in a 1-L volumetric flask.
7.9.14 Lead solution, stock, 1 mL = 1000 /jg Pb: Dissolve 1.599 g
Pb(N03)2 (Pb fraction = 0.6256), weighed accurately to at
200.15-15 Revision 1.2 May 1994
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least four significant figures, in a minimum amount of (1+1)
HN03. Add 20.0 mL (1+1) HN03 and dilute to volume in a 1-L
volumetric flask with reagent water.
7.9.15 Lithium solution, stock, 1 ml = 1000 #g Li: Dissolve 5.324 g
Li2C03 (Li fraction = 0.1878), weighed accurately to at least
four significant figures, in a minimum amount of (1+1) HC1 and
dilute to volume in a 1-L volumetric flask with reagent water.
7.9.16 Magnesium solution, stock, 1 mL = 1000 /wj Mg: Dissolve 1.000
g cleanly polished Mg ribbon, accurately weighed to at least
four significant figures, in slowly added 5.0 mL (1+1) HC1
(CAUTION: reaction is vigorous). Add 20.0 mL (1+1) HN03 and
dilute to volume in a 1-L volumetric flask with reagent water.
7.9.17 Manganese solution, stock, 1 mL = 1000 #g Mn: Dissolve 1.000
g of manganese metal, weighed accurately to at least four
significant figures, in 50 mL (1+1) HN03 and dilute to volume
in a 1-L volumetric flask with reagent water.
7.9.18 Mercury solution, stock, 1 mL = 1000 /ig Hg: DO NOT DRY.
CAUTION: highly toxic element. Dissolve 1.354 g HgCl2 (Hg
fraction = 0.7388) in reagent water. Add 50.0 mL concentrated
HN03 and dilute to volume in 1-L volumetric flask with reagent
water.
7.9.19 Molybdenum solution, stock, 1 mL = 1000 /ig Mo: Dissolve 1.500
g Mo03 (Mo fraction = 0.6666), weighed accurately to at least
four significant figures, in a mixture of 100 mL reagent water
and 10.0 mL concentrated NH4OH, heating to effect dissolution.
Let solution cool and dilute with reagent water in a 1-L
volumetric flask.
7.9.20 Nickel solution, stock, 1 mL = 1000 jag Ni: Dissolve 1.000 g
of nickel metal, weighed accurately to at least four
significant figures, in 20.0 mL hot concentrated HN03, cool,
and dilute to volume in a 1-L volumetric flask with reagent
water.
7.9.21 Potassium solution, stock, 1 mL = 1000 /zg K: Dissolve 1.907 g
KC1 (K fraction = 0.5244) dried at llp°C, weighed accurately
to at least four significant figures, in reagent water, add 20
mL (1+1) HC1 and dilute to volume in a 1-L volumetric flask
with reagent water.
7.9.22 Selenium solution, stock, 1 mL = 1000 ng Se: Dissolve 1.405
g Se02 (Se fraction = 0.7116), weighed accurately to at least
four significant figures, in 200 mL reagent water and dilute
to volume in a 1-L volumetric flask with reagent water.
7.9.23 Silica solution, stock, 1 mL = 1000 /jg Si02: DO NOT DRY.
Dissolve 2.964 g (NH4)2SiF6, weighed accurately to at least
four significant figures, in 200 mL (1+20) HC1 with heating at
200.15-16 Revision 1.2 May 1994
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85°C to effect dissolution. Let solution cool and dilute to
volume in a 1-L volumetric flask with reagent water.
7.9.24 Silver solution, stock, 1 ml = 1000 #g Ag: Dissolve 1.000 g
Ag metal, weighed accurately to at least four significant
figures, in 80 ml (1+1) HN03 with heating to effect
dissolution. Let solution cool and dilute with reagent water
in a 1-L volumetric flask. Store solution in amber bottle or
wrap bottle completely with aluminum foil to protect solution
from light.
7.9.25 Sodium solution, stock, 1 mL = 1000 /zg Na: Dissolve 2.542 g
NaCl (Na fraction = 0.3934), weighed accurately to at least
four significant figures, in reagent water. Add 10.0 mL
concentrated HN03 and dilute to volume in a 1-L volumetric
flask with reagent water.
7.9.26 Strontium solution, stock, 1 mL = 1000 jag Sr: Dissolve 1.685
g SrC03 (Sr fraction = 0.5935), weighed accurately to at least
four significant figures, in 200 mL reagent water with
dropwise addition of 100 mL (1+1) HC1. Dilute to volume in a
1-L volumetric flask with reagent water.
7.9.27 Thallium solution, stock, 1 mL = 1000 /ig Tl: Dissolve 1.303 g
T1N03 (Tl fraction = 0.7672), weighed accurately to at least
four significant figures, in reagent water. Add 10.0 mL
concentrated HN03 and dilute to volume in a 1-L volumetric
flask with reagent water.
7.9.28 Tin solution, stock, 1 mL = 1000 /ig Sn: Dissolve 1.000 g Sn
shot, weighed accurately to at least four significant figures,
in 200 mL (1+1) HC1 with heating to effect dissolution. Let
solution cool and dilute with (1+1) HC1 in a 1-L volumetric
flask.
7.9.29 Titanium solution, stock, 1 mL = 1000 /ig Ti: DO NOT DRY
Dissolve 6.138 g (NH4)2TiO(C20,)2«H20 (Ti fraction « 0.1629),
weighed accurately to at least four significant figures, in
100 mL reagent water. Dilute to volume in a 1-L volumetric
flask with reagent water.
7.9.30 Vanadium solution, stock, 1 mL = 1000 /ig V: Dissolve 1.000 g
V metal, acid cleaned with (1+9) HN03, weighed accurately to
at least four significant figures, in 50 mL (1+1) HN03 with
heating to effect dissolution. Let solution cool and dilute
with reagent water to volume in a 1-L volumetric flask.
7.9.31 Yttrium solution, stock 1 mL = 200 /ig Y: Dissolve 0.254 g Y?0,
(Y fraction = 0.7875), weighed accurately to at least four
significant figures, in 50 mL (1+1) HN03, heating to effect
dissolution. Cool and dilute to volume in a 1-L volumetric
flask with reagent water.
200.15-17 Revision 1.2 May 1994
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7.9.32 Zinc solution, stock, 1 ml = 1000 /ng Zn: Dissolve 1.000 g Zn
metal, acid cleaned with (1+9) HN03, weighed accurately to at
least four significant figures, in 50 ml (1+1) HN03 with
heating to effect dissolution. Let solution cool and dilute
with reagent water to volume in a 1-L volumetric flask.
7.10 Mixed Calibration Standard Solutions - Prepare mixed calibration
standard solutions (see Table 3) by combining appropriate volumes of
the stock solutions in 500-mL volumetric flasks containing 20 ml (1+1)
HN03, 10 ml (1+1) HC1, and 2 ml 30% H202 (not-stabilized) and dilute
to volume with reagent water. Prior to preparing the mixed standards,
each stock solution should be analyzed separately to determine
possible spectral interferences or the presence of impurities. Care
should be taken when preparing the mixed standards to ensure that the
elements are compatible and stable together. To minimize the
opportunity for contamination by the containers, it is recommended to
transfer the mixed-standard solutions to acid-cleaned, never-used FEP
fluorocarbon (FEP) bottles for storage. Fresh mixed standards should
be prepared, as needed, with the realization that concentrations can
change on aging. Calibration standards not prepared from primary
standards must be initially verified using a certified reference
solution. For the recommended wavelengths listed in Table 1 some
typical calibration standard combinations are given in Table 3.
NOTE: If the addition of silver to the recommended acid combination
results in an initial precipitation, add 15 ml of reagent
water and warm the flask until the solution clears. For this
acid combination, the silver concentration should be limited
to 0.1 mg/L.
7.11 Blanks - Four types of blanks are required for the analysis. The
calibration blank is used in establishing the analytical curve, the
laboratory reagent blank is used to assess possible contamination from
the sample preparation procedure, the laboratory fortified blank is
used to assess routine laboratory performance and a rinse blank is
used to flush the instrument uptake system and nebulizer between
standards, check solutions, and samples to reduce memory
interferences.
7.11.1 The calibration blank is prepared by adding HN03, HC1 and H202
to reagent water to the same concentrations as used for the
calibration standard solutions. The calibration blank should
be stored in a FEP bottle.
7.11.2 The laboratory reagent blank (LRB) must contain all the
reagents (HN03, HC1, and H202)in the same volumes as used in
the processing of the samples. The LRB must be carried
through the same entire preparation scheme as the samples
including sample digestion, when applicable.
7.11.3 The laboratory fortified blank (LFB) is prepared by fortifying
an aliquot of the laboratory reagent blank to a concentration
of 0.2 mg/L with all analytes of interest except aluminum,
calcium, iron, magnesium, potassium, selenium, silica, silver,
200.15-18 Revision 1.2 May 1994
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and sodium. The elements of calcium, magnesium, and sodium
should be added to a concentration of 10.0 mg/L each, while
silica (Sect. 1.6) and potassium should be added to a
concentration of 5.0 mg/L, and aluminum, iron, and selenium to
a concentration 0.5 mg/L. If silver is included, it should be
added to a concentration of 0.05 mg/L. (The analyzed value
for Se may indicate a positive bias, Sects. 1.10 & 4.3.) The
LFB must be carried through the same entire preparation scheme
as the samples including sample digestion, when applicable.
7.11.4 The rinse blank is prepared by acidifying reagent water to the
same concentrations of the acids as used for the calibration
standard solutions and stored in a convenient manner.
7.12 Instrument Performance Check (IPC) Solution - Two IPC solutions are
used to periodically verify instrument performance during analysis.
They should be prepared in the same acid/hydrogen peroxide mixture as
the calibration standards by combining method analytes at appropriate
concentrations. The first IPC solution should contain 10 mg/L each of
calcium, magnesium, and sodium and 1.0 mg/L of selenium. All other
analytes should be combined in the second IPC solution each to a
recommended concentration of 0.5 mg/L, except for potassium which
should be 5.0 mg/L and silver, which must be limited to concentration
< 0.1 mg/L. The IPC solution should be prepared from the same
standard stock solutions used to prepare the calibration standards and
stored in FEP bottles. (Following verification and if convenient, the
QCS solutions required in Section 7.13 can be substituted for the IPC
solutions.) Agency programs may specify or request that additional
instrument performance check solutions be prepared at specified
concentrations in order to meet particular program needs.
7.13 Quality Control Sample (QCS) - For initial and periodic verification
of calibration standards and instrument performance, analyses of QCS
solutions are required. The QCS must be obtained from an outside
source different from the standard stock solutions and prepared in the
same acid/hydrogen peroxide mixture as the calibration standards. The
QCS for calcium, magnesium, sodium, and selenium should be prepared as
a separate solution from a single element stock solutions with Ca, Mg,
and Na each at a concentration of 10.0 mg/L and Se at a concentration
of 1.0 mg/L (Sects. 1.10 & 4.3). The other analytes can be combined
in a second QCS solution each at concentrations of 0.5 mg/L, except
for potassium which should be 5.0 mg/L and silver, which must be
limited to a concentration of < 0.1 mg/L for solution stability. The
QCS solutions should be stored in FEP bottles and analyzed as needed
to meet data-quality needs. Fresh solutions should be prepared
quarterly or more frequently as needed.
7.14 Spectral Interference Check (SIC) Solutions - When interelement
corrections are applied, SIC solutions are needed containing
concentrations of the interfering elements at levels that will provide
an adequate test of the correction factors.
7.14.1 SIC solutions containing (a) 30 mg/L Fe; (b) 20 mg/L AL; (c)
10 mg/L Ba; (d) 5 mg/L Be; (e) 5 mg/L Cd; (f) 5 mg/L Ce; (g)
200.15-19 Revision 1.2 May 1994
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5 mg/L Co; (h) 5 mg/L Cr; (i) 5 mg/L Cu; (j) 5 mg/L Mn; (k)
5 mg/L Mo; (1) 5 mg/L Ni; (m) 5 mg/L Sri; (n) 20 mg/L Si02; (o)
5 mg/L Ti; (p) 5 mg/L Tl and (q) 5 mg/L V should be prepared
in the same acid/hydrogen peroxide mixture as the calibration
standards and stored in FEP bottles. These solutions can be
used to periodically verify a partial list of the on-line (and
possible off-line) interelement spectral correction factors
for the recommended wavelengths given in Table 1. Other
solutions could achieve the same objective as well.
(Multielement SIC solutions may be prepared and substituted
for the single element solutions provided an analyte is not
subject to interference from more than one interferant in the
solution and the concentration of the interferant is not above
its upper LDR limit, Sect. 9.2.2.)
NOTE: If wavelengths other than those recommended in Table 1
are used, other solutions different from those above (a
thru q) may be required.
7.14.2 For interferences from iron and aluminum, only those
correction factors (positive or negative) when multiplied by
100 to calculate apparent analyte concentrations that exceed
the determined analyte IDL or fall below the lower 3-sigma
control limit of the calibration blank need be tested on a
daily basis.
7.14.3 For the other interfering elements, only those correction
factors (positive or negative) when multiplied by 10 to
calculate apparent analyte concentrations that exceed the
determined analyte IDL or fall below the lower 3-sigma control
limit of the calibration blank need be tested on a daily
basis.
7.14.4 If the correction routine is operating properly, the
determined apparent analyte(s) concentration from analysis of
each interference solution (a thru q) should fall within a
specific concentration range bracketing the calibration blank.
The concentration range is calculated by multiplying the
concentration of the interfering element by the value of the
correction factor being tested and dividing by 10. If after
subtraction of the calibration blank the apparent analyte
concentration is outside (above or below) this range, a change
in the correction factor of more than 10% should be suspected.
The cause of the change should be determined and corrected and
the correction factor should be updated.
NOTE: The SIC solution should be analyzed more than once to
confirm a change has occurred with adequate rinse time
between solutions and before subsequent analysis of the
calibration blank.
7.14.5 If the correction factors tested on a daily basis are found to
be within the 10% criteria for 5 consecutive days, the
required verification frequency of those factors in compliance
200.15-20 Revision 1.2 May 1994
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may be extended to a weekly basis. Also, if the nature of the
samples analyzed is such (e.g., finished drinking water) that
they do not contain concentrations of the interfering elements
at the 1-mg/L level, daily verification is not required;
however, all interelement spectral correction factors must be
verified annually and updated, if necessary.
7.14.6 If the instrument does not display negative values, fortify
the SIC solution with the elements of interest at 0.1 or 0.2
mg/L and test for analyte recoveries that are below 95%. In
the absence of measurable analyte, over-correction could go
undetected because a negative value could be reported as zero.
7.15 For instruments without interelement correction capability or when
interelement corrections are not used, SIC solutions (containing
similar concentrations of the major components in the samples, e.g.,
> 1 mg/L) can serve to verify the absence of effects at the
wavelengths selected. These data must be kept on file with the sample
analysis data. If the SIC solution confirms an operative interference
that is > 10% of the analyte concentration, the analyte must be
determined using a wavelength and background correction location free
of the interference or by another approved test procedure. Users are
advised that high salt concentrations can cause analyte signal
suppressions and confuse interference tests.
7.16 Plasma Solution - The plasma solution is used for determining the
optimum viewing height of the plasma above the work coil prior to
using the method (Sect. 10.2). The solution is prepared by adding a 1-
mL aliquot from each of the stock standard solutions of arsenic, lead,
selenium, and thallium to a 500-mL volumetric flask containing 20 mL
(1+1) HN03, 10 ml (1+1) HC1, and 2 ml 30% H20p (not-stabilized) and
diluting to volume with reagent water. Store in a FEP bottle.
8.0 SAMPLE COLLECTION. PRESERVATION. AND STORAGE
8.1 Prior to the collection of an aqueous sample, consideration should be
given to the type of data required, (i.e., dissolved or total
recoverable), so that appropriate preservation and pretreatment steps
can be taken. The pH of all aqueous samples must be tested
immediately prior to aliquoting for analysis to ensure the sample has
been properly preserved. If properly acid preserved, the sample can
be held up to 6 months before analysis.
8.2 For the determination of the dissolved elements, the sample must be
filtered through a 0.45-/jm pore diameter membrane filter at the time
of collection or as soon thereafter as practically possible. (Glass
or plastic filtering apparatus are recommended to avoid possible
contamination. Only plastic apparatus should be used when the
determinations of boron and silica are critical.) Use a portion of
the filtered sample to rinse the filter flask, discard this portion
and collect the required volume of filtrate. Acidify the filtrate
with (1+1) nitric acid immediately following filtration to pH < 2.
200.15-21 Revision 1.2 May 1994
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8.3 For the determination of total recoverable elements in aqueous
samples, samples are not filtered, but acidified with (1+1) nitric
acid to pH < 2 (normally, 3 ml of (1+1) acid per liter of sample is
sufficient for most ambient and drinking water samples). Preservation
may be done at the time of collection, however, to avoid the hazards
of strong acids in the field, transport restrictions, and possible
contamination it is recommended that the samples be returned to the
laboratory within two weeks of collection and acid preserved upon
receipt in the laboratory. Following acidification, the sample should
be mixed, held for sixteen hours, and then verified to be pH < 2 just
prior withdrawing an aliquot for processing or "direct analysis". If
for some reason such as high alkalinity the sample pH is verified to
be > 2, more acid must be added and the sample held for sixteen hours
until verified to be pH < 2. See Section 8.1.
NOTE: When the nature of the sample is either unknown or is known to
be hazardous, acidification should be done in a fume hood.
See Section 5.2.
8.4 A field blank should be prepared and analyzed as required by the data
user. Use the same container and acid as used in sample collection.
9.0 QUALITY CONTROL
9.1 Each laboratory using this method is required to operate a formal
quality control (QC) program. The minimum requirements of this program
consist of an initial demonstration of laboratory capability, and the
periodic analysis of laboratory reagent blanks, fortified blanks and
other laboratory solutions as a continuing check on performance. The
laboratory is required to maintain performance records that define
the quality of the data thus generated.
9.2 Initial Demonstration of Performance (mandatory).
9.2.1 The initial demonstration of performance is used to
characterize instrument performance (determination of linear
dynamic ranges and analysis of quality control samples) and
laboratory performance (determination of method detection
limits) prior to analyses conducted by this method.
9.2.2 Linear dynamic range (LDR) - The upper limit of the LOR must
be established for each wavelength utilized. It must be
determined from a linear calibration prepared in the normal
manner using the established analytical operating procedure
for the instrument. The LDR should be determined by analyzing
succeedingly higher standard concentrations of the analyte
until the observed analyte concentration is no more than 10%
below the stated concentration of the standard. Determined
LDRs must be documented and kept on file. The LDR which may
be used for the analysis of samples should be judged by the
analyst from the resulting data. Determined sample analyte
concentrations that are greater than 90% of the determined LDR
limit must be diluted and reanalyzed. The LDRs should be
verified annually or whenever, in the judgement of the
200.15-22 Revision 1.2 May 1994
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analyst, a change in analytical performance caused by either
a change in instrument hardware or operating conditions would
dictate they be redetermined.
9.2.3 Quality control sample (QCS) - When beginning the use of this
method, on a quarterly basis, after the preparation of stock or
calibration standard solutions or as required to meet data-
quality needs, verify the calibration standards and acceptable
instrument performance with the preparation and analyses of QCS
solutions (Sect. 7.13). To verify the calibration standards
the determined mean concentrations from 3 analyses of the QCS
must be within ± 5% of the stated values. If the calibration
standard can not be verified, performance of the determinative
step of the method is unacceptable. The source of the problem
must be identified and corrected before either proceeding on
with the initial determination of method detection limits or
continuing with on-going analyses.
9.2.4 Method detection limit (MDL) - MDLs must be established for
all wavelengths utilized, using reagent water (blank) fortified
at a concentration of two to three times the estimated
instrument detection limit.12 To determine MDL values, take
seven replicate aliquots of the fortified reagent water and
process through the entire analytical method. Perform all
calculations defined in the method and report the concentration
values in the appropriate units. Calculate the MDL as follows:
MDL = (t) x (S)
where: t = students' t value for a 99% confidence level and
a standard deviation estimate with n-1 degrees of
freedom [t = 3.14 for seven replicates].
S = standard deviation of the replicate analyses.
Note: If additional confirmation is desired, reanalyze the
seven replicate aliquots on two more nonconsecutive
days and again calculate the MDL values for each day.
An average of the three MDL values for each analyte
may provide for a more appropriate MDL estimate. If
the relative standard deviation (RSD) from the analyses
of the seven aliquots is < 10%, the concentration used
to determine the analyte MDL may have been inapprop-
riately high for the determination. If so, this could
result in the calculation of an unrealistically low
MDL. Concurrently, determination of MDL in reagent
water represents a best case situation and does not
reflect possible matrix effects of real world samples.
However, successful analyses of LFMs (Sect. 9.4) and
the analyte addition test described in Section 9.5.1
can give confidence to the MDL value determined in
reagent water. Typical single laboratory MDL values
using this method are given in Table 4.
200.15-23 Revi si on 1.2 May 1994
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The MDLs must be sufficient to detect analytes at the required
levels according to compliance monitoring regulation (Sect.
1.2). MDLs should be determined annually, when a new operator
begins work or whenever, in the judgement of the analyst, a
change in analytical performance caused by either a change in
instrument hardware or operating conditions would dictate they
be redetermined.
9.3 Assessing Laboratory Performance (mandatory)
9.3.1 Laboratory reagent blank (LRB) - The laboratory must analyze at
least one LRB (Sect. 7.11.2) with each batch of 20 or fewer
samples of the same matrix. LRB data are used to assess
contamination from the laboratory environment. LRB values that
exceed the MDL indicate laboratory or reagent contamination
should be suspected. When LRB values constitute 10% or more of
the analyte level determined for a sample or is 2.2 times the
analyte MDL whichever is greater, fresh aliquots of the samples
must be prepared and analyzed again for the affected analytes
after the source of contamination has been corrected and
acceptable LRB values have been obtained.
9.3.2 Laboratory fortified blank (LFB) - The laboratory must analyze
at least one LFB (Sect. 7.11.3) with each batch of samples.
Calculate accuracy as percent recovery using the following
equation:
LFB - LRB
X 100
where: R = percent recovery.
LFB = laboratory fortified blank.
LRB = laboratory reagent blank.
s = concentration equivalent of analyte
added to fortify the LRB solution.
If the recovery of any analyte falls outside the required
control limits of 85-115%, that analyte is judged out of
control, and the source of the problem should be identified and
resolved before continuing analyses.
9.3.3 The laboratory must use LFB analyses data to assess laboratory
performance against the required control limits of 85-115%
(Sect.9.3.2). When sufficient internal performance data become
available (usually a minimum of twenty to thirty analyses),
optional control limits can be developed from the mean percent
recovery (x) and the standard deviation (S) of the mean percent
recovery. These data can be used to establish the upper and
lower control limits as follows:
UPPER CONTROL LIMIT = x + 3S
LOWER CONTROL LIMIT = x - 3S
200.15-24
Revision 1.2 May 1994
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The optional control limits must be equal to or better than the
required control limits of 85-115%. After each five to ten new
recovery measurements, new control limits can be calculated
using only the most recent twenty to thirty data points. Also,
the standard deviation (S) data should be used to established
an on-going precision statement for the level of concentrations
included in the LFB. These data must be kept on file and be
available for review.
9.3.4 Instrument performance check (IPC) solution - For all
determinations the laboratory must analyze the IPC solution
(Sect. 7.12) and a calibration blank immediately following
daily calibration, after every tenth sample (or more
frequently, if required) and at the end of the sample run.
Analysis of the calibration blank should always be < the
analyte IDL, but > the lower 3-sigma control limit of the
calibration blank. Analysis of the IPC solution immediately
following calibration must verify that the instrument is within
± 10% of calibration with a relative standard deviation < 3%
from replicate integrations > 4. Subsequent analyses of the
IPC solution also must be within ± 10% of calibration. If the
calibration cannot be verified within the specified limits,
reanalyze either or both the IPC solution and the calibration
blank. If the second analysis of the IPC solution or the
calibration blank confirm calibration to be outside the limits,
sample analysis must be discontinued, the cause determined,
corrected and/or the instrument recalibrated. All samples
following the last acceptable IPC solution must be reanalyzed.
The analysis data of the calibration blank and IPC solution
must be kept on file with the sample analyses data.
9.3.5 Spectral interference check (SIC) solution - For all
determinations the laboratory must periodically verify the
interelement spectral interference correction routine by
analyzing SIC solutions. The preparation and required periodic
analysis of SIC solutions and test criteria for verifying the
interelement interference correction routine are given in
Section 7.14. Special cases where on-going verification is
required are described in Section 7.15.
9.4 Assessing Analyte Recovery and Data Quality
9.4.1 Sample homogeneity and the chemical nature of the sample matrix
can affect analyte recovery and the quality of the data.
Taking separate aliquots from the sample for replicate and
fortified analyses can in some cases assess the effect. Unless
otherwise specified by the data user, laboratory or program,
the following laboratory fortified matrix (LFM) procedure (Sect
9.4.2) is required. Also, other tests such as the analyte
addition test (Sect. 9.5.1) and sample dilution test (Sect.
9.5.2) can indicate if matrix effects are operative.
9.4.2 The laboratory must add a known amount of each analyte to a
minimum of 10% of the routine samples. In each case the LFM
200.15-25 Revision 1.2 May 1994
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aliquot must be a duplicate of the aliquot used for sample
analysis and for total recoverable determinations added prior
to sample preparation. The added analyte concentration must be
the same as that used in the laboratory fortified blank (Sect.
9.3.2). Over time, samples from all routine sample sources
should be fortified.
NOTE: The concentration of calcium, magnesium, sodium and
strontium in environmental waters can vary greatly and
are not necessarily predictable. Fortifying these
analytes in routine samples at the same concentration
used for the LFB may prove to be of little use in
assessing data quality for these analytes. For these
analytes sample dilution and reanalysis using the
criteria given in Section 9.5.2 is recommended. Also,
if specified by the data user, laboratory or program,
samples can be fortified at different concentrations,
but even major constituents should be limited to < 10
mg/L so as not to alter the sample matrix and affect
the analysis.
9.4.3 Calculate the percent recovery for each analyte, corrected for
background concentrations measured in the unfortified sample,
and compare these values to the designated LFM recovery range
of 70-130%. Recovery calculations are not required if the
concentration added is less than 30% of the sample background
concentration. Percent recovery may be calculated using the
following equation:
R =
where: R = percent recovery.
Cs = fortified sample concentration.
C = sample background concentration.
s = concentration equivalent of analyte
added to fortify the sample.
9.4.4 If the recovery of any analyte falls outside the designated LFM
recovery range, and the laboratory performance for that analyte
is shown to be in control (Sect. 9.3), the recovery problem
encountered with the fortified sample is judged to be matrix
related, not system related. The data user should be informed
that the result for that analyte in the unfortified sample is
suspect due to either the heterogeneous nature of the sample or
matrix effects and analysis by method of standard addition or
the use of an internal standard(s) (Sect. 11.4) should be
considered.
9.4.5 Where reference materials are available, they should be
analyzed to provide additional performance data. The analysis
of reference samples is a valuable tool for demonstrating the
ability to perform the method acceptably. Reference materials
200.15-26 Revision 1.2 May 1994
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containing high concentrations of analytes can provide
additional information on the performance of the spectral
interference correction routine.
9.5 Assess the possible need for the method of standard additions (MSA) or
internal standard elements by the following tests. Directions for
using MSA or internal standard(s) are given in Section 11.4.
9.5.1 Analyte addition test: An analyte(s) standard added to a
portion of a prepared sample, or its dilution, should be
recovered to within 85% to 115% of the known value. The
analyte(s) addition should produce a minimum level of 20 times
and a maximum of 100 times the method detection limit. If the
analyte addition is < 20% of the sample analyte concentration,
the following dilution test should be used. If recovery of the
analyte(s) is not within the specified limits, a matrix effect
should be suspected, and the associated data flagged
accordingly. The method of additions or the use of an
appropriate internal standard element may provide more accurate
data.
9.5.2 Dilution test: If the analyte concentration is sufficiently
high (minimally, a factor of 50 above the instrument detection
limit in the original solution but < 90% of the linear limit),
an analysis of a 1+4 dilution should agree (after correction
for the fivefold dilution) within ± 10% of the original
determination. If not, a chemical or physical interference
effect should be suspected and the associated data flagged
accordingly. The method of standard additions or the use of an
internal-standard element may provide more accurate data for
samples failing this test.
10.0 CALIBRATION AND STANDARDIZATION
10.1 Specific wavelengths are listed in Table 1. Other wavelengths may be
substituted if they can provide the needed sensitivity and are
corrected for spectral interference. However, because of the
difference among various makes and models of spectrometers, specific
instrument operating conditions cannot be given. The instrument and
operating conditions utilized for determination must be capable of
providing data of acceptable quality to the program and data user.
The analyst should follow the instructions provided by the instrument
manufacturer unless other conditions provide similar or better
performance for a task. Operating conditions using ultrasonic
nebulization usually vary from 1100 to 1500 watts forward power, 12-to
16-mm viewing height, 12 to 19 liters/min argon coolant flow, 0.5 to
1 L/min argon aerosol flow, 1.5 to 2.5 mL/min sample pumping rate with
a 1-min preflush time and measurement time near 1 s per wavelength
peak (for sequential instruments) and near 10 s per sample (for
simultaneous instruments). The ultrasonic nebulizer is normally
operated at < 50 watts incident power with the desolvation temperature
set at 140°C and a condenser temperature of 5°c.
200.15-27 Revision 1.2 May 1994
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10.2 Prior to using this method optimize the plasma operating conditions.
The following procedure is recommended for vertically configured
plasmas. The purpose of plasma optimization is to provide a maximum
signal-to-background ratio for the least sensitive element in the
analytical array. The use of a mass flow controller to regulate the
nebulizer gas flow rate greatly facilitates the procedure.
10.2.1 Ignite the plasma and select an appropriate incident rf power
with minimum reflected power. Turn on the power to the
ultrasonic nebulizer including the heating tube and chiller and
allow both instruments to become thermally stable before
beginning. This usually requires at least 30 to 60 minutes of
operation. Set the peristaltic pump to deliver an uptake rate
between 1.8 and 2.0 mL/min in a steady even flow. While
nebulizing the 200-#g/mL solution of yttrium (Sect. 7.9.31),
follow the instrument manufacturer's instructions and adjust
the aerosol carrier gas flow rate through the nebulizer so a
definitive blue emission region of the plasma extends
approximately from 5 to 20 mm above the top of the work coil.13
Record the nebulizer gas flow rate or pressure setting for
future reference.
10.2.2 After horizontally aligning the plasma and/or optically
profiling the spectrometer, use the selected instrument
conditions from Sections 10.2.1 and nebulize the plasma
solution (Sect. 7.16), containing 2.0 jag/mL each of As, Pb, Se
and Tl. Collect intensity data at the wavelength peak for each
analyte at 1-mm intervals from 14 to 18 mm above the top of the
work coil. (This region of the plasma is commonly referred to
as the analytical zone.) Repeat the process using the
calibration blank. Determine the net signal to blank intensity
ratio for each analyte for each viewing height setting. Choose
the height for viewing the plasma that provides the largest
intensity ratio for the least sensitive element of the four
analytes. If more than one position provides the same ratio,
select the position that provides the highest net intensity
counts for the least sensitive element or accept a compromise
position of the intensity ratios of all four analytes.
10.2.3 The instrument operating condition finally selected as being
optimum should provide the lowest reliable instrument detection
limits and method detection limits. Refer to Tables 1 and 4
for comparison of IDLs and MDLs, respectively.
10.2.4 If either the instrument operating conditions, such as incident
power and/or nebulizer gas flow rate are changed, or a new
torch injector tube having a different orifice i.d. is
installed, the plasma and plasma viewing height should be
reoptimized.
10.2.5 Before daily calibration and after the instrument warmup
period, the nebulizer gas flow must be reset to the determined
optimized flow. If a mass flow controller is being used, it
should be reset to the recorded optimized flow rate. In order
200.15-28 Revision 1.2 May 1994
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to maintain valid spectral interelement correction routines the
nebulizer gas flow rate should be the same from day-to-day (<2%
change).
10.3 Before using the procedure (Section 11.0) to analyze samples, there
must be data available documenting initial demonstration of
performance. The required data and procedure is described in Section
9.2. This data must be generated using the same instrument operating
conditions and calibration routine (Sect. 11.3) to be used for sample
analysis. These documented data must be kept on file and be available
for review by the data user.
10.4 After completing the initial demonstration of performance, but before
analyzing samples, the laboratory must establish and initially verify
an interelement spectral interference correction routine to be used
during sample analysis. A general description concerning spectral
interference and the analytical requirements for background correction
and for correction of interelement spectral interference in particular
are given in Section 4.1. To determine the appropriate location for
: background correction and to establish the interelement interference
correction routine, repeated spectral scan about the analyte
wavelength and repeated analyses of the single element solutions may
be required. Criteria for determining an interelement spectral
interference is an apparent positive or negative concentration on the
analyte that is outside the 3-sigma control limits of the calibration
blank for the analyte. (The upper-control limit is the analyte IDL.)
Once established, the entire routine must be initially and
periodically verified annually or whenever there is a change in
instrument operating conditions (Sect 10.2.5). Only a portion of the
correction routine must be verified more frequently or on a daily
basis. Test criteria and required solutions are described in Section
7.14. Initial and periodic verification data of the routine should be
kept on file. Special cases where on-going verification are required
is described in Section 7.15.
11.0 PROCEDURE
11.1 Aqueous Sample Preparation - Dissolved Analytes
11.1.1 For the determination of dissolved analytes in ground water and
surface waters pipet or accurately transfer an aliquot (> 20
ml) of the filtered, acid preserved sample into a 50-mL
polypropylene centrifuge tube. Add the appropriate volumes of
(1+1) nitric acid and (1+1) hydrochloric acid and 30% hydrogen
peroxide (not-stabilized) to adjust the reagent concentration
of the aliquot to approximate a 2% (v/v) nitric acid, 1% (v/v)
hydrochloric acid, and 0.4% (v/v) 30% hydrogen peroxide
solution (e.g., add 1.0 ml (1+1) HNO,, 0.5 mL (1+1) HC1, and
0.1 ml 30% Hp02 to a 25 ml aliquot of sample). Cap the tube
and mix. The sample is ready for analysis (Sect. 1.3).
Allowance for sample dilution from the addition of acids and
hydrogen peroxide should be made in data calculations.
200.15-29 Revi si on 1.2 May 1994
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NOTE: If a precipitate is formed during acidification,
transport, or storage, the sample aliquot must be
treated using the procedure in Section 11.2 prior to
analysis.
11.2 Aqueous Sample Preparation - Total Recoverable Analytes
11.2.1 For the "direct analysis" of total recoverable analytes in
drinking water samples containing turbidity < 1 NTU, treat an
unfiltered acid preserved sample aliquot using the sample
preparation procedure described in Section 11.1.1 while making
allowance for sample dilution in the data calculation (Sect.
1.2). For the determination of total recoverable analytes in
all other samples follow the procedure given in Sections 11.2.2
through 11.2.7.
11.2.2 For the determination of total recoverable analytes in aqueous
samples (other than drinking water with < 1 NTU turbidity, and
aqueous samples containing undissolved solids > 1%, Sect. 1.4),
transfer a 100-mL (± 1 ml) aliquot from a well mixed, acid
preserved sample to a 250-mL Griffin beaker (Sects. 1.2, 1.3,
1.6, 1.7, 1.8, & 1.9). (When necessary, smaller sample aliquot
volumes may be used.)
11.2.3 Add 2.0 ml (1+1) nitric acid and 1.0 ml of (1+1) hydrochloric
acid to the beaker containing the measured volume of sample.
Place the beaker on the hot plate for solution evaporation.
The hot plate should be located in a fume hood and previously
adjusted to provide evaporation at a temperature of
approximately but no higher than 85°C, (See the following
note.) The beaker should be covered with an elevated watch
glass or other necessary steps should be taken to prevent
sample contamination from the fume hood environment.
NOTE: For proper heating adjust the temperature control of
the hot plate such that an uncovered Griffin beaker
containing 50 ml of water placed in the center of the
hot plate can be maintained at a temperature
approximately but no higher than 85°C. (Once the beaker
is covered with a watch glass the temperature of the
water will rise to approximately 95°C.)
11.2.4 Reduce the volume of the sample aliquot to about 20 ml by
gentle heating at 85°C. DO NOT BOIL. This step takes about 1
h for a 50 ml aliquot with the rate of evaporation rapidly
increasing as the sample volume approaches 20 ml. (A spare
beaker containing 20 mL of water can be used as a gauge.)
11.2.5 Cover the lip of the beaker with a watch glass to reduce
additional evaporation and gently reflux the sample for 30
minutes. (Slight boiling may occur, but vigorous boiling must
be avoided to prevent loss of the HC1-H20 azeotrope.)
200.15-30 Revision 1.2 May 1994
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11.2.6 Allow the beaker to cool. Quantitatively transfer the sample
solution to a 50-mL volumetric flask, add 0.2 ml of 30%
hydrogen peroxide (Sect.7.7), make to volume with reagent
water, stopper and mix.
11.2.7 Allow any undissolved material to settle overnight, or
centrifuge a portion of the prepared sample until clear. (If
after centrifuging or standing overnight the sample contains
suspended solids that would clog the uptake system to the
nebulizer, a portion of the sample may be filtered for their
removal prior to analysis. However, care should be exercised
to avoid potential contamination from filtration.) The sample
is now ready for analysis. Because the effects of various
matrices on the stability of diluted samples cannot be
characterized, all analyses should be performed as soon as
possible after the completed preparation.
11.3 Sample Analysis
11.3.1 Prior to daily calibration of the instrument inspect the sample
introduction system including the nebulizer, torch, injector
tube and uptake tubing for salt deposits, dirt and debris that
would restrict solution flow and affect instrument performance.
Clean the system when needed or on a daily basis.
11.3.2 Configure the instrument system to the selected power and
operating conditions as determined in Sections 10.1 and 10.2.
11.3.3 The instrument and nebulizer system must be allowed to become
thermally stable before calibration and analyses. This usually
requires at least 60 minutes of operation. After instrument
warmup, complete any required optical profiling or alignment
particular to the instrument.
11.3.4 For initial and daily operation calibrate the instrument
according to the instrument manufacturer's recommended
procedures, using mixed calibration standard solutions (Sect.
7.10) and the calibration blank (Sect. 7.11.1). A peristaltic
pump must be used to introduce all solutions to the nebulizer.
To allow equilibrium to be reached in the plasma, nebulize all
solutions for 30 sec after reaching the plasma before beginning
integration of the background corrected signal to accumulate
data. When possible, use the average value of replicate
integration periods of the signal to be correlated to the
analyte concentration. Flush the system with the rinse blank
(Sect. 7.11.4) for a minimum of 60 seconds (Sect. 4.4) between
each standard. The calibration line should consist of a
minimum of a calibration blank and a high standard. Replicates
of the blank and highest standard provide an optimal
distribution of calibration standards to minimize the
confidence band for a straight-line calibration in a response
region with uniform variance.15
200.15-31 Revision 1.2 May 1994
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11.3.5 After completion of the initial requirements of this method
(Sects. 10.3 and 10.4), samples should be analyzed in the same
operational manner used in the calibration routine with the
rinse blank also being used between all sample solutions, LFBs,
LFMs, and check solutions.
11.3.6 During the analysis of samples, the laboratory must comply with
the required quality control described in Sections 9.3 and 9.4.
11.3.7 Determined sample analyte concentrations that are 90% or more
of the upper limit of the analyte LDR must be diluted with
reagent water that has been acidified in the same manner as
calibration blank and reanalyzed (see Sect.11.3.8). Also, for
the interelement spectral interference correction routines to
remain valid during sample analysis, the interferant
concentration must not exceed its LDR. If the interferant LDR
is exceeded, sample dilution with acidified reagent water and
reanalysis is required. In these circumstances analyte
detection limits are raised and determination by another
approved test procedure (Sect. 1.2) that is either more
sensitive and/or interference free is recommended.
11.3.8 When it is necessary to assess an operative matrix interference
(e.g., signal reduction due to high dissolved solids), the
tests described in Section 9.5 are recommended.
11.3.9 Report data as directed in Section 12.
11.4 If the method of standard additions (MSA) is used, standards are added
at one or more levels to portions of a prepared sample. This
technique compensates for enhancement or depression of an analyte
signal by a matrix. It will not correct for additive interferences
such as contamination, interelement interferences, or baseline shifts.
This technique is valid in the linear range when the interference
effect is constant over the range, the added analyte responds the same
as the endogenous analyte, and the signal is corrected for additive
interferences. The simplest version of this technique is the single-
addition method. This procedure calls for two identical aliquots of
the sample solution to be taken. To the first aliquot, a small volume
of standard is added; while to the second aliquot, a volume of acid
blank is added equal to the standard addition. The sample
concentration is calculated by the following:
S2 x V1 x C
Sample Cone =
(mg/L or mg/kg) (SrS2) x V2
where: C = Concentration of the standard solution (mg/L)
S., = Signal for fortified aliquot
S2 = Signal for unfortified aliquot
V1 = Volume of the standard addition (L)
V2 = Volume of the sample aliquot (L) used for MSA
200.15-32 Revision 1.2 May 1994
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For more than one fortified portion of the prepared sample, linear
regression analysis can be applied using a computer or calculator
program to obtain the concentration of the sample solution. An
alternative to using the method of standard additions is use of the
internal standard technique by adding one or more elements (not in the
samples and verified not to cause an uncorrected interelement spectral
interference) at the same concentration (which is sufficient for
optimum precision) to the prepared samples (blanks and standards) that
are affected the same as the analytes by the sample matrix. Use the
ratio of analyte signal to the internal standard signal for
calibration and quantitation.
12.0 DATA ANALYSIS AND CALCULATIONS
12.1 Sample data should be reported in units of /jg/L for all elements
except Ca, K, Mg, Na, and Si02 which should be reported in mg/L.
12.2 For /jg/L data values less than ten, two significant figures should be
used for reporting element concentrations. For data values greater
than or equal to ten, three significant figures should be used. For
the analytes Ca, K, Mg, Na, and Si02 with MDLs < 0.01 mg/L, round the
data values to the thousandth place and report analyte concentrations
up to three significant figures. When the MDLs for those analytes are
> 0.01 mg/L, round the data values to the hundredth place and report
analyte concentrations up to three significant figures.
12.3 For dissolved analytes (Sect. 11.1) and total recoverable analyses of
drinking water with turbidity < 1NTU (Sect. 11.2.1), report the data
generated directly from the instrument with allowance for sample
dilution. Do not report analyte concentrations below the laboratory
determined "direct analysis" IX MDL concentration.
12.4 For total recoverable aqueous analytes (Sects. 11.2.2 - 11.2.7) report
data as instructed in Section 12.2. If a different aliquot volume
other than 100 mL is used for sample preparation, adjust the data
accordingly using the appropriate dilution factor. Also, account for
any additional dilution of the prepared sample solution needed to
complete the determination of analytes exceeding 90% or more of the
LDR upper limit. Do not report data below the laboratory determined
analyte 2X MDL concentration or below an adjusted detection limit
reflecting smaller sample aliquots used in processing or additional
dilutions required to complete the analysis.
12.5 The QC data obtained during the analyses provide an indication of the
quality of the sample data and should be provided with the sample
results.
13.0 METHOD PERFORMANCE
13.1 Listed in Table 4 are typical single laboratory "direct analysis" IX
MDLs and total recoverable preconcentrated 2X MDLs determined for the
recommended wavelengths using simultaneous ICP-AES and the instrument
conditions listed in Table 5. The MDLs were determined in reagent
blank matrix (best case situation). PTFE beakers were used in the
200.15-33 Revision 1.2 May 1994
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total recoverable determinations to avoid boron and silica
contamination from glassware with the final dilution to 50 ml
completed in polypropylene centrifuged tubes. Theoretically the
preconcentrated 2X MDLs should be lower than the "direct analysis" IX
MDLs, however, for those analytes where the 2X MDLs values are
significantly higher (2X MDL > 2 times the IX MDL) environmental
contamination is suspected.
13.2 Data obtained from single laboratory testing of the method are
summarized in Table 6 for four different drinking water supplies (two
ground waters and two surface waters) and an ambient surface water.
The precision and recovery data were collected by simultaneous ICP-AES
utilizing the recommended wavelengths given in Table 1 and the
instrument conditions listed in Table 5. The unfiltered drinking
waters were prepared using the procedure described in Section 11.1
while the total recoverable procedure (Sects. 11.2.2 -11.2.7) was used
to prepare the ambient surface water. For each matrix, five replicate
aliquots were prepared, analyzed and the average of the five
determinations used to define the sample background concentration of
each analyte. In addition, two further pairs of duplicates were
fortified at different concentration levels. For each method analyte,
the sample background concentration, mean percent recovery, the
standard deviation of the percent recovery and the relative percent
difference between the duplicate fortified samples are listed in Table
6. The variance of the five replicate sample background determinations
is included in the calculated standard deviation of the percent
recovery when the analyte concentration in the sample was greater than
the MDL. Fortified sample data for the matrix analytes Ca, K, Mg, Na,
Sr, and Si02 are not included. However, the precision and mean sample
background concentrations for these six analytes are listed separately
in Table 7.
14.0 POLLUTION PREVENTION
14.1 Pollution prevention encompasses any technique that reduces or
eliminates the quantity or toxicity of waste at the point of
generation. Numerous opportunities for pollution prevention exist in
laboratory operation. The EPA has established a preferred hierarchy
of environmental management techniques that places pollution
prevention as the management option of first choice. Whenever
feasible, laboratory personnel should use pollution prevention
techniques to address their waste generation (e.g., Sect. 7.9). When
wastes cannot be feasibly reduced at the source, the Agency recommends
recycling as the next best option.
14.2 For information about pollution prevention that may be applicable to
laboratories and research institutions, consult Less is Better:
Laboratory Chemical Management for Waste Reduction, available from the
American Chemical Society's Department of Government Relations and
Science Policy, 1155 16th Street N.W., Washington D.C. 20036,
(202)872-4477.
200.15-34 Revision 1.2 May 1994
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15.0 WASTE MANAGEMENT
15.1 The Environmental Protection Agency requires that laboratory waste
management practices be conducted consistent with all applicable rules
and regulations. The Agency urges laboratories to protect the air,
water, and land by minimizing and controlling all releases from hoods
and bench operations, complying with the letter and spirit of any
sewer discharge permits and regulations, and by complying with all
solid and hazardous waste regulations, particularly the hazardous
waste identification rules and land disposal restrictions. For
further information on waste management consult The Waste Management
Manual for Laboratory Personnel, available from the American Chemical
Society at the address listed in the Section 14.2.
16.0 REFERENCES
1. U.S. Environmental Protection Agency. Inductively Coupled Plasma -
Atomic Emission Spectrometric Method for Trace Element Analysis of
- Water and Wastes - Method 200.7, Version 3.3, 1991.
2. U.S. Environmental Protection Agency. Inductively Coupled Plasma -
Atomic Emission Spectrometry Method for the Analysis of Waters and
Solids, EMMC, July 1992.
3. Boumans, P.W.J.M. Line Coincidence Tables for Inductively Coupled
Plasma Atomic Emission Spectrometry, 2nd edition. Pergamon Press,
Oxford, United Kingdom, 1984.
4. Winge, R.K. et al. Inductively Coupled Plasma-Atomic Emission
Spectroscopy: An Atlas of Spectral Information, Physical Science Data
20. Elsevier Science Publishing, New York, New York, 1985.
5. Martin, T.D., C.A. Brockhoff and J.T. Creed. Trace Metal Valence
State Consideration in Utilizing an Ultrasonic Nebulizer for Metal
Determination by ICP-AES. Winter Conference on Plasma
Spectrochemistry, San Diego, CA, January, 10-15, 1994.
6. Carcinogens - Working With Carcinogens, Department of Health,
Education, and Welfare, Public Health Service, Center for Disease
Control, National Institute for Occupational Safety and Health,
Publication No. 77-206, Aug. 1977.
7. OSHA Safety and Health Standards, General Industry, (29 CFR
1910), Occupational Safety and Health Administration, OSHA 2206,
(Revised, January 1976).
8. Safety in Academic Chemistry Laboratories, American Chemical
Society Publication, Committee on Chemical Safety, 3rd Edition,
1979.
9. Proposed OSHA Safety and Health Standards, Laboratories, Occupational
Safety and Health Administration, Federal Register, July 24, 1986.
200.15-35 Revi si on 1.2 May 1994
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10. Rohrbough, W.G. et al. Reagent Chemicals, American Chemical Society
Specifications, 7th edition. American Chemical Society, Washington,
DC, 1986.
11. American Society for Testing and Materials. Standard Specification
for Reagent Water, D1193-77. Annual Book of ASTM Standards, Vol.
11.01. Philadelphia, PA, 1991.
12. Code of Federal Regulations 40, Ch. 1, Pt. 136 Appendix B.
13. Wallace, G.F., Some Factors Affecting the Performance of an ICP Sample
Introduction System. Atomic Spectroscopy, Vol. 4, p. 188-192, 1983.
14. Koirtyohann, S.R. et al. Nomenclature System for the Low-Power Argon
Inductively Coupled Plasma, Anal. Chem. 52:1965, 1980
15. Deming, S.N. and S.L. Morgan. Experimental Design for Quality and
Productivity in Research, Development, and Manufacturing, Part III, pp
119-123. Short course publication by Statistical Designs, 9941
Rowlett, Suite 6, Houston, TX 77075, 1989.
16. Winefordner, J.D., Trace Analysis: Spectroscopic Methods for
Elements, Chemical Analysis, Vol. 46, pp. 41-42.
200.15-36 Revision 1.2 May 1994
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17.0 TABLES. DIAGRAMS. FLOWCHARTS. AND VALIDATION DATA
TABLE 1. WAVELENGTHS, ESTIMATED INSTRUMENT DETECTION
LIMITS, AND RECOMMENDED CALIBRATION
Analyte
Aluminum
Antimony
Arsenic
Barium
Beryl 1 i urn
Boron
Cadmium
Calcium
Cerium
Chromium
Cobalt
Copper
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silica (Si02)
Silver
Sodium
Strontium
Thallium
Tin
Titanium
Vanadium
Zinc
Wavelength3
(nm)
308.215
206.833
193.759
493.409
313.042
249.678
226.502
315.887
413.765
205.552
228.616
324.754
259.940
220.353
670.784
279.079
257.610
194.227
203.844
231.604
766.491
196.090
251.611
328.068
588.995
421.552
190.864
189.980
334.941
292.402
213.856
Detection
Limitb
0»g/L)
1
1
3
0.2
0.05
2
0.2
1
20
0.9
0.4
0.3
0.3
2
0.4
2
0.2
3
1
0.8
40
8
10 (Si02)
0.3
3
0.1
5
4
0.1
0.6
0.4
Calibrate0
to
(mg/L)
2
1
2
0.2
0.2
0.5
0.5
40
0.5
1
0.5
0.5
2
2
1
10
0.5
0.5
2
0.5
10
2
2
0.1
20
0.2
1
1
2
0.5
1
a The wavelengths listed are recommended because of their sensitivity and
overall acceptability. Other wavelengths may be substituted if they can
provide the needed sensitivity and are treated with the same corrective
techniques for spectral interference (see Section 4.1).
The listed EMSL-Cincinnati estimated 3-sigma instrumental detection
limits are provided only as a guide to instrumental limits.
Suggested concentration for instrument calibration.
limits in the linear ranges may be used.
Other calibration
200.15-37
Revision 1.2 May 1994
-------
TABLE 2. ON-LINE METHOD INTERELEMENT SPECTRAL INTERFERENCES
ARISING FROM INTERFERANTS AT THE 20-mg/L LEVEL
Analyte
Ag
Al
As
B
Ba
Be
Ca
Cd
Ce
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
Pb
Sb
Se
SiO?
Sn
Sr
Tl
Ti
V
Zn
Wavelength
(nm)
328.068
308.215
193.759
249.678
493.409
313.042
315.887
226.502
413.765
228.616
205.552
324.754
259.940
194.227
766.491
670.784
279.079
257.610
203.844
588.995
231.604
220.353
206.833
196.099
251.611
189.980
421.552
190.864
334.941
292.402
213.856
Interferant*
Ce,Ti,Mn
V,Mo,Ce,Mn
V,Al,Co,Fe,N1
None
None
V,Ce
Co,Mo,Ce
Ni,Ti,Fe,Ce
None
Ti,Ba,Cd,Ni,Cr,Mo,
Be,Mo,Ni,
Moji
None
V,Mo
None
None
Ce
Ce
Ce
None
Co.Tl
Co,Al,Ce,Cu,Ni,Ti,
Cr,Mo,Sn,Ti,Ce,Fe
Fe
None
Mo,Ti,Fe,Mn,Si
None
Ce
Fe
Ti,Mo,Co,Ce,Al,V,Mn
None
Mo,Ti,Cr,Fe,Ce
Ni,Cu,Fe
* These on-line interferences from method analytes and titanium only were
observed using an instrument with 0.035-nm resolution (see Sect. 4.1.2).
Interferant ranked by magnitude of intensity with the most severe interferant
listed first in the row.
200.15-38 Revi si on 1.2 May 1994
-------
TABLE 3. MIXED STANDARD SOLUTIONS1
Solution
Analytes
I
II
III
IV
V
VI
Ag, As, B, Ba, Cd, Cu, Mn, and Sb
K, Li, Mo, Sr, and Ti
Co, V, and Ce
Al, Cr, Hg, Si02, Sn, and In
Be, Fe, Ni, Pb, and Tl
Se, Ca, Mg,and Na
See Table 1 for recommended calibration concentrations. See Sections
1.10 and 4.3 for discussion on desolvation affects on As, Cr, and Se. See
Section 7.10 and 7.11 for preparation of calibration standard and blank
solutions.
200.15-39
Revision 1.2 May 1994
-------
TABLE 4. METHOD DETECTION LIMITS (MDL)(
Analyte
Ag
Al
As
B
Ba
Be
Cd
Ce
Co
Cr
Cu
Fe
Hg
Li
Mn
Mo
N1
Pb
sb*
Se*
Sn
Sr
Ti
Tl
V
Zn
Ca
K
Mg
Na
Si02
IX MDL
Direct Analysis, /tg/L
0.6
4
3
2
0.2
0.05
0.4
5
0.6
2
2
2
3
0.7
0.09
2
0.7
4
3
5
5
0.08
0.2
6
2
0.5
IX MDL. ma/L
0.005
0.09
0.005
0.04
0.002
2X MDL
Total Recoverable Digestion, #g/L<2>
0.6
20
2
4
0.2
0.02
0.2
5
0.4
0.4
0.7
10
2
0.9
0.08
1
0.8
2
3
3
2
0.2
0.3
2
0.5
0.7
2X MDL, mq/L(2>
0.03
0.05
0.01
0.05
0.03
(1) Method detection limits are sample dependent and may vary as the sample
matrix varies.
(2) MDL concentrations are computed for original matrix with allowance for 2x
sample preconcentration during preparation. Samples were processed in PTFE
and diluted in 50-mL plastic centrifuge tubes.
* Se MDL determined in tap water due to common matrix enhancement (Sect. 1.10)
200.15-40
Revision 1.2 May 1994
-------
TABLE 5. INDUCTIVELY COUPLED PLASMA AND ULTRASONIC NEBULIZER
INSTRUMENT OPERATING CONDITIONS
ICP SPECTROMETER
Incident rf power
Reflected rf power
Viewing height above
work coil
Injector tube orifice i.d.
Argon supply
Argon pressure
Coolant argon flow rate
Auxiliary (plasma)
argon flow rate
ULTRASONIC NEBULIZER
Aerosol carrier argon
flow rate
Sample uptake rate
controlled to
Transducer power
1.4 MHz auto-tuned
Desolvation temperature
Condenser temperature
1400 watts
< 5 watts
15 mm
1 mm
liquid argon
40 psi
19 L/min
300 mL/min
570 mL/min
1.8 mL/min
35 watts
140°C
5°C
200.15-41
Revision 1.2 May 1994
-------
TABLE 6. PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES
REGION 2 - TAP WATER
ANALYTE
Ag
Al
As
B
Ba
Be
Cd
Ce
Co
Cr
Cu
Fe
Hg
Li
Mn
Ho
Ni
Pb
Sb
Se
Sn
Ti
Tl
V
Zn
SAMPLE LOW
CONC SPIKE
/zG/L jiG/L
<0.6
10.4
<3
5.3
5.8
<0.05
<0.4
<5.
<0.6
<2
152.
106.
<3
0.72
5.9
<2
<0.7
12.4
<3
<5
<5
<0.2
<6
<2
5.6
10.0
40.0
30.0
20.0
20.0
4.0
4.0
50.0
20.0
20.0
20.0
20.0
30.0
20.0
10.0
20.0
10.0
15.0
30.0
50.0
40.0
20.0
40.0
20.0
20.0
AVERAGE
RECOVERY
R(%)
114
115
118
94
100
101
110
107
102
101
*
*
106
100
101
96
111
107
112
94
106
102
119
103
108
S(R)
2.0
3.8
0.7
3.8
1.6
0.9
0.4
0.1
1.4
1.0
*
*
2.2
1.9
1.9
3.3
0.4
8.8
0.3
1.9
1.2
1.3
1.6
2.0
1.2
HIGH
SPIKE
RPD /tG/L
3.5
0.4
1.1
0.8
2.4
1.8
0.7
0.2
2.6
2.0
*
*
4.1
2.7
2.3
6.8
0.6
4.9
0.6
4.0
2.4
2.5
2.7
3.9
0.5
100
400
300
200
200
40
40
500
200
200
200
200
300
200
100
200
100
400
300
500
400
200
400
200
200
AVERAGE
RECOVERY
R(%)
104
105
112
95
101
103
105
103
104
106
103
105
107
102
104
101
105
109
110
107
107
104
109
102
110
S(R)
0.3
0.8
0.9
0.6
0.4
0.3
0.4
0.5
0.3
0.2
0.7
0.7
0.3
0.4
0.5
0.3
0.2
0.4
0.5
1.2
0.1
0.4
0.1
1.2
0.6
RPD
0.6
1.2
1.6
0.9
0.7
0.6
0.7
0.9
0.7
0.3
0.6
0.8
0.6
0.6
0.9
0.5
0.4
0.6
1.0
2.3
0.2
0.7
0.2
2.3
1.0
S(R) Standard deviation of percent recovery.
RPD Relative percent difference between duplicate spike determinations.
< Sample concentration below established method detection limit.
* Spike concentration <25% of sample background concentration.
200.15-42
Revision 1.2 May 1994
-------
TABLE 6. PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont.)
REGION 5 - TAP WATER
ANALYTE
Ag
Al
As
B
Ba
Be
Cd
Ce
Co
Cr
Cu
Fe
Hg
Li
Mn
Mo
Ni
Pb
Sb
Se
Sn
Ti
Tl
V
Zn
SAMPLE LOW
CONC SPIKE
/JG/L pG/L
<0.6
98.3
<3
26.8
30.2
<0.05
<0.4
<5
<0.6
<2
3.9
7.3
<3
4.4
0.26
<2
1.0
<4
<3
<5
<5
0.23
<6
<2
4.5
10.0
40.0
30.0
20.0
20.0
4.0
4.0
50.0
20.0
20.0
20.0
20.0
30.0
20.0
10.0
20.0
10.0
15.0
30.0
50.0
40.0
20.0
40.0
20.0
20.0
AVERAGE
RECOVERY
R(%)
114
108
110
104
105
110
106
108
108
105
92
98
103
108
108
107
108
98
117
101
119
109
108
105
111
S(R)
0.7
5.1
1.5
2.6
1.4
0.1
2.3
4.7
0.5
0.2
0.8
0.7
4.3
1.5
0.3
0.8
4.6
5.7
1.7
6.4
1.1
0.1
2.9
3.0
0.8
HIGH
SPIKE
RPD /iG/L
1.1
1.0
2.7
0.2
1.0
0.3
4.3
8.7
1.0
0.5
0.9
0.0
8.4
0.3
0.1
1.4
5.6
11.6
2.8
12.7
1.9
0.0
5.3
5.7
0.2
100
400
300
200
200
40
40 '
500
200
200
200
200
300
200
100
200
100
400
300
500
400
200
400
200
200
AVERAGE
RECOVERY
R(%)
109
111
114
99
104
108
106
106
107
108
104
108
104
106
107
105
106
112
114
114
114
108
110
105
113
S(R)
0.2
0.7
0.7
0.4
0.4
0.5
0.6
0.4
0.5
0.2
0.2
0.6
0.0
0.4
0.5
0.7
0.3
0.3
0.5
0.4
0.7
0.5
1.0
1.5
0.1
RPD
0.4
0.7
1.2
0.6
0.6
0.9
1.2
0.7
1.0
0.4
0.4
1.1
0.1
0.6
0.8
1.3
0.1
0.6
0.8
0.7
1.3
0.8
1.7
2.9
0.2
S(R) Standard deviation of percent recovery.
RPD Relative percent difference between duplicate spike determinations.
< Sample concentration below established method detection limit.
200.15-43
Revision 1.2 May 1994
-------
TABLE 6. PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont.)
REGION 6 - TAP WATER
ANALYTE
Ag
Al
As
B
Ba
Be
Cd
Ce
Co
Cr
Cu
Fe
Hg
Li
Mn
Mo
N1
Pb
Sb
Se
Sn
Ti
Tl
V
Zn
SAMPLE LOW
CONC SPIKE
pG/L 0G/L
<0.6
<4
5.2
98.7
18.0
0.07
<0.4
<5
<0.6
<2
2.1
<2
<3
34.4
1.5
52.7
<0.7
<4
<3
<5
6.1
2.5
<6
<2
3.6
10.0
40.0
30.0
20.0
20.0
4.0
4.0
50.0
20.0
20.0
20.0
20.0
30.0
20.0
10.0
20.0
10.0
15.0
30.0
50.0
40.0
20.0
40.0
20.0
20.0
AVERAGE
RECOVERY
R(%)
102
111
110
*
102
102
95
93
95
97
98
97
105
116
97
102
101
89
115
119
110
104
106
100
103
S(R)
1.0
3.8
8.6
*
1.0
0.7
2.9
3.0
1.6
1.0
1.8
2.0
1.2
2.4
1.1
7.6
2.0
8.7
0.3
0.3
7.9
0.9
3.8
3.3
1.2
HIGH
SPIKE
RPD /tG/L
2.0
6.8
10.7
*
0.7
1.3
6.1
6.5
3.3
2.1
2.3
3.3
2.2
0.7
1.9
2.1
4.1
19.5
0.6
0.5
6.6
1.4
7.1
6.5
1.7
100
400
300
200
200
40
40
500
200
200
200
200
300
200
100
200
100
400
300
500
400
200
400
200
200
AVERAGE
RECOVERY
R(%)
103
106
107
97
99
99
89
98
92
94
101
96
103
108
95
95
92
97
105
117
100
102
101
98
100
S(R)
0.3
0.3
1.4
0.5
0.1
0.3
0.6
0.4
0.4
0.4
0.4
0.6
0.8
0.3
0.3
0.9
0.8
0.1
0.7
1.1
2.3
0.2
0.5
0.5
0.2
RPD
0.6
0.5
2.5
0.3
0.1
0.6
1.3
0.9
0.9
0.8
0.7
1.3
1.6
0.3
0.7
0.9
1.8
0.2
1.4
1.9
4.4
0.3
0.9
1.1
0.3
S(R) Standard deviation of percent recovery.
RPD Relative percent difference between duplicate spike determinations.
< Sample concentration below established method detection limit.
* Spike concentration <10% of sample background concentration.
200.15-44
Revision 1.2 May 1994
-------
TABLE 6. PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont.)
REGION 10 - TAP WATER
ANALYTE
Ag
Al
As
B
Ba
Be
Cd
Ce
Co
Cr
Cu
Fe
Hg
Li
Mn
Mo
Ni
Pb
Sb
Se
Sn
Ti
Tl
V
Zn
SAMPLE LOW
CONC SPIKE
MG/L MG/L
<0.6
4.8
<3
24.4
10.7
<0.05
<0.4
<5
<0.6
<2
<2
11.0
<3
1.2
9.8
<2
<0.7
<4
<3
<5
7.3
0.39
8.2
<2
<0.5
10.0
40.0
30.0
20.0
20.0
4.0
4.0
50.0
20.0
20.0
20.0
20.0
30.0
20.0
10.0
20.0
10.0
15.0
30.0
50.0
40.0
20.0
40.0
20.0
20.0
AVERAGE
RECOVERY
R(%)
115
101
122
90
104
108
109
115
106
106
115
130
111
107
52
109
113
95
118
100
114
108
105
106
110
S(R)
0.5
3.7
5.5
1.9
0.8
0.7
1.9
1.1
0.6
0.2
0.5
1.6
3.3
1.7
0.8
1.2
2.0
1.7
3.3
2.7
3.5
0.7
6.4
2.5
0.0
HIGH
SPIKE
RPD /zG/L
0.9
4.4
9.0
1.4
1.0
1.2
3.4
1.9
1.1
0.5
0.9
1.6
6.0
1.8
1.6
2.3
3.5
3.5
5.6
5.4
2.7
1.2
7.2
4.7
0.0
100
400
300
200
200
40
40
500
200
200
200
200
300
200
100
200
100
400
300
500
400
200
400
200
200
AVERAGE
RECOVERY
R(%)
109
108
115
86
105
108
105
107
105
107
106
106
107
107
106
104
105
109
114
112
110
108
110
104
110
S(R)
0.6
0.5
0.4
1.0
0.4
0.2
0.4
0.1
0.3
0.3
0.4
0.1
1.1
0.9
0.1
0.2
0.4
0.9
0.1
1.2
1.4
0.1
1.4
0.4
0.3
RPD
1.1
0.7
0.6
2.1
0.8
0.4
0.7
0.2
0.5
0.5
0.7
0.0
2.0
1.7
0.2
0.4
0.8
1.7
0.1
2.1
2.4
0.1
2.4
0.9
0.5
S(R) Standard deviation of percent recovery.
RPD Relative percent difference between duplicate spike determinations.
< Sample concentration below established method detection limit.
200.15-45
Revision 1.2 May 1994
-------
TABLE 6. PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont.)
REGION 5 - RIVER WATER
ANALYTE
Ag
AT
As
B
Ba
Be
Cd
Ce
Co
Cr
Cu
SAMPLE LOW
CONC SPIKE
MG/L MG/L
<0.6
780
<3
38.8
51.7
0.12
<0.4
<5
1.8
<2
3.8
Fe 1240
Hg
Li
Mn
Mo
Ni
Pb
Sb
Se
Sn
Ti
Tl
V
Zn
<3
7.0
191
<2
5.5
8.0
3.5
<5
<5
3.9
<6
<2
16.8
5.0
20.0
15.0
10.0
10.0
2.0
2.0
25.0
10.0
10.0
10.0
10.0
15.0
10.0
5.0
10.0
5.0
7.5
15.0
25.0
20.0
10.0
20.0
10.0
10.0
AVERAGE
RECOVERY
R(%)
98
*
108
*
*
100
98
118
96
101
98
*
102
93
*
109
79
91
84
97
120
79
87
102
62
S(R)
2.0
*
3.7
*
*
0.8
1.3
3.0
1.8
0.5
2.6
*
0.7
14.9
*
3.0
13.5
45.8
5.3
1.4
3.5
13.4
0.5
0.0
3.5
HIGH
SPIKE
RPD /iG/L
4.1
*
6.8
*
*
0.5
2.5
5.1
1.8
1.0
1.5
*
1.3
4.9
*
5.5
7.4
9.4
0.6
2.9
5.9
2.6
1.2
0.0
2.2
50
200
150
100
100
20
20
250
100
100
100
100
150
100
50
100
50
200
150
250
200
100
200
100
100
AVERAGE
RECOVERY
R(%)
102
*
105
104
100
107
94
105
100
103
101
*
107
106
93
102
105
104
107
107
94
96
105
97
102
S(R)
0.8
*
1.0
3.6
1.3
2.0
1.5
0.9
0.8
0.8
0.8
*
1.5
1.7
10.4
1.2
1.7
2.1
0.9
2.7
2.5
1.4
0.7
0.8
0.4
RPD
1.6
*
2.0
1.5
0.9
3.7
3.2
1.8
1.6
1.6
1.4
*
2.8
1.5
3.7
2.3
2.2
2.4
1.4
5.1
5.4
1.0
1.2
1.5
0.6
S(R) Standard deviation of percent recovery.
RPD Relative percent difference between duplicate spike determinations.
< Sample concentration below established method detection limit.
* Spike concentration <25% of sample background concentration.
200.15-46
Revision 1.2 May 1994
-------
TABLE 7. AQUEOUS MATRIX ELEMENT CONCENTRATIONS0'
DRINKING WATER
REGION 2
MATRIX
ELEMENTS
Ca
K
Mg
Na
SiO,
Sr
MATRIX
ELEMENTS
Ca
K
Mg
Na
SiO,
Sr
SAMPLE
CONC
mg/L
4.08
0.786
0.626
7.83
3.09
0.029
REGION
SAMPLE
CONC
mg/L
253
4.60
36.3
39.9
32.6
4.06
%RSD
0.8
5.4
1.4
0.6
0.5
0.6
6
%RSD
n.a.
0.9
1.0
0.9
0.9
1.4
REGION 5
MATRIX
ELEMENTS
Ca
K
Mg
Na
Si02
Sr
MATRIX
ELEMENTS .
Ca
K
Mg
Na
SiO,
Sr
SAMPLE
CONC
mg/L
27.4
1.62
7.18
9.97
6.22
0.146
REGION
SAMPLE
CONC
mg/L
19.9
1.84
1.43
19.4
37.3
0.063
%RSD
0.9
1.8
0.9
0.4
1.0
0.6
10
%RSD
0.6
1.4
0.4
0.4
0.4
0.4
RIVER WATER
REGION 5
MATRIX
ELEMENTS
Ca
K
Mg
Na
SiO,
Sr
SAMPLE
CONC
mg/L
31.5
2.27
9.38
12.1
1.54
0.220
%RSD
1.1
1.2
1.6
0.9
18.4
1.5
(1) Mean sample concentration and relative standard deviation were,determined
from 5 replicate aliquots of each sample.
200.15-47
Revision 1.2 May 1994
-------
-------
METHOD 218.6
DETERMINATION OF DISSOLVED HEXAVALENT CHROMIUM
IN DRINKING WATER, GROUNDWATER, AND INDUSTRIAL WASTEWATER
EFFLUENTS BY ION CHROMATOGRAPHY
Revision 3.3
EMMC Version
E.J. Arar, S.E. Long (Technology Applications, Inc.), and J.D. Pfaff -
Method 218.6, Revision 3.2 (1991) '
E.J. Arar, J.D. Pfaff, and T.D. Martin - Method 218.6, Revision 3.3 (1994)
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
218.6-1
-------
METHOD 218.6
DETERMINATION OF DISSOLVED HEXAVALENT CHROMIUM IN DRINKING WATER,
GROUNDWATER, AND INDUSTRIAL WASTEWATER EFFLUENTS BY ION CHROMATOGRAPHY
1.0 SCOPE AND APPLICATION
1.1 This method provides procedures for determination of dissolved
hexavalent chromium (as Cr042") in drinking water, groundwater, and
industrial wastewater effluents.
Analyte
Chemical Abstracts Service
Registry Number (CASRN)
2-1
Hexavalent Chromium (as Cr04 )
11104-59-9
1.2 For reference where this method is approved for use in compliance
monitoring programs [e.g., Clean Water Act (NPDES) or Safe Drinking
Water Act (SDWA)] consult both the appropriate sections of the Code of
Federal Regulation (40 CFR Part 136 Table IB for NPDES, and Part 141
§ 141.23 for drinking water), and the latest Federal Register
announcements.
1.3 The method detection limits (MDL) obtained by a single laboratory for
hexavalent chromium (Cr(VI)) in the above matrices are listed in Table
1. The MDL obtained by an individual laboratory for a specific matrix
may differ from those listed depending on the nature of the sample and
the instrumentation used. A multilaboratory method detection limit
(MMDL) in reagent water was determined to be 0.4 jag/L. The IMDL was
based upon the within-laboratory standard deviation (sr) of thirteen
paired analyses of samples by thirteen laboratories at an average
analyte concentration of 1.4 /tg/L.
1.4 Samples containing high levels of anionic species such as sulphate and
chloride may cause column overload. Samples containing high levels of
organics or sulfides cause rapid reduction of soluble Cr(VI) to
Cr(III). Samples must be stored at 4°C and analyzed within 24 h of
collection.
1.5 This method should be used by analysts experienced in the use of ion
chromatography.
218.6-2
Revision 3.3 May 1994
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2.0 SUMMARY OF METHOD
2.1 An aqueous sample is filtered through a 0.45-/jm filter and the
filtrate is adjusted to a pH of 9 to 9.5 with a concentrated buffer
solution. A measured volume of the sample (50-250 #L) is introduced
into the ion chromatograph. A guard column removes organics from the
sample before the Cr(VI), as Cr042~, is separated on a high capacity
anion exchange separator column. Post-column derivatization of the
Cr(VI) with diphenylcarbazide is followed by detection of the colored
complex at 530 nm.
3.0 DEFINITIONS
3.1 Calibration Standard (CAL) - A solution prepared from the dilution of
stock standard solutions. The CAL solutions are used to calibrate the
instrument response with respect to analyte concentration (Sect. 7.9).
3.2 Dissolved Analyte - The concentration of analyte in an aqueous sample
that will pass through a 0.45-/zm membrane filter assembly prior to
sample acidification.
3.3 Instrument Performance Check (IPC) Solution - A solution of the method
analyte, used to evaluate the performance of the instrument system
with respect to a defined set of method criteria.
3.4 Laboratory Duplicates (LD1 and LD2) - Two aliquots of the same sample
taken in the laboratory and analyzed separately with identical
procedures. Analyses of LD1 and LD2 indicates precision associated
with laboratory procedures, but not with sample collection,
preservation, or storage procedures.
3.5 Laboratory Fortified Blank (LFB) - An aliquot of LRB to which known
quantities of the method analytes .are added in the laboratory. The
LFB is analyzed exactly like a sample, and its purpose is to determine
whether the methodology is in control and whether the laboratory is
capable of making accurate and precise measurements.
3.6 Laboratory Fortified Sample Matrix (LFM) - An aliquot of an
environmental sample to which a known quantity of the method analyte
is added in the laboratory. The LFM is analyzed exactly like a
sample, and its purpose is to determine whether the sample matrix
contributes bias to the analytical results. The background
concentration of the analyte in the sample matrix must be determined
in a separate aliquot and the measured value in the LFM corrected for
background concentration.
3.7 Laboratory Reagent Blank (LRB) - An aliquot of reagent water or other
blank matrices that are treated exactly as a sample including exposure
to all glassware, equipment, solvents, reagents, and internal
standards that are used with other samples. The LRB is used to
determine if the method analyte or other interferences are present in
the laboratory environment, reagents, or apparatus.
218.6-3 Revision 3.3 May 1994
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3.8 Linear Dynamic Range (LDR) - The concentration range over which the
instrument response to an analyte is linear.
3.9 Method Detection Limit (HDL) - The minimum concentration of an analyte
that can be identified, measured, and reported with 99% confidence
that the analyte concentration is greater than zero.
3.10 Quality Control Sample (QCS) - A solution of the method analyte of
known concentration which is used to fortify an aliquot of LRB or
sample matrix. The QCS is obtained from a source external to the
laboratory and different from the source of calibration standards. It
is used to check either laboratory or instrument performance.
3.11 Stock Standard Solution - A concentrated solution containing one or
more method analytes prepared in the laboratory using assayed
reference materials or purchased from a reputable commercial source.
4.0 INTERFERENCES
4.1 Interferences which affect the accurate determination of Cr(VI) may
come from several sources.
4.1.1 Contamination - A trace amount of Cr is sometimes found in
reagent grade salts. Since a concentrated buffer solution
is used in this method to adjust the pH of samples, reagent
blanks should be analyzed to assess for potential Cr(VI)
contamination. Contamination can also come from improperly
cleaned glassware or contact of caustic or acidic reagents
or samples with stainless steel or pigmented material.
4.1.2 Reduction of Cr(VI) to Cr(III) can occur in the presence of
reducing species in an acidic medium. At pH 6.5 or greater,
however, Cr042" which is less reactive than HCr04"is the
predominant species
4.1.3 Overloading of the analytical column capacity with high
concentrations of anionic species, especially chloride and
sulphate, will cause a loss of Cr(VI). The column specified
in this method can handle samples containing up to 5% sodium
sulphate or 2% sodium chloride2. Poor recoveries from
fortified samples and tailing peaks are typical
manifestations of column overload.
5.0 SAFETY
5.1 Hexavalent chromium is toxic and a suspected carcinogen and should be
handled with appropriate precautions. Extreme care should be
exercised when weighing the salt for preparation of the stock
standard. Each laboratory is responsible for maintaining a current
awareness file of OSHA regulations regarding the safe handling of
chemicals specified in this method. A reference file of material
218.6-4 Revision 3.3 May 1994
-------
safety data sheets should also be available to all personnel involved
in the chemical analysis.3'4
6.0 EQUIPMENT AND SUPPLIES
6.1 Ion Chromatograph
6.1.1 Instrument equipped with a pump capable of withstanding a
minimum backpressure of 2000 psi and of delivering a
constant flow in the range of 1-5 mL/min and containing no
metal parts in the sample, eluent or reagent flow path.
6.1.2 Helium gas supply (High purity, 99.995%).
6.1.3 Pressurized eluent container, plastic, 1- or 2-L size.
6.1.4 Sample loops of various sizes (50-250/iL).
6.1.5 A pressurized reagent delivery module with a mixing tee and
beaded mixing coil.
6.1.6 Guard Column - A column placed before the separator column
and containing a sorbent capable of removing strongly
absorbing organics and particles that would otherwise damage
the separator column (Dionex lonPac NG1 or equivalent).
6.1.7 Separator Column - A column packed with a high capacity
anion exchange resin capable of separating Cr042" from other
sample constituents (Dionex lonPac AS7 or equivalent).
6.1.8 A low-volume flow-through cell, visible lamp detector
containing no metal parts in contact with the eluent flow
path. Detection wavelength is at 530 nm.
6.1.9 Recorder, integrator or computer for receiving analog or
digital signals for recording detector response (peak height
or area) as a function of time.
6.2 Labware - All reusable labware (glass, quartz, polyethylene, Teflon,
etc.), including the sample containers, should be soaked overnight in
laboratory grade detergent and water, rinsed with water, and soaked
for 4 h in a mixture of dilute nitric and hydrochloric acid (1+2+9)
followed by rinsing with tap water and ASTM type I water.
NOTE: Chromic acid must not be used for cleaning glassware.
6.2.1 Glassware - Class A -VJilumetric flasks and a graduated
cylinder.
6.2.2 Assorted Class A calibrated pipettes.
6.2.3 10-mL male luer-lock disposable syringes.
218.6-5 Revision 3.3 May 1994
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6.2.4 0.45-/zm syringe filters.
6.2.5 Storage bottle - High density polypropylene, 1-L capacity.
6.3 Sample Processing Equipment
6.3.1 Liquid sample transport containers - High density
polypropylene, 125-mL capacity.
6.3.2 Supply of dry ice or refrigerant packing and styrofoam
shipment boxes.
6.3.3 pH meter - To read pH range 0-14 with accuracy + 0.03 pH
units.
6.3.4 0.45-/jm filter discs, 7.3-cm diameter (Gelman Aero BOA, Mfr.
No. 4262 or equivalent).
6.3.5 Plastic syringe filtration unit (Baxter Scientific, Cat. No.
1240 IN or equivalent).
7.0 REAGENTS AND STANDARDS
7.1 Reagents - All chemicals are ACS grade unless otherwise indicated.
7.1.1 Ammonium hydroxide, NH,OH, (sp.gr. 0.902),
(CASRN 1336-21-6).
7.1.2 Ammonium sulphate, (NH4)2304, (CASRN 7783-20-2).
7.1.3 1,5-Diphenylcarbazide, (CASRN 140-22-7).
7.1.4 Methanol, HPLC grade.
7.1.5 Sulfuric acid, concentrated (sp.gr. 1.84).
7.2 Reagent Water - For all sample preparations and dilutions, ASTM Type
I water (ASTM D1193) is required. Suitable water may be obtained by
passing distilled water through a mixed bed of anion and cation
exchange resins.
7.3 Cr(VI) Stock Standard Solution - To prepare a 1000 mg/L solution,
dissolve 4.501 g of Na2Cr04'4H20 in ASTM Type I water and dilute to 1
L. Transfer to a polypropylene storage container.
7.4 Laboratory Reagent Blank (LRB) - Aqueous LRBs can be prepared by
adjusting the pH of ASTM Type I water to 9-9.5 with the same volume of
buffer as is used for samples.
7.5 Laboratory Fortified Blank (LFB) - To an aliquot of LRB add an aliquot
of stock standard (Sect. 7.3) to produce a final concentration of 100
218.6-6 Revision 3.3 May 1994
-------
/jg/L of Cr(VI). The LFB must be carried through the entire sample
preparation and analysis scheme.
7.6 Quality Control Sample (QCS) - A quality control sample must be
obtained from an outside laboratory. Dilute an aliquot according to
instructions and analyze with samples. A recommended minimum
concentration for the QCS is 10 /jg/L.
7.7 Eluent - Dissolve 33 g of ammonium sulphate in 500 ml of ASTM type I
water and add 6.5 ml of ammonium hydroxide. Dilute to 1 L with ASTM
type I water.
7.8 Post-Column Reagent - Dissolve 0.5 g of 1,5-diphenylcarbazide in 100
ml of HPLC grade methanol. Add to about 500 ml of ASTM type I water
containing 28 ml of 98% sulfuric acid while stirring. Dilute with
ASTM type I water to 1 L in a volumetric flask. Reagent is stable for
four or five days but should be prepared only as needed.
7.9 Buffer Solution - Dissolve 33 g of ammonium sulphate in 75 ml of ASTM
type I water and add 6.5 ml of ammonium hydroxide. Dilute to 100 ml
with ASTM type I water.
8.0 SAMPLE COLLECTION. PRESERVATION. AND STORAGE
8.1 Prior to sample collection, consideration should be given to the type
of data required so that appropriate preservation and pretreatment
steps can be taken. Filtration and pH adjustment should be performed
at the time of sample collection or as soon thereafter as practically
possible.
8.2 For determination of dissolved Cr(VI), the sample should be filtered
through a 0.45-/mi filter. Use a portion of the sample to rinse the
syringe filtration unit and filter and then collect the required
volume of filtrate. Adjust the pH of the sample to 9-9.5 by adding
dropwise a solution of the buffer, periodically checking the pH with
the pH meter. Approximately 10 ml of sample are sufficient for three
1C analyses.
8.3 Ship and store the samples at 4°C. Bring to ambient temperature prior
to analysis. Samples must be analyzed within 24 h of collection.
9.0 QUALITY CONTROL
9.1 Each laboratory using this method is required to operate a formal
quality control (QC) program. The minimum requirements of this
program consist of an initial demonstration of laboratory capability,
and the analysis of laboratory reagent blanks, and fortified blanks
and samples as a continuing check on performance. The laboratory is
required to maintain performance records that define the quality of
the data thus generated.
9.2 Initial Demonstration of Performance (mandatory)
218.6-7 Revision 3.3 May 1994
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9.2.1 The initial demonstration of performance is used to
characterize instrument performance (MDLs and linear dynamic
range) and laboratory performance prior to sample analyses.
9.2.2 Method detection limit (MDL) — A MDL should be established
using reagent water fortified at a concentration of two-five
times the estimated detection limit. To determine the MDL
value, take seven replicate aliquots of the fortified
reagent water and process through the entire analytical
method. Perform all calculations defined in the method and
report the concentration values in the appropriate units.
Calculate the MDL as follows:
MDL = (t) X (s)
where: t = Student's t value for n-1 degrees
of freedom at the 99% confidence level;
t = 3.143 for six degrees of freedom.
s = standard deviation of the replicate
analyses.
The MDL must be sufficient to detect Cr (VI) at the required
level according to compliance monitoring regulation (Sect.
1.2). The MDL should be determined annually, when a new
operator begins work or whenever there is a change in
instrument analytical hardware or operating conditions.
9.2.3 Linear dynamic range (LDR) — The LDR should be determined
by analyzing a minimum of 7 calibration standards ranging in
concentration from 1 /zg/L to 5,000 //g/L across all
sensitivity settings of the spectrophotometer. Normalize
responses by dividing the response by the sensitivity
setting multiplier. Perform the linear regression of
normalized response vs. concentration and obtain the
constants m and b, where m is the slope of the line and b is
the y-intercept. Incrementally analyze standards of higher
concentration until the measured absorbance response, R, of
a standard no longer yields a calculated concentration, C ,
that is ± 10% of the known concentration, C, where C = (R°-
b)/m. That concentration defines the upper limit0of the
LDR for your instrument and analytical operating conditions.
Samples having a concentration that is > 90% of the upper
limit of the LDR must be diluted to fall within the bounds
of the current calibration curve concentration range and
reanalyzed.
9.3 Assessing Laboratory Performance (mandatory)
9.3.1 The laboratory must analyze at least one LRB (Sect. 7.4)
with each set of samples. Reagent blank data are used to
assess contamination from a laboratory environment. If the
218.6-8 Revision 3.3 May 1994
-------
Cr(VI) value in the reagent blank exceeds the determined
MDL, then laboratory or reagent contamination should be
suspected. Any determined source of contamination should be
corrected and the samples reanalyzed.
9.3.2 The laboratory must analyze at least one LFB (Sect. 7.5)
with each set of samples. Calculate accuracy as percent
recovery (Sect. 9.4.2). If the recovery of Cr(VI) falls
outside the control limits (Sect. 9.3.3), then the procedure
is judged out of control, and the source of the problem
should be identified and resolved before continuing the
analysis.
9.3.3 Until sufficient data become available (usually a minimum of
20 to 30 analyses), assess laboratory performance against
recovery limits of 90-110%. When sufficient internal
performance data becomes available, develop control limits
from the percent mean recovery (x) and the standard
deviation (s) of the mean recovery. These data are used to
establish upper and lower control limits as follows:
UPPER CONTROL LIMIT = x + 3s
LOWER CONTROL LIMIT = x - 3s
9.3.4 To verify that the instrument is properly calibrated on a
continuing basis, run a LRB and a IPC (Sect. 3.3) after
every ten analyses. The results of analyses of standards
will indicate whether the calibration remains valid. If the
measured concentration of the IPC (a midpoint calibration
standard) deviates from the true concentration by more than
+5%, perform another analysis of the LPC. If the
discrepancy is still +5% of the known concentration then the
instrument must be recalibrated and the previous ten samples
reanalyzed. The instrument response from the calibration
check may be used for recallbration purposes.
9.3.5 Quality control sample (QCS) - Each quarter, the laboratory
should analyze one or more QCS. If criteria provided with
the QCS are not within ±10% of the stated value, corrective
action must be taken and documented.
9.4 Assessing Analyte Recovery and Data Quality
9.4.1 The laboratory must add a known amount of Cr(VI) to a
minimum of 10% of samples. The concentration level can be
the same as that of the laboratory fortified blank
(Sect. 7.5). ,
9.4.2 Calculate the percent recovery for Cr(VI) corrected for
background concentration measured in the unfortified sample,
and compare this value to the control limits established in
Sect. 9.3.3 for the analysis of LFBs. Fortified recovery
218.6-9 Revision 3.3 May 1994
-------
calculations are not required if the concentration of Cr(VI)
added is less than 2X the sample background concentration.
Percent recovery may be calculated in units appropriate to
the matrix, using the following equation:
CF - C
R = X 100
F
where:
R = percent recovery
CF= fortified sample concentration
C = sample background concentration
F = concentration equivalent of Cr(VI) added to sample
9.4.3 If the recovery of Cr(VI) falls outside control limits
established in Section 9.3.3 and the recovery obtained for
the LFB was shown to be in control (Sect. 9.3), the recovery
problem encountered with the fortified sample is judged to
be matrix related, not system related. The result for
Cr(VI) in the unfortified sample must be labelled 'suspect
matrix'.
10.0 CALIBRATION AND STANDARDIZATION
10.1 Establish 1C operating conditions as indicated in Table 2. The flow
rate of the eluent pump is set at 1.5 mL/min and the pressure of the
reagent delivery module adjusted so that the final flow rate of the
post column reagent (Sect. 7.8) from the detector is 2.0 mL/min. This
requires manual adjustment and measurement of the final flow rate
using a graduated cylinder and a stop watch. A warm up period of
approximately 30 min after the flow rate has been adjusted is
recommended and the flow rate should be checked prior to calibration
and sample analysis.
10.2 Injection sample loop size should be chosen based on anticipated
sample concentrations and the selected sensitivity setting of the
spectrophotometer. A 250-/iL loop was used to establish the method
detection limits in Table 1. A 50-/tL loop is normally sufficient for
higher concentrations. The sample volume used to load the sample loop
should be at least 10 times the loop size so that all tubing in
contact with sample is thoroughly flushed with new sample to minimize
cross-contamination.
10.3 Before using the procedure (Section 11.0) to analyze samples, there
must be data available documenting initial demonstration of
performance. The required data and procedure is described in Section
9.2. This data must be generated using the same instrument operating
conditions and calibration routine to be used for sample analysis.
218.6-10 Revision 3.3 May 1994
-------
These documented data must be kept on file and be available for review
by the data user.
10.4 The recommended calibration routine is given in Section 11.3.
11.0 PROCEDURE
11.1 Filtered, pH adjusted samples at 4°C should be brought to
ambient temperature prior to analysis.
11.2 Initiate instrument operating configuration described in Section 10
and Table 2.
11.3 Calibration - Before samples are analyzed a calibration should be
performed using a minimum of three calibration solutions that bracket
the anticipated concentration range of the samples. Calibration
standards should be prepared from the stock standard (Sect. 7.3) by
appropriate dilution with ASTM type I water (Sect. 7.2) in volumetric
flasks. The solution should be adjusted to pH 9-9.5 with the buffer
solution (Sect. 7.9) prior to final dilution.
11.4 Construct a calibration curve of analyte response (peak height or
area) versus analyte concentration over a concentration range of one
or two orders of magnitude. The calibration range should bracket the
anticipated concentration range of samples. The coefficient of
correlation (r) for the curve should be 0.999 or greater.
11.5 Draw into a new, unused syringe (Sect. 6.2.3) approximately 3 ml of
sample. Inject 10X the volume of the sample loop into the injection
valve of the 1C. Sample concentrations that exceed the calibration
range must be diluted and reanalyzed.
11.6 During the analysis of samples, the laboratory must comply with the
required quality control described in Sections 9.3 and 9.4.
12.0 DATA ANALYSIS AND CALCULATIONS
12.1 The sample concentration can be calculated from the calibration curve.
Report values in /jg/L. Sample concentrations must be corrected for
any Cr(VI) contamination found in the LRB.
12.2 The QC data obtained during sample analyses provide an indication of
the quality of sample data and should be reported with sample results.
13.0 METHOD PERFORMANCE
13.1 Instrumental operating conditions used for single-laboratory testing
of the method are summarized in Table 2. MDLs for dissolved Cr(VI) in
five matrix waters are listed in Table 1.
13.2 Single-analyst precision and accuracy data for five matrix waters,
drinking water, deionized water, groundwater, treated municipal sewage
218.6-11 Revision 3.3 May 1994
-------
wastewater, and treated electroplating wastewater are listed in Table
3.
13.3 Pooled Precision and Accuracy: This method was tested by 21
volunteer laboratories in a joint study by the USEPA and the
American Society for Testing and Materials (ASTM). Mean
recovery and accuracy for Cr(VI) (as Cr042") was determined
from the retained data of 13 laboratories in reagent water,
drinking water, ground water, and various industrial
wastewaters. For reagent water, the mean recovery and the
overall, and single-analyst relative standard deviations
were 105%, 7.8% and 3.9% respectively. For the other
matrices combined, the same values were 96.7%, 11.9% and
6.3%, respectively. Table 4 contains the linear equations
that describe the single-analyst standard deviation, overall
standard deviation and mean recovery of Cr(VI) in reagent
water and matrix water.
14.0 POLLUTION PREVENTION
14.1 Pollution prevention encompasses any technique that reduces or
eliminates the quantity or toxicity of waste at the point of
generation. Numerous opportunities for pollution prevention exist in
laboratory operation. The EPA has established a preferred hierarchy
of environmental management techniques that places pollution
prevention as the management option of first choice. Whenever
feasible, laboratory personnel should use pollution prevention
techniques to address their waste generation. When wastes cannot be
feasibly reduced at the source, the Agency recommends recycling as the
next best option.
14.2 For information about pollution prevention that may be applicable to
laboratories and research institutions, consult Less is Better:
Laboratory Chemical Management for Waste Reduction, available from the
American Chemical Society's Department of Government Relations and
Science Policy, 1155 16th Street N.W., Washington D.C. 20036,
(202)872-4477.
15.0 WASTE MANAGEMENT
15.1 The Environmental Protection Agency requires that laboratory waste
management practices be conducted consistent with all applicable rule
and regulations. The Agency urges laboratories to protect the air,
water, and land by minimizing and controlling all releases from hoods
and bench operations, complying with the letter and spirit of any
sewer discharge permits and regulations, and by complying with all
solid and hazardous waste regulations, particularly the hazardous
waste identification rules and land disposal restrictions. For
further information on waste management consult The Waste Management
Manual for Laboratory Personnel, available from the American Chemical
Society at the address listed in the Sect. 14.2.
218.6-12 Revi si on 3.3 May 1994
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16.0 REFERENCES
1. Glaser, J.A., Foerst, D.L., McKee, G.D., Quave, S.A. and Budde, W.L.,
"Trace Analyses for Wastewaters", Environ. Sci. and Technol.. Vol.15,
No.12, 1981, pp.1426-1435.
2. Dionex Technical Note No. 26, May 1990.
3. "Proposed OSHA Safety and Health Standards, Laboratories,"
Occupational Safety and Health Administration, Federal Register, July
24, 1986.
4. "OSHA Safety and Health Standards, General Industry," (29 CFR 1910),
Occupational Safety and Health Administration, OSHA 2206, revised
January 1976.
218.6-13 Revision 3.3 May 1994
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17.0 TABLES. DIAGRAMS. FLOWCHARTS AND VALIDATION DATA
TABLE 1. METHOD DETECTION LIMIT FOR CR(VI)
Matrix Tvoe
Reagent Water
Drinking Water
Ground Water
Primary Sewage
Cone. Used to Compute MDL
uq/L
1
2
2
2
MDL
ua/l
0.4
0.3
0.3
0.3
wastewater
Electroplating
wastewater
0.3
TABLE 2. ION CHROMATOGRAPHIC CONDITIONS
Columns: Guard Column - Dionex lonPac NG1
Separator Column - Dionex lonPac AS7
Eluent: 250 mM (NH,)2SO,
100 mM NH4OH
Flow rate =1.5 mL/min
Post-Column Reagent: 2mM Diphenylcarbohydrazide
10% v/v CH,OH
1 N H2S04
Flow rate =0.5 mL/min
Detector: Visible 530 nm
Retention Time: 3.8 min
218.6-14
Revision 3.3 May 1994
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TABLE 3. SINGLE ANALYST PRECISION AND ACCURACY
Cr(VI)
Sample Type (#g/L) (a)
Reagent Water
Drinking Water
Groimdwater
Primary sewage
wastewater
effluent
Electroplating
wastewater
effluent
100
1000
100
1000
100
1000
100
1000
100
1000
Mean Recovery (%) RPD (b)
100
100
105
98
98
96
100
104
99
101
0.8
0.0
6.7
1.5
0.0
0.8
0.7
2.7
0.4
0.4
(a) Sample fortified at this concentration level.
(b) RPD - relative percent difference between duplicates.
TABLE 4. SINGLE-ANALYST PRECISION, OVERALL PRECISION AND RECOVERY
FROM MULTILABORATORY STUDY
Reagent Water Matrix Water
(6-960 jug/L) (6-960 /jg/L)
Mean Recovery X = 1.020C + 0.592 X = 0.989C - 0.411
Overall Standard SR = 0.035X +0.893 SR = 0.059X + 1 055
Deviation
Single-Analyst sr = 0.021X + 0.375 s = 0.041X + 0.393
Standard Deviation
X Mean concentration, /zg/L, exclusive of outliers.
C True value, /*g/L.
SR Overall standard deviation.
sr Single-analyst standard deviation.
218.6-15 Revision 3.3 May 1994
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METHOD 245.1
DETERMINATION OF MERCURY IN WATER
BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY
Revision 3.0
EMMC Version
J.F. Kopp, M.C. Longbottom, and L.B. Lobring - Mercury in Water (Cold Vapor
Technique), Revision 1.0, (1972)
J.F. Kopp and L.B. Lobring - Method 245.1, Revision 2.0 (1979)
L.B. Lobring and B.B. Potter - Method 245.1, Revision 2.3 (1991)
J.W. O'Dell, B.B. Potter, L.B. Lobring, and T.D. Martin - Method 245.1,
Revision 3.0 (1994)
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
245.1-1
-------
METHOD 245.1
DETERMINATION OF MERCURY IN WATER
BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY
1.0 SCOPE AND APPLICATION
1.1 This procedure1 measures total mercury (organic + inorganic) in
drinking, surface, ground, sea, brackish waters, industrial and
domestic wastewater.
Chemical Abstracts Service
Analyte Registry Number (CASRN)
Mercury 7439-97-6
1.2 The range of the method is 0.2 to 10 ^g Hg/L. The range may be
extended above or below the normal range by increasing or decreasing
sample size. However, the actual method detection limit and linear
working range will be dependent on the sample matrix, type of
instrumentation configuration, and selected operating conditions.
1.3 Reduced volume or semi-automated versions of this method, that use fa
same reagents and molar ratios, are acceptable provided they meet the
quality control and performance requirements stated in the method
(Sect. 9.0).
1.4 For reference where this method is approved for use in compliance
monitoring programs [e.g., Clean Water Act (NPDES) or Safe Drinking
Water Act (SDWA)] consult both the appropriate sections of the Code of
Federal Regulation (40 CFR Part 136 Table IB for NPDES, and Part 141
§ 141.23 for drinking water), and the latest Federal Register
announcements.
2.0 SUMMARY OF METHOD
2.1 A known portion of a water sample is transferred to a BOD bottle,
equivalent ground glass stoppered flask or other suitable closed
container. It is digested in diluted potassium permanganate-potassium
persulfate solutions and oxidized for 2 h at 95°C. Mercury in the
digested water sample is reduced with stannous chloride to elemental
mercury and measured by the conventional cold vapor atomic absorption
technique.
245.1-2 Revision 3.0 May 1994
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3.0 DEFINITIONS
3.1 Calibration Blank - A volume of reagent water acidified with the same
acid matrix as in the calibration standards. The calibration blank is
a zero standard and is used to auto-zero the instrument.
3.2 Calibration Standard (CAL) - A solution prepared from the dilution of
stock standard solutions. The CAL solutions are used to calibrate the
instrument response with respect to analyte concentration.
3.3
Field Reagent Blank (FRB) - An aliquot of reagent water or other blank
matrix that is placed in a sample container in the laboratory and
treated as a sample in all respects, including shipment to the
sampling site, exposure to the sampling site conditions, storage,
preservation, and all analytical procedures. The purpose of the FRB
is to determine if method analytes or other interferences are present
in the field environment.
3.4 Instrument Performance Check (IPC) Solution - A solution of the method
analyte, used to evaluate the performance of the instrument system
with respect to a defined set of method criteria.
3.5 Laboratory Duplicates (LD1 and LD2) - Two aliquots of the same sample
taken in the laboratory and analyzed separately with identical
procedures. Analyses of LD1 and LD2 indicates precision associated
with laboratory procedures, but not with sample collection,
preservation, or storage procedures.
3.6 Laboratory Fortified Blank (LFB) - An aliquot of LRB to which a known
quantity of the method analyte is added in the laboratory. The LFB is
analyzed exactly like a sample, and its purpose is to determine
whether the methodology is in control and whether the laboratory is
capable of making accurate and precise measurements.
3.7 Laboratory Fortified Sample Matrix (LFM) - An aliquot of an
environmental sample to which a known quantity of the method analyte
is added in the laboratory. The LFM is analyzed exactly like a
sample, and its purpose is to determine whether the sample matrix
contributes bias to the analytical results. The background
concentrations of the analytes in the sample matrix must be determined
in a separate aliquot and the measured values in the LFM corrected for
background concentrations.
3.8 Laboratory Reagent Blank (LRB) - An aliquot of reagent water or other
blank matrices that are treated exactly as a sample including exposure
to all glassware, equipment, solvents, reagents, and internal
standards that are used with other samples. The LRB is used to
determine if the method analyte or other interferences are present in
the laboratory environment, reagents, or apparatus.
3.9 Linear Dynamic Range (LDR) - The concentration range over which the
instrument response to an analyte is linear.
245.1-3 Revision 3.0 May 1994
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3.10 Method Detection Limit (MDL) - The minimum concentration of an analyte
that can be identified, measured, and reported with 99% confidence
that the analyte concentration is greater than zero.
3.11 Quality Control Sample (QCS) - A solution of the method analyte of
known concentration which is used to fortify an aliquot of LRB or
sample matrix. The QCS is obtained from a source external to the
laboratory and different from the source of calibration standards. It
is used to check either laboratory or instrument performance.
3.12 Standard Addition - The addition of a known amount of analyte to the
sample in order to determine the relative response of the detector to
an analyte within the sample matrix. The relative response is then
used to assess either an operative matrix effect or the sample analyte
concentration.
3.13 Stock Standard Solution - A concentrated solution containing one or
more method analytes prepared in the laboratory using assayed
reference materials or purchased from a reputable commercial source.
4.0 INTERFERENCES
4.1 Interferences have been reported for waters containing sulfide,
chloride, copper and tellurium. Organic compounds which have broad
band UV absorbance (around 253.7 nm) are confirmed interferences. The
concentration levels for interferants are difficult to define. This
suggests that quality control procedures (Sect. 9) must be strictly
followed.
4.2 Volatile materials (e.g. chlorine) which absorb at 253.7 nm will cause
a positive interference. In order to remove any interfering volatile
materials, the dead air space in the digestion vessel (BOD bottle)
should be purged before addition of stannous chloride solution.
4.3 Low level mercury sample preparation, digestion, and analysis may be
subject to environmental contamination if preformed in areas with hflp
ambient backgrounds where mercury was previously employed as an
analytical reagent in analyses such as total Kjeldahl nitrogen (TKN)
or chemical oxygen demand (COD).
5.0 SAFETY
5.1 The toxicity and carcinogenicity of each reagent used in this method
has not been fully established. Each chemical should be regarded as
a potential health hazard and exposure to these compounds should be
minimized by good laboratory practices. Normal accepted laboratory
safety practices should be followed during reagent preparation and
instrument operation. Always wear safety glasses or full-face shield
for eye protection when working with these reagents. Each laboratory
is responsible for maintaining a current safety plan, a current
awareness file of OSHA regulations regarding the safe handling of the
chemicals specified in this method. '
245.1-4 Revision 3.0 May 1994
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5.2 Mercury compounds are highly toxic if swallowed, inhaled, or absorbed
through the skin. Analyses should be conducted in a laboratory
exhaust hood. The analyst should use chemical resistant gloves when
handling concentrated mercury standards.
5.3 The acidification of samples containing reactive materials may result
in the release of toxic gases, such as cyanides or sulfides.
Acidification of samples should be done in a fume hood.
5.4 All personnel handling environmental samples known to contain or to
have been in contact with human waste should be immunized against
known disease causative agents.
6.0 EQUIPMENT AND SUPPLIES
6.1 Atomic Absorption Cold Vapor System
6.1.1 Atomic Absorption Spectrophotometer - Any atomic absorption
unit having an open sample presentation area in which to
mount the absorption cell is suitable. Instrument settings
recommended by the particular manufacturer should be
followed. The use of background correction is recommended,
but is not mandatory.
6.1.2 Mercury Hollow Cathode Lamp - Single element hollow cathode
lamp or electrodeless discharge lamp and associated power
supply.
6.1.3 Absorption Cell - Standard spectrophotometer cells 10-cm
long, having quartz windows may be used. Suitable cells may
be constructed from plexiglass tubing, 1-in. O.D. by 4 1/2-
in. long. The ends are ground perpendicular to the
longitudinal axis and quartz windows (1-in. diameter by
1/16-in. thickness) are cemented in place. Gas inlet and
outlet ports (also of plexiglass but 1/4-in. O.D.) are
attached approximately 1/2-in. from each end. The cell is
strapped to a burner for support and aligned in the light
beam to give the maximum transmittance.
6.1.4 Aeration Tubing - Inert mercury-free tubing is used for
passage of mercury vapor from the sample bottle to the
absorption cell. In some systems, mercury vapor is
recycled. Straight glass tubing terminating in a coarse
porous glass aspirator is used for purging mercury released
from the water sample in the BOD bottle.
6.1.5 Air Pump - Any pump (pressure or vacuum system) capable of
passing air 1 L/min is used. Regulated compressed air can
be used in an open one-pass system.
6.1.6 Drying Tube - Tube (6-in. x 3/4-in. OD) containing 20 g of
magnesium perchlorate. The filled tube is inserted (in-
245.1-5 Revision 3.0 May 1994
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line) between the BOD bottle and the absorption tube. In
place of the magnesium perchlorate drying tube, a small
reading lamp is positioned to radiate heat (about 10°C above
ambient) on the absorption cell. Heat from the lamp
prevents water condensation in the cell.
6.1.7 Recorder - Any multi-range variable speed recorder or data
system that is compatible with the UV detection system is
suitable.
Note: Instruments designed specifically for mercury measurement
using the cold vapor technique are commercially available
and may be substituted for the atomic absorption cold vapor
system described above.
6.2 Flowmeter, capable of measuring an air flow of 1 L/min.
6.3 A water bath with a covered top and capacity to maintain a water depth
of 2 to 3 inches at 95°C.
6.4 Analytical balance, with capability to measure to 0.1 mg, for use in
weighing reagents and preparing standards.
6.5 Labware - All reusable labware should be sufficiently clean for the
task objectives. Particular attention should be given to all ground
glass surfaces during cleaning. Routinely all items should be soaked
in 30% HN03 and rinsed three times in reagent water. Digestion
containers used in sample preparation that do not rinse clean of the
previous sample should be washed with a detergent solution prior to
acid cleaning.
6.5.1 Glassware - Volumetric flasks and graduated cylinders.
6.5.2 BOD bottles (or other equivalent suitable closed
containers).
6.5.3 Assorted calibrated pipettes.
7.0 REAGENTS AND STANDARDS
7.1 Reagents may contain elemental impurities which bias analytical
results. All reagents should be assayed by the chemical
manufacturer for mercury and meet ACS specifications. The assayed
mercury level of all solid reagents used in this method should
not exceed 0.05 ppm. It is recommended that the laboratory
analyst assay all reagents for mercury.
7.2 Reagent Water, ASTM type II5.
7.3 Nitric Acid (HN03), concentrated (sp.gr. 1.41), assayed mercury level
is not to exceed 1 #9/1..
245.1-6 Revision 3.0 May 1994
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7.3.1 Nitric acid (1+1) - Add 500 ml concentrated HN03 to 400 ml
reagent water and dilute to 1 L.
7.4 Sulfuric Acid (H2S04), concentrated (sp.gr. 1.84), assayed mercury
level is not to exceed 1 /jg/L.
7.4.1 Sulfuric acid, 0.5 N - Slowly add 14.0 ml of cone. H2S04 to
500 ml of reagent water and dilute to 1 L with reagent water.
7.5 Mercury standard, stock, 1 ml = 100 fig Hg: DO NOT DRY. CAUTION:
highly toxic element. Dissolve 0.1354 g HgCl2 in 75 ml reagent water.
Add 50.0 mL concentrated HN03 (Sect. 7.3) and dilute to volume in 1-L
volumetric flask with reagent water.
7.6 Mercury calibration standard (CAL) - To each volumetric flask used for
serial dilutions, acidify with (0.1 to 0.2% by volume) HN03 (Sect. 7.3).
Using mercury stock standard (Sect. 7.5), make serial dilutions to
obtain a concentration of 0.1 /jg Hg/mL.
7.7 Potassium permanganate solution - Dissolve 5 g of KMn04 in 100 ml of
reagent water.
7.8 Potassium persulfate solution - Dissolve 5 g of K2S208 in 100 ml of
reagent water.
7.9 Sodium chloride-hydroxylammonium chloride solution - Dissolve 12 g of
NaCl and 12 g of hydroxylamine hydrochloride (NH2OH'HC1) in 100 ml
reagent water. (Hydroxylamine sulfate (NH2OH)2'H2S04 may be used in place
of hydroxylamine hydrochloride.)
7.10 Stannous chloride solution - Add 25 g of SnCl?'2H20 to 250 ml of 0.5 N
H2S04 (Sect. 7.4.1). This mixture is a suspension and should be stirred
continuously during use.
7.11 Blanks - Three types of blanks are required for the analysis. The
calibration blank is used in establishing the analytical curve, the
laboratory reagent blank is used to assess possible contamination from
the sample preparation procedure, and the laboratory fortified blank
is used to assess routine laboratory performance.
7.11.1 The calibration blank must contain all reagents in the same
concentrations and in the same volume as used in preparing the
calibration solutions.
7.11.2 The laboratory reagent blank (LRB) is prepared in the manner
as the calibration blank except the LRB must be carried
through the entire sample preparation scheme.
7.11.3 The laboratory fortified blank (LFB) is prepared by fortifying
a sample size volume of laboratory reagent blank solution with
mercury to a suitable concentration of > 10X the MDL, but <
245.1-7 Revision 3.0 May 1994
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the midpoint concentration of the calibration curve. The LFB
must be carried through the entire sample preparation scheme.
7.12 Instrument Performance Check (IPC) Solution - The IPC solution is used
to periodically verify instrument performance during analysis. It
must contain all reagents in the same concentration as the calibration
solutions and mercury at an appropriate concentration to approximate
the midpoint of the calibration curve. The IPC solution should be
prepared from the same CAL standard (Sect. 7.6) as used to prepare the
calibration solutions. Agency programs may specify or request that
additional instrument performance check solutions be prepared at
specified concentrations in order to meet particular program needs.
7.13 Quality Control Sample (QCS) - For initial and periodic verification
of calibration standards and instrument performance, analysis of a QCS
is required. The QCS must be obtained from an outside source
different from the standard stock solution, but prepared in the same
manner as the calibration solutions. The concentration of the mercury
in the QCS solution should be such that the resulting solution will
provide an absorbance reading near the midpoint of the calibration
curve. The QCS should be analyzed quarterly or more frequently as
needed to meet data-quality needs.
8.0 SAMPLE COLLECTION. PRESERVATION. AND STORAGE
8.1 Because of the extreme sensitivity of the analytical procedure and the
presence of mercury in a laboratory environment, care must be taken to
avoid extraneous contamination. Sampling devices, sample containers
and plastic items should be determined to be free of mercury; the
sample should not be exposed to any condition in the laboratory that
may result in contamination from airborne mercury vapor.
8.2 For the determination of total mercury (inorganic + organic) in
aqueous samples, samples are not filtered, but acidified with (1+1)
nitric acid (Sect. 7.3.1) to pH < 2 (normally, 3 ml of (1+1) acid per
liter of sample is sufficient for most ambient and drinking water
samples). Preservation may be done at the time of collection,
however, to avoid the hazards of strong acids in the field, transport
restrictions, and possible contamination it is recommended that the
samples be returned to the laboratory as soon as possible after
collection and acid preserved upon receipt in the laboratory.
Following acidification, the sample should be mixed, held for sixteen
hours, and then verified to be pH < 2 just prior withdrawing an
aliquot for processing. If for some reason such as high alkalinity
the sample pH is verified to be > 2, more acid must be added and the
sample held for additional sixteen hours until verified to be pH < 2.
The preserved sample should be analyzed within 28 days of collection.
NOTE: When the nature of the sample is either unknown or is known to
be hazardous, acidification should be done in a fume hood.
See Section 5.2.
245.1-8 Revision 3.0 May 1994
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8.3 A field blank should be prepared and analyzed as required by the data
user. Use the same container and acid as used in sample collection.
9.0 QUALITY CONTROL
9.1 Each laboratory using this method is required to operate a formal
quality control (QC) program. The minimum requirements of this
program consist of an initial demonstration of laboratory capability
by analysis of laboratory reagent blanks, fortified blanks and samples
used for continuing check on method performance. Commercially
available water quality control samples are acceptable for routine
laboratory use. The laboratory is required to maintain performance
records that define the quality of the data generated.
9.2 Initial Demonstration of Performance (mandatory).
9.2.1 The initial demonstration of performance is used to
characterize instrument performance (determination of linear
dynamic ranges and analysis of quality control samples) and
laboratory performance (determination of method detection
limits) prior to analyses conducted by this method.
9.2.2 Linear dynamic range (LDR) - The upper limit of the LDR must
be established. It must be determined from a linear
calibration prepared from a minimum of three different
concentration standards, one of which is close to the upper
limit of the linear range. The LDR should be determined by
analyzing succeedingly higher standard concentrations of
mercury until the observed analyte concentration is no more
than 10% below the stated concentration of the standard. The
determined LDR must be documented and kept on file. The LDR
which may be used for the analysis of samples should be judged
by the analyst from the resulting data. Determined sample
analyte concentrations that are greater than 90% of the
determined upper LDR limit must be diluted and reanalyzed.
The LDR should be verified annually or whenever, in the
judgement of the analyst, a change in analytical performance
caused by either a change in instrument hardware or operating
conditions would dictate they be redetermined.
9.2.3 Quality control sample (QCS) - When beginning the use of this
method, on a quarterly basis, after the preparation of stock or
calibration standard solutions or as required to meet data-
quality needs, verify the calibration standards and acceptable
instrument performance with the preparation and analyses of a
QCS (Sect. 7.13). To verify the calibration standards, the
determined concentration of the QCS must be within ± 10% of the
stated value. If the calibration standard cannot be verified,
performance of the determinative step of the method is
unacceptable. The source of the problem must be identified and
corrected before either proceeding on with the initial
245.1-9 Revision 3.0 May 1994
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determination of method detection limits or continuing with on-
going analyses.
9.2.4 Method detection limit (MDL) - A mercury MDL must be
established using an LRB solution fortified at a concentration
of two to three times the estimated detection limit. To
determine MDL values, take seven replicate aliquots of the
fortified LRB and process through the entire analytical method.
Perform all calculations defined in the method and report the
concentration values in the appropriate units. Calculate the
MDL as follows:
MDL = (t) x (S)
where: t = students' t value for a 99% confidence level and
a standard deviation estimate with n-1 degrees of
freedom [t = 3.14 for seven replicates].
S = standard deviation of the replicate analyses.
Note: If the relative standard deviation (RSD) from the
analyses of the seven aliquots is < 10%, the
concentration used to determine the mercury MDL may
have been inappropriately high for the determination.
If so, this could result in the calculation of an
unrealistically low MDL. Concurrently, determination
of MDL in an LRB solution represents a best case
situation and does not reflect possible matrix effects
of real world samples. However, successful analyses of
LFMs (Sect. 9.4) can give confidence to the MDL value
determined in LRB solution.
The MDL must be sufficient to detect mercury at the required
level according to compliance monitoring regulation (Sect.
1.2). The mercury MDL should be determined annually, when a
new operator begins work or whenever, in the judgement of the
analyst, a change in analytical performance caused by either a
change in instrument hardware or operating conditions would
dictate they be redetermined.
9.3 Assessing Laboratory Performance (mandatory)
9.3.1 Laboratory reagent blank (LRB) - The laboratory must analyze at
least one LRB (Sect. 7.11.2) with each batch of 20 or fewer
samples of the same matrix. LRB data are used to assess
contamination from the laboratory environment. LRB values that
exceed the MDL indicate laboratory or reagent contamination
should be suspected. When LRB values constitute 10% or more of
the analyte level determined for a sample or is 2.2 times the
analyte MDL whichever is greater, fresh aliquots of the samples
must be prepared and analyzed again for the affected analytes
245.1-10 Revision 3.0 May 1994
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after the source of contamination has been corrected and
acceptable LRB values have been obtained.
9.3.2 Laboratory fortified blank (LFB) - The laboratory must analyze
at least one LFB (Sect. 7.11.3) with each batch of samples.
Calculate accuracy as percent recovery using the following
equation:
LFB - LRB
X 100
where: R = percent recovery.
LFB = laboratory fortified blank.
LRB = laboratory reagent blank.
s = concentration equivalent of mercury
added to fortify the LRB solution.
If the recovery of mercury falls outside the required control
limits of 85-115%, the analysis is judged out of control, and
the source of the problem should be identified and resolved
before continuing analyses.
9.3.3 The laboratory must use LFB analyses data to assess laboratory
performance against the required control limits of 85-115%
(Sect.9.3.2). When sufficient internal performance data become
available (usually a minimum of twenty to thirty analyses),
optional control limits can be developed from the mean percent
recovery (x) and the standard deviation (S) of the mean percent
recovery. These data can be used to establish the upper and
lower control limits as follows:
UPPER CONTROL LIMIT = x + 3S
LOWER CONTROL LIMIT = x - 3S
The optional control limits must be equal to or better than the
required control limits of 85-115%. After each five to ten new
recovery measurements, new control limits can be calculated
using only the most recent twenty to thirty data points. Also,
the standard deviation (S) data should be used to establish an
on-going precision statement for the level of concentrations
included in the LFB. These data must be kept on file and be
available for review.
9.3.4 Instrument performance check (I PC) solution - For all
determinations the laboratory must analyze the IPC solution
(Sect. 7.12) and a calibration blank immediately following each
calibration, after every tenth sample (or more frequently, if
required) and at the end of the sample run. Analysis of the
calibration blank should always be < the MDL. Analysis of the
IPC solution immediately following calibration must verify that
the instrument is within ± 5% of calibration. Subsequent
245.1-11
Revision 3.0 May 1994
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analyses of the IPC solution must be within ± 10 % of
calibration. If the calibration cannot be verified within the
specified limits, analysis must be discontinued, the cause
determined and/or in the case of drift the instrument
recalibrated. All samples following the last acceptable IPC
solution must be reanalyzed. The analysis data of the
calibration blank and IPC solution must be kept on file with
the sample analyses data.
9.4 Assessing Analyte Recovery and Data Quality
9.4.1 Sample homogeneity and the chemical nature of the sample matrix
can affect mercury recovery and the quality of the data.
Taking separate aliquots from the sample for replicate and
fortified analyses can in some cases assess the effect. Unless
otherwise specified by the data user, laboratory or program,
the following laboratory fortified matrix (LFM) procedure (Sect
9.4.2) is required.
9.4.2 The laboratory must add a known amount of mercury to a minimum
of 10% of samples or one sample per sample set, whichever is
greater. In each case the LFM aliquot must be a duplicate of
the aliquot used for sample analysis. Select a sample with a
low mercury background that is representative of the type of
water samples being analyzed. It is recommended that this
sample be analyzed prior to fortification. The concentration
of mercury added may vary based on the nature of samples being
analyzed. When possible, the concentration should be the same
as that added to the LRB, but should not exceed the midpoint
concentration of the calibration curve. Over time, samples
from all routine sample sources should be fortified.
9.4.3 Calculate the percent recovery, corrected for background
concentration measured in the unfortified sample aliquot, and
compare these values to the control limits to the designated
LFM recovery range of 70-130%. Percent recovery may be
calculated using the following equation:
Cs - C
R = s x 100
where: R = percent recovery
Cs = fortified sample concentration
C = sample background concentration
s = concentration equivalent of mercury added to
water sample.
9.4.4 If mercury recovery falls outside the designated range, and the
laboratory performance is shown to be in control (Sect. 9.3),
245.1-12 Revision 3.0 May 1994
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the recovery problem encountered with the fortified water
sample is judged to be matrix related, not system related. The
result for mercury in the unfortified sample must be labelled
to inform the data user that the results are suspect due to
matrix effects.
10.0 CALIBRATION AND STANDARDIZATION
10.1 Conveniently arrange and connect the various components of the
instrument system using one of the options shown in Figure 1. If
adjustable, the monochromator should be set to 253.65 nm. Prior to
the use of this method the air flow should be optimized. (The
recommended air flow rate through the system is 1 liter per minute.)
For all determinations allow an instrument and hollow cathode lamp
warm up period of not less than 15 min. When an instrument designed
specifically for the determination of mercury by the cold vapor
technique is being utilized, the analyst should follow the
instructions provided by the manufacturer.
10.2 Before using the procedure (Section 11.0) to analyze samples, there
must be data available documenting initial demonstration of
performance. The required data and procedure is described in Section
9.2. This data must be generated using the same instrument operating
conditions and calibration routine used for sample analysis. These
documented data must be kept on file and be available for review by
the data user.
10.3 The recommended calibration routine is given in Section 11.2.
11.0 PROCEDURE
11.1 Sample Preparation
11.1.1 Transfer 100 ml of the water sample [or an aliquot diluted with
reagent water (Sect. 7.2) to 100 ml] into a sample container.
NOTE: For reduced volume analysis, adjust sample and reagent
volumes to maintain the required sample to reagent
ratios.
11.1.2 Add 5 ml of H2S04 (Sect. 7.4) and 2.5 ml of HN03 (Sect. 7.3) to
the container.
11.1.3 To each container add 15 ml KMn04 solution (Sect. 7.7). For
sewage or industry wastewaters, additional KMn04 may be
required. Shake and add additional portions of KMn04 solution,
if necessary, until the purple color persists for at least 15
min. Add 8 ml of K2S208 solution (Sect. 7.8) to each container.
Mix thoroughly, cap and cover the top of the sample container
(if required) with aluminum foil or other appropriate cover.
Heat for 2 h in a water bath at 95°C.
245.1-13 Revision 3.0 Hay 1994
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11.1.4 Remove the sample containers from the water bath and cool to
room temperature. (During the cool down period proceed with
instrument warm up and calibration.)
11.1.5 When the samples are at room temperature, to each container,
add 6 ml of NaCl-(NH2OH)2-H2S04 solution (Sect. 7.9) to reduce
the excess permanganate.
11.2 Sample Analysis
11.2.1 Before beginning daily calibration the instrument should be
reconfigured to the optimized conditions. Turn on the
instrument and circulating pump. Adjust pump rate to 1 L/min
or as required. Allow system to stabilize.
11.2.2 Prepare calibration standards by transferring 0.5, 1.0, 2.0,
5.0 and 10 ml aliquots of the 0.1 /zg/mL CAL (Sect. 7.6) to a
series of sample containers (Sect. 6.5.2). Dilute the standard
aliquots to 100 ml with reagent water (Sect. 7.2) and process
as described in Sects. 11.1.2, 11.1.3 (without heating), and
11.1.5. These solutions contain 0.05 to 1.0 ng of Hg. (Other
appropriate calibration standards, volumes, and ranges may also
be used.)
11.2.3 Treating each standard solution container individually, add 5
ml of SnCl2 solution (Sect. 7.10) and immediately attach the
container to the aeration apparatus. The absorbance, as
exhibited either on the instrument or recording device, will
increase and reach maximum within 30 sec. As soon as the
maximum response is obtained, approximately 1 min, open the
bypass value (or optionally remove aspirator from the sample
container if it is vented under the hood) and continue aeration
until the absorbance returns to its minimum value.
11.2.4 Close the by-pass value, remove the aspirator from the standard
solution container and continue aeration. Repeat (Sect.
11.2.3) until data from all standards have been collected.
11.2.5 Construct a standard curve by plotting peak height, area or
maximum response obtained from each standard solution, versus
micrograms of mercury in the container. The standard curve
must comply with Sect. 9.2.2. Calibration using computer or
calculator based regression curve fitting techniques on
concentration/response data is acceptable.
11.2.6 Following calibration the digested samples are analyzed in the
same manner as the standard solutions described in Section
11.2.3. However, prior to the addition of the SnCl, solution,
place the aspirator inside the container above the liquid, and
purge the head space (20 to 30 sec) to remove possible gaseous
interference.
245.1-14 Revision 3.0 May 1994
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11.2.7 During the analysis of samples, the laboratory must comply with
the required quality control described in Sections 9.3 and 9.4.
12.0 DATA ANALYSIS AND CALCULATIONS
12.1 From the prepared calibration curve (Sect. 11.2.4) compute sample
values by comparing response with the standard curve.
12.2 Calculate the mercury concentration in the sample by the formula:
in 1.000'
Pfcr/r - V& 9 n \ . \
Hg/L - \ aliquot ) (^ of aliquot)
12.3 Report mercury concentrations to the proper significant figures in
mg/L, /jg/L or ng/L as required.
13.0 METHOD PERFORMANCE
13.1 In a single laboratory (EMSL), using an Ohio River composite sample
with a background mercury concentration of 0.35 /Kj/L Hg and fortified
with concentration of 1.0, 3.0, and 4.0 /zg/L Hg, the standard
deviations were ± 0.14, ± 0.10 and + 0.08 /jg/L Hg, respectively.
Standard deviation at the 0.35 /zg/L Hg level was ± 0.16 ng/L Hg.
Percent recoveries at the three levels were 89%, 87%, and 87%,
respectively.
13.2 In a joint EPA/ASTM inter!aboratory study of the cold vapor technique
for total mercury in water, increments of organic and inorganic
mercury were added to natural waters. Recoveries were determined by
difference. A statistical summary of this study is found in Table 1.
14.0 POLLUTION PREVENTION
14.1 Pollution prevention encompasses any technique that reduces or
eliminates the quantity or toxicity of waste at the point of
generation. Numerous opportunities for pollution prevention exist in
laboratory operation. The EPA has established a preferred hierarchy
of environmental management techniques that places pollution
prevention as the management option of first choice. Whenever
feasible, laboratory personnel should use pollution prevention
techniques to address their waste generation. When wastes cannot be
feasibly reduced at the source, the Agency recommends recycling as the
next best option.
14.2 For information about pollution prevention that may be applicable to
laboratories and research institutions, consult Less is Better:
Laboratory Chemical Management for Waste Reduction, available from the
American Chemical Society's Department of Government Relations and
Science Policy, 1155 16th Street N.W., Washington D.C. 20036,
(202)872-4477.
245.1-15 Revision 3.0 May 1994
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15.0 WASTE MANAGEMENT
15.1 The Environmental Protection Agency requires that laboratory waste
management practices be conducted consistent with all applicable rule
and regulations. The Agency urges laboratories to protect the air,
water, and land by minimizing and controlling all releases from hoods
and bench operations, complying with the letter and spirit of any
sewer discharge permits and regulations, and by complying with all
solid and hazardous waste regulations, particularly the hazardous
waste identification rules and land disposal restrictions. For
further information on waste management consult The Waste Management
Manual for Laboratory Personnel, available from the American Chemical
Society at the address listed in the Sect. 14.2.
16.0 REFERENCES
1. Kopp, J.F., Longbottom, M.C., and Lobring, L.B., " 'Cold Vapor'
Method for Determining Mercury"; J. Am. Water Works Assoc.. Vol. 64,
No. 1, January 1972.
2. "Safety in Academic Chemistry Laboratories", American Chemical
Society Publication, Committee on Chemical Safety, 3rd Edition,
1979.
3. "OSHA Safety and Health Standards, General Industry", (29CFR 1910),
Occupational Safety and Health Administration, OSHA 2206, revised
January 1976.
4. "Proposed OSHA Safety and Health Standards, Laboratories",
Occupational Safety and Health Administration, Federal Register
July 24, 1986.
5. "Specification for Reagent Water", D1193, Annual Book of ASTM
Standards. Vol. 11.01, 1990. ""
6. Code of Federal Regulations 40, Ch. 1, Pt. 136 Appendix B.
245.1-16 Revision 3.0 May 1994
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17.0 TABLES. DIAGRAMS. FLOWCHARTS. AND VALIDATION DATA
TABLE 1. INTERLABORATORY PRECISION AND ACCURACY DATA
FOR FLAMELESS ATOMIC ABSORPTION
Number
of Labs
76
80
82
77
82
79
79
78
True Values
fld/L
0.21
0.27
0.51
0.60
3.4
4.1
8.8
9.6
Mean Value
uq/L
0.349
0.414
0.674
0.709
3.41
3.81
8.77
9.10
Standard
Deviation
«q/L
0.276
0.279
0.541
0.390
1.49
1.12
3.69
3.57
RSD
%
89
67
80
55
44
29
42
39
Mean
Accuracy as
% Bias
66
53
32
18
0.34
-7.1
-0.4
-5.2
245.1-17
Revision 3.0 May 1994
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i—O
Sample Solution
In B.O.D. Botda
Scrubber Containing a
Mercury Absorbing Medial
Option I
Sample Solution
In B.O.D. Bottia
Scrubber Containing a
Mercury Absorbing Media1!
Option
-<=3
Air Pump Drying Table
Carbon Trays
Absorption Cell
Bubbler
Sample Solution
In B.ODL Bottle
Options
Figure 1. Apparatus for Flameless Mercury Determination
Because of the toxic nature of mercury vapor, inhalation must be avoided.
Therefore, a bypass has been included in the system to either vent the mercury
vapor into an exhaust hood or pass the vapor through some absorbing media, such
as: a) equal volumes of 0.1 N KMnO4 and 10% H2SO4
b) 0.25% iodine in a 3% Kl solution.
A specially treated charcoal that will absorb mercury vapor is also available from
Barnebey and Cheney, P.O. Box 2526, Columbus, OH 43216, Catalog No. 580-13
or 580-22.
245.1-18
Revision 3.0 May 1994
•U.S. GOVERNMENT PRINTING OFFICE: 1994-550-001/00159
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