vvEPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/600/4-91/010
June 1991
Methods for the
Determination of
Metals in Environmental
Samples
Cr(VI)
10|ig/L
ICP-AES ICP-MS GF-AA 1C
COLD VAPOR HPLC-ECD GC-ECD
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EPA-600/4-91-010
June 1991
METHODS FOR THE DETERMINATION
OF METALS
IN ENVIRONMENTAL SAMPLES
ENVIRONMENTAL 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.
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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 EMSL-Cincinnati publication, "Methods for the Determination of
Metals in Environmental Samples" was prepared to gather together under a
single cover a set of 13 laboratory analytical methods for metals in a variety
of sample types. We are pleased to provide this 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
Thirteen analytical methods covering 35 analytes which may be present in
a variety of environmental sample types are described in detail. Three of
these methods are sample preparation procedures that require a separate
determinate step found in other methods in this manual or elsewhere. These
methods involve a wide range of analytical instrumentation including
inductively coupled plasma (ICP)/atomic emission spectroscopy (AES), ICP/mass
spectroscopy (MS), atomic absorption (AA) spectroscopy, ion chromatography
(1C), and high performance liquid chromatography (HPLC). Application of these
techniques to a diverse group of sample types is a somewhat unique feature of
this manual. Sample types include waters ranging from drinking water to
marine water as well as industrial and municipal wastewater, groundwater and
landfill leachate. Also included are methods that will accommodate biological
tissues, sediments, and soils.
IV
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TABLE OF CONTENTS
Method
Number
200.1
200.2
Title Revision Date
Disclaimer
Foreword
Abstract
Analyte - Method Cross Reference
Acknowledgement. . . .
Introduction and General Comments ....
Determination of Acid Soluble 2.0 4/91
Metals
Sample Preparation Procedure for 2.3 4/91
Page
1
3
13
Spectrochemical Determination of
Total Recoverable Elements
200.3 Sample Preparation Procedure for 1.0
Spectrochemical Determination of Total
Recoverable Elements in Biological
Tissues
200.7 Determination of Metals and Trace 3.3
Elements in Water and Wastes by
Inductively Coupled Plasma-Atomic
Emission Spectrometry
200.8 Determination of Trace Elements in 4.4
Water and Wastes by Inductively
Coupled Plasma - Mass Spectrometry
200.9 Determination of Trace Elements by 1.2
Stabilized Temperature Graphite Furnace
Atomic Absorption Spectrometry
200.10 Determination of Trace Elements in 1.4
Marine Waters by On-Line Chelation
Preconcentration and Inductively
Coupled Plasma - Mass Spectrometry
200.11 Determination of Metals in Fish 2.1
Tissue by Inductively Coupled Plasma-
Atomic Emission Spectrometry
4/91
4/91
4/91
4/91
4/91
4/91
23
31
83
123
153
177
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218.6 Determination of Dissolved Hexavalent 3.2 4/91 211
Chromium in Drinking Water,
Groundwater, and Industrial Wastewater
Effluents by Ion Chromatography
245.1 Determination of Mercury in Water by 2.3 4/91 227
Cold Vapor Atomic Absorption
Spectrometry
245.3 Determination of Inorganic Mercury 1.1 4/91 241
(II) and Selected Organomercurials
in Drinking and Ground Water by High
Performance Liquid Chromatography
(HPLC) with Electrochemical Detection
(ECD)
245.5 Determination of Mercury in Sediment 2.3 4/91 267
by Cold Vapor Atomic Absorption
Spectrometry
245.6 Determination of Mercury in Tissues 2.3 4/91 281
by Cold Vapor Atomic Absorption
Spectrometry
VI
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ACKNOWLEDGEMENT
This methods manual was prepared and assembled by the Inorganic Chemistry
Branch of the Chemistry Research Division, Environmental-Monitoring Systems
Laboratory - Cincinnati. John Creed, Otis Evans, Larry Lobring, Theodore
Martin and Billy Potter were major contributors to this effort. Special
thanks and appreciation are due to Diane Schirmann, Patricia Hurr and Helen
Brock for providing outstanding secretarial and word processing support and
for format improvements in presentation of the manual. James O'Dell is also
recognized for his contributions in both methods development and design of
this manual's cover.
In addition, Elizabeth Arar and Stephen Long, Technology Applications,
Inc., and William McDaniels, USEPA Region 4, are recognized for their
significant contributions. Finally, all method authors and contributors wish
to thank William Budde, Director of the Chemistry Research Division, and
Thomas Clark, Director of the Environmental Monitoring Systems Laboratory -
Cincinnati, for their cooperation and support during this project.
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INTRODUCTION
An integral component of the role of the Environmental Protection Agency
(EPA) in assessing and protecting the quality of the environment is the
provision of means for monitoring environmental quality. In keeping with this
role, EPA develops and disseminates analytical methods for measuring chemical
and physical parameters affecting this most important resource, including
contaminants which may have potential adverse effects upon the health of our
environment. This manual provides 13 analytical methods for 35 analytes which
may be present in a variety of environmental sample types. Three of the
methods are sample preparation procedures that refer to instrumental
techniques in other methods for multi-analyte or single-analyte quantitation.
The remaining 11 analytical methods were written to stand-alone, that is, each
method may be removed from the manual, photocopied, inserted into another
binder, and used without loss of information. Revisions of these methods will
be made available in a similar stand-alone format to facilitate the
replacement of existing methods as new technical developments occur. This
flexibility comes at the cost of some duplication of material, for example,
the definitions of terms section of each method is nearly identical. The
authors believe that the added bulk of the manual is a small price to pay for
the format flexibility.
An important feature of the methods in this manual is the consistent use
of terminology, and this feature is especially helpful in the quality control
sections where standardized terminology is not yet available. The terms were
carefully selected to be meaningful without extensive definition, and
therefore should be easy to understand and use. The names of authors of the
methods are provided to assist users in obtaining direct telephone support
when required.
GENERAL COMMENTS
The methods in this manual are not intended to be specific for any single
EPA regulation, compliance monitoring program, or specific study. In the
past, manuals have been developed and published that respond to specific
regulations, such as the Safe Drinking Water Act (SDWA) or to special studies
such as the Environmental Monitoring and Assessment Program (EMAP) Near
Coastal Demonstration Project. These methods are, however, available for
incorporation into several regulatory programs due to their applicability to
such diverse sample types. The ICP/AES, ICP/MS and AA methods have been or
will be approved for use in the drinking water and the permit programs. The
methods applicable for use in marine and estuary waters will be available for
use in the Agency's National Estuary Program and subsequent EMAP studies that
may involve the determination of toxic metals in the water column.
The quality assurance sections are uniform and contain minimum
requirements for operating a reliable monitoring program: initial
demonstration of performance, routine analyses of reagent blanks, analyses of
fortified reagent blanks and fortified matrix samples, and analyses of quality
control (QC) samples. Other QC practices are recommended and may be adopted
to meet the particular needs of monitoring programs e.g., analyses of field
reagent blanks, instrument control samples and performance evaluation samples.
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METHOD 200.1
DETERMINATION OF ACID-SOLUBLE METALS
Theodore D. Martin and James W. O'Dell
Inorganic Chemistry Branch
Chemistry Research Division
and
Gerald D. McKee
Office of the Director
Revision 2.0
April 1991
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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METHOD 200.1
DETERMINATION OF ACID-SOLUBLE METALS
1. SCOPE AND APPLICATION
1.1 This method can be used to determine acid-soluble metals1 in ambient
waters and aqueous wastes. Results from this method may be used to
calculate or estimate the potential impact on aquatic life and water
quality. It is applicable to the analysis of arsenic (As), cadmium
(Cd), chromium (Cr), copper (Cu), and lead (Pb).
1.2 This method provides instructions for sample handling, preservation,
and preparation prior to analysis using spectrochemical methods
given in this manual. Specific references are listed in Sect. 11.3
of this method.
1.3 This method is designed to be a supplement to approved EPA
spectrophotometric and spectrochemical methods, however, it does not
provide for oxidation state or organometallic speciation. For a
summary and description of the analytical techniques employed, their
estimated instrumental detection limits, definition of terms
specific to each technique, types of interferences encountered,
instrumental requirements, reagents and standards required for
analysis, calibration, general instrumental operating procedures,
instrumental quality control, data calculation and reporting, see
appropriate parts of the methods referenced in Sect. 11.3 of this
method.
2. SUMMARY OF METHOD
2.1 This method describes procedural instruction for treating an
aqueous sample for determination of acid-soluble metals prior to
either atomic absorption or atomic emission spectrochemical
analysis. The aqueous sample is acidified to a pH of 1..75 ±0.1 and
held for a period of at least 16 h before being filtered through a
0.45-#m membrane filter and appropriately processed for analysis.
3. DEFINITIONS
3.1 Acid-Soluble Metal: That portion of the metal concentration that
will pass through a 0.45-jum membrane filter after the solution to
be filtered has been adjusted to within a pH 1.75 ±0.1 and held for
a period of 16 h.
4. INTERFERENCES
4.1 Contamination is of primary concern in determining acid-soluble
metals. All sample containers, labware, filtering and sample
processing apparatus should be washed as described in Sect. 8.1.
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5. SAFETY
5.1 Ammonium hydroxide and nitric acid are moderately toxic and
irritating to skin and mucus membranes. Use concentrated reagents
in a hood 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. APPARATUS
6.1 pH Meter-laboratory or field model: A wide variety of instruments
are commercially available with various specifications and optional
equipment. The instrument must be capable of measuring pH to 0.1
units and should be a meter equipped with a combination electrode.
6.2 Filter funnel and support: Only glass or plastic filtering
apparatus should be used. The support should be capable of
accepting both the prefilter and fine filter while maintaining a
no-leak seal between the funnel and support. The Gelman model 4201
or equivalent is acceptable.
6.3 Suction flask, 500-mL capacity.
6.4 Membrane filter discs: Because the sample solution to be filtered
will be of low pH (1.75 ±0.1), the filter media may be either a
polyvinyl chloride acrylic copolymer or mixed esters of cellulose
material. The following 47-mm membrane filters or equivalent are
acceptable.
6.4.1 Fine prefilter: DM-800, 0.8-jum (Gelman No.64502)
6.4.2 Fine filter: DM-450, 0.45-/Jtn (Gelman No. 64515) or
HAWP-047, 0.45 /im (Millipore No. HAWP 047 00)
6.5 Sample collection containers: Cubitainer, polyethylene, 1 quart
(0.95L) capacity or equivalent.
6.6 Sample storage bottles: Wide-mouth high-density polyethylene with
polypropylene screw cap closure, 500-mL capacity.
6.7 Glassware: Class A volumetric flasks and pipets of various volumes.
6.8 For the apparatus and equipment needed for the analytical technique
employed, see the specific references.
7. REAGENTS AND STANDARDS
7.1 Deionized, distilled water: Prepare by passing distilled water
through a mixed bed of cation and anion exchange resins. Use
deionized, distilled water for the preparation of all reagents and
as dilution or rinse water. The purity of this water must be
equivalent to ASTM Type II reagent water of Specification D 1193 .
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7.2 Nitric acid, cone, (sp.gr. 1.41), ultra-high purity grade or
equivalent. Redistilled acid is acceptable.
7.2.1 Nitric acid, (1+1): Add 500 mL cone. HNO, (Sect. 7.2) to
400 mL deionized, distilled water (Sect. 7.1) and dilute to
•L L. •
7.3 Hydrochloric acid, cone. (sp. gr. 1.19).
7.3.1 Hydrochloric acid, (1+1): Add 500 ml cone. HC1 (Sect. 7.3)
to 400 ml deionized, distilled water (Sect. 7.1) and dilute
to 1 L.
7.4 Ammonium Hydroxide, (1+9): Dilute 10 ml cone, ammonium hydroxide,
NH4OH (analytical reagent grade), to 100 ml with deionized,
distilled water (Sect. 7.1).
7.5 Buffer solutions: Two buffer solutions are required, one in the
range of pH 2 and the other at pH 7. These may be prepared or
purchased as commercially available certified solutions. The use
of purchased buffer solutions certified at a pH of 2 and 7 is
recommended.
8. SAMPLE COLLECTION. PRESERVATION AND STORAGE
8.1 For the determination of acid-soluble metals, contamination and
loss are of prime concern. Dust in the laboratory environment,
impurities in reagents and improperly cleaned laboratory apparatus
which the sample contacts are all potential sources of
contamination. Sample containers can introduce either positive or
negative errors in the measurement of metals by (a) contributing
contaminants through leaching or surface desorption and/or (b) by
depleting concentration through adsorption. Laboratory glassware,
including the sample collection cubitainer and the polyethylene
sample storage bottle, as well as the filtering apparatus should be
thoroughly washed with detergent and tap water; thoroughly rinsed
with (1+1) nitric acid, tap water, (1+1) hydrochloric acid, tap
water and finally deionized distilled water in that order (See
Notes 1 and 2).
NOTE 1: To remove difficult organic deposits from glassware, a
commercial product, NOCHROMIX, available from Godax Laboratories,
480 Canal Street, New York, New York 10013 may be used. This
product should not be used on plastic containers or filtering
apparatus.
NOTE 2: If it can be documented through an active analytical
quality control program using spiked samples, laboratory control
standards and reagent blanks that certain steps in the cleaning
procedure are not required, those steps may be eliminated from the
procedure.
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8.2 At the time of sample collection, the sample cubitainer is rinsed
with the sample solution and the rinse portion discarded. The
cubitainer is then filled with approximately 800 ml of sample,
acidified with 2 ml of (1+1) nitric acid and mixed. For most
ambient waters the acid addition will lower the pH to near 2, but
not lower than 1.75. The cubitainer is sealed, placed in an ice
chest at 4°C, and returned to the laboratory. Note the date and
time of preservation on the sample tag.
8.3 The sample should not be held more than 3 days at 4°C from the day
of collection before processing is started. The filtrate is
estimated to be stable for 30 days.
9. CALIBRATION AND STANDARDIZATION
9.1
9.2
Calibration of pH meter - Because of the wide variety of pH meters
and accessories, detailed operating procedures cannot be
incorporated into this method. Each analyst must be acquainted
with the operation of the system being used and familiar with all
instrument functions. Special attention to care of the combination
electrode is recommended. See Method 150.1 given in EPA
600/4-79-020, March 19832.
Each instrument/electrode system must be calibrated at a
minimum of two points, one at or near pH 2, the other at pH 7.
Calibrate according to manufacturer's instructions and measure the
pH of each sample. Using deionized distilled water (Sect. 7.1),
rinse the electrode system after each pH measurement.
10. QUALITY CONTROL
10.1 The following quality assurance procedures represent 5% of the
analyzed sample load for 20 samples.
10.2 To measure recovery and cross contamination between samples that
may occur, 300 ml of a laboratory control standard containing all
six metals, each at a concentration above 10X its determined method
detection limit (MDL), is transferred to a cleaned cubitainer,
adjusted to a pH range of 1.75 ± 0.1 and allowed to stand for a
minimum of 16 h. At a selected point midway through the group of
samples to be analyzed, the control standard is filtered. The
analyzed values should be within the warning limits of ±2 standard
deviations of an established mean value as determined from seven
prior replicate analyses. If an analyzed value was greater than ±3
standard deviations from the mean, the analysis was out of control.
10.3 To determine the MDL of each metal, prepare seven aliquots of the
sample matrix of concern, spike the aliquots with each metal to a
concentration of 3 to 5 times its estimated detection limit and
follow the procedure - "Definition and Procedure for the
Determination of the Method Detection Limit.
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11. PROCEDURE
11.1 SAMPLE pH ADJUSTMENT - For the determination of acid-soluble
metals, the pH of the sample must be 1.75 ± 0.1. Upon receiving the
sample in the laboratory, check the sample tag for proper
preservation and to see that the holding time has not been
exceeded. Allow the sample to come to room temperature, calibrate
the pH meter and measure the pH of the sample in the cubitainer.
Using deionized distilled water (Sect. 7.1), rinse the electrode
system after each pH measurement. Do not wipe the electrode.
11.1.1 If the sample pH is between 1.65 and 1.85, mix the sample
and allow to stand at room temperature for a minimum of
16 h for required dissolution. At the end of the extraction
period, measure the pH again to verify that the proper pH
was maintained, and if so, filter according to paragraph
11.2. If pH was not maintained, a new sample should be
requested and more care and time taken in the initial pH
adjustment.
11.1.2 If the sample pH is above 1.85, add (1+1) nitric acid in a
dropwise manner, mix the sample in the cubitainer by
inverting and shaking and redetermine the pH. Continue
adding small increments of the (1+1) nitric acid and mix
until the sample is within the desired pH range. If the
pH should go below 1.65, add (1+9) ammonium hydroxide
(Sect. 7.3) in a dropwise manner until the sample is within
the pHrange of 1.65 to 1.85. Once the pH of the sample is
properly adjusted and thoroughly mixed, set the sample
aside for a minimum of 16 h for the required
dissolution to occur. At the end of the extraction
period, measure the pH again to verify the proper pH was
maintained, and if so, filter according to paragraph 11.2.
If pH was not maintained, a new sample should be
requested and more care and time taken in the initial pH
adjustment.
11.1.3 If upon receipt the sample has a pH below 1.65, the
sample should be discarded and the collection of a new
sample requested. The sample collection team should be
informed of the reason why the previous sample was
rejected.
11.2 SAMPLE FILTRATION - For determination of acid-soluble metals,
the pH-adjusted sample is filtered through a 0.45-jum membrane
filter. To prevent clogging of the filter, the sample is first
passed through a fine prefilter.
11.2.1 Before filtering any sample make certain that the
filtering apparatus (Sects. 6.2 and 6.3), polyethylene
storage bottles (Sect. 6.7) and other necessary glassware
have been cleaned by the procedure described in Sect. 8.1.
8
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11.2.2 Insert the filter support of the filtering apparatus through
the proper size rubber stopper and wrap the stopper with
1 in. PTFE laboratory tape to prevent contamination. Secure
the flask in an upright position and place the support in
the neck of the suction flask. Connect the suction flask to
the vacuum line.
11.2.3 Place the membrane filters (Sect. 6.4) on the filter support
in the following order: first the 0.45-/zm fine filter and
then the 0.8-pi prefilter. Assemble the filter funnel to
the support as recommended by the manufacturer.
11.2.4 Do not mix the sample, but carefully decant approximately
50 ml of sample from the cubitainer into the filtering
funnel and apply the vacuum. After filtration, break the
vacuum, remove the filtering apparatus, rinse the suction
flask with the filtrate and discard.
11.2.5 Reassemble the filtering apparatus and suction flask,
reapply the vacuum and carefully decant approximately 250 ml
of additional sample into the filtering apparatus.
11.2.6 When filtration is complete, break the vacuum, transfer
the filtrate to a labeled, cleaned, polyethylene storage
bottle (Sect. 6.7) and store until all analyses have been
completed, not to exceed 30 days. The remaining unfiltered
portion of the sample may be discarded.
11.2.7 Before filtering additional samples, discard the filters,
rinse the suction flask and filtering apparatus with copious
amounts of deionized distilled water (Sect. 7.1), discard
the rinse water and drain away any excess water.
11.2.8 Repeat the above procedure until all samples and quality
control aliquots have been filtered.
11.3 SAMPLE ANALYSES - The level of metal concentration will determine
the analytical method selected to complete the analysis.
11.3.1 Inductively coupled plasma-atomic emission (ICP)
spectrometric analyses - The acid-soluble metals As, Cd, Cr,
Cu and Pb can be analyzed by direct aspiration ICP
spectrometry using the procedure described in Method 200.7
of this manual. To prepare the sample for analyses, pipet
2 mL (1+1) hydrochloric acid into a 50-mL volumetric flask
and dilute to the mark with sample filtrate. This dilution
requires an appropriate factor be applied to the final
calculations. In the absence of an established MDL
(Sect. 10.2.1), the following estimated instrumental
detection limit for each element should be considered the
limit of analysis.
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Estimated Detection Limit
Element mg/L
As 0.03
Cd 0.02
Cr 0.007
Cu 0.003
Pb 0.03
11.3.2 Direct aspiration flame atomic absorption (FLAA) analyses
- The acid-soluble metals Cd, Cr, Cu and Pb can be
analyzed by procedures given in approved FLAA methods
without requiring additional processing of the filtrate
before analysis. Listed below are the method numbers and
estimated instrumental detection limits, which in the
absence of an established MDL (Sect. 10,2.1), should be
considered the FLAA limit of analysis for direct aspiration.
In addition to the individual methods, for the proper
analysis procedure, see parts 9.1 of Section 200.0:
Atomic Absorption Methods given in EPA 600/4-79-020,
March 19832 .
Method Estimated Detection
Element Number Limit. mq/L
Cd 213.1 0.005
Cr 218.1 0.05
Cu 220.1 0.02
Pb 239.1 0.1
11.3.3 Stabilized Temperature Graphite Furnace Atomic Absorption
(STGFAA) ANALYSES - For STGFAA analysis of the acid-soluble
metals As, Cd, Cr, Cu and Pb, an aliquot of the filtrate
must be treated with the appropriate matrix modifiers
before analysis. For proper instrumental STGFAA calibration
and suggested operating conditions see Method 200.9 of this
manual. In the absence of an established MDL
(Sect. 10.2.1), the following estimated STGFAA instrumental
detection limit for each element should be considered the
limit of anaysis.
Estimated Detection Limit
El ement ng/L
As 0.9
Cd 0.05
Cr 0.2
Cu 1.0
10
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12. CALCULATIONS
12.1 See the appropriate section of the recommended methods of analysis.
12.2 Final results of these calculations should be reported as mg/L acid-
soluble metal.
13. PRECISION AND RECOVERY
13.1 Precision and recovery data for Cd, Cr, Cu, and Pb by this method
using inductively coupled plasma-atomic emission spectrometric
analyses are given in Table 1. The data are for three levels of
concentration using varying amounts of the same sludge material
spiked into river water. Seven replicate samples were prepared for
each level of concentration. River water controls were subtracted
from each level of spike. The percent recovery calculation is based
on "total-recoverable" analysis of the same samples. Accuracy data
on actual samples cannot be obtained.
13.2 Precision data on the determination of acid-soluble metals by this
method using atomic absorption spectrophotometric analyses are
estimated to be similar to the data in the methods referenced.
14. REFERENCES
1. Water Quality Criteria; Availability of Documents, Federal Register,
Vol. 50, No. 145, July 29, 1985, pp. 30784-30796.
2. Chemical Analysis of Water and Wastes, EPA 600/4-79-020, (Revised,
March 1983), U.S. Environmental Protection Agency, Office of
Research and Development, Environmental Monitoring and Support
Laboratory, Cincinnati, Ohio.
3. Annual Book of ASTM Standards, Part 31, American Society for Testing
and Materials, 1916 Race St., Philadelphia, PA, 19103.
4. Code of Federal Regulations 40, Ch. 1, Pt. 136 Appendix B.
11
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-------
METHOD 200.2
SAMPLE PREPARATION PROCEDURE FOR SPECTROCHEMICAL
DETERMINATION OF TOTAL RECOVERABLE ELEMENTS
Theodore D. Martin, John T. Creed
Inorganic Chemistry Branch
Chemistry Research Division
and
Stephen E. Long
Technology Applications, Inc.
Revision 2.3
April 1991
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
13
-------
METHOD 200.2
SAMPLE PREPARATION PROCEDURE FOR SPECTROCHEMICAL DETERMINATION
OF TOTAL RECOVERABLE ELEMENTS
1. SCOPE AND APPLICATION
1.1 This method provides sample preparation procedures for the
determination of total recoverable elements in groundwaters, surface
waters, drinking waters, wastewaters, and, with the exception of
silica, sediments, sludges and solid waste samples.
1.2 This method is applicable to the following analytes:
Analyte
Aluminum
Antimony
Arsenic
Boron
Barium
Beryl 1i urn
Cadmium
Calcium
Chromi urn
Cobalt
Copper
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Phosphorus
Potassium
Selenium
Silica
Silver
Sodium
Strontium
Thallium
Thorium
Tin
Uranium
Vanadium
Zinc
Chemical Abstract Services
Registry Numbers (CASRW
(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)
(Tl)
(Th)
(Sn)
(U)
(V)
(Zn)
7429-
7440-
7440-
7440-
7440-
7440-
7440-
7440-
7440-
7440-
7440-
7439-
7439-
7439-
7439-
7439-
7439-
7439-
7440
7723
7440
7782
7631
7440
7440
7440
7440
7440
7440
7440
7440
7440
90-5
36-0
38-2
•42-8
•39-3
•41-7
•43-9
-70-2
•47-3
•48-4
-50-8
-89-6
-92-1
-93-2
-95-4
-96-5
-97-6
-98-7
-02-0
-14-0
-09-7
-49-2
-86-9
-22-4
-23-5
-24-6
-28-0
-29-1
-31-5
-61-1
-62-2
-66-6
14
-------
1.3 Samples prepared by this method can be analyzed by the following
methods given in this manual: 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, the direct aspiration
flame atomic absorption methods given in "Methods for Chemical
Analysis of Water and Wastes", EPA 600/4-79-020, March 1983 can be
used for analysis. See the analytical methodology mentioned for
selection of the appropriate method for the determination of a
specific analyte.
1.4
1.5
1.6
1.7
This method is applicable to the preparation of drinking water
samples for the determination of metal and metalloid contaminants.
However, it can only be used prior to an approved analytical method
for compliance monitoring when included in the approved method or
when listed as a separately approved method in the Federal Register.
It should be noted that some primary drinking water metal
contaminants require that a 4X preconcentration be used prior to
analysis instead of the 2X preconcentration described in this
method.
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.
When using this method for determination of boron and silica in
aqueous samples,~only plastic or quartz labware should be used from
the time of sample collection to the completion of the analysis.
For accurate determinations of boron in solid sample extracts at
concentrations below 100 mg/Kg, only quartz beakers should be used
in the digestion with the immediate transfer of an extract aliquot
to a plastic centrifuge tube following dilution of the digestate to
volume. For these determinations, borosilicate glass must not be
used in order to avoid sample contamination of these analytes from
the glass.
This method will solubilize and hold in solution only minimal
concentrations of barium, as barium sulfate. In addition, the
stability of solubilized barium is greatly affected when free
sulfate is available in solution. The concentration of barium that
will remain in solution decreases as the free sulfate concentration
increases. [For example, when a 100 ml aliquot of drinking water
containing 60 mg/L sulfate was fortified with 5 mg of BaSO, salt
(equivalent to 59 mg/L Ba in the 2X analysis solution) only 33 mg/L
Ba was initially solubilized using the procedure given in Sect.
11.2. Upon standing one week, the barium concentration decreased to
12 mg/L. When 100 mL of deionized distilled water was fortified, the
entire 5 mg of BaS04 was solubilized and remained in solution over
15
-------
the same time period.] For more accurate determinations of barium
in samples having varying and unknown concentrations of sulfate,
samples should be analyzed as soon as possible after preparation is
completed.
2. SUMMARY OF METHOD
2.1 Solid and aqueous samples are prepared in a similar manner for
analysis. Metals and toxic elements are extracted from either solid
samples or the solid phase portion of aqueous samples by refluxing
the sample for 30 min in a mixture of nitric and hydrochloric acids.
After extraction, the solubilized analytes are diluted to specified
volumes with ASTM type I water. Diluted samples are to be analyzed
by mass and/or atomic spectrometry methods as soon as possible after
preparation.
3. DEFINITIONS
3.1 TOTAL RECOVERABLE - 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.
4. 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 plastic
labware should be used. When quartz beakers are not available for
digestion of solid samples, to reduce boron contamination,
immediately transfer an aliquot of the diluted digestate 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. 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 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
16
-------
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.2'3'4
6. APPARATUS AND EQUIPMENT
6.1 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, Teflon, etc.), including the sample container, should
be cleaned prior to use. Labware should be soaked overnight and
thoroughly washed with laboratory-grade detergent and water, rinsed
with water, and soaked for four hours in a mixture of dilute nitric
and hydrochloric acid (1+2+9), followed by rinsing with water, ASTM
type I water and oven drying.
NOTE: Chromic acid must not be used for cleaning glassware.
6.1.1 Labware - Volumetric flasks, graduated cylinders, funnels and
centrifuge tubes (glass and/or metal free plastic).
6.1.2 Assorted calibrated pipettes.
6.1.3 Conical Phillips beakers, 250-mL with 50-mm watch glasses.
Griffin beakers, 250-mL with 75-mm watch glasses.
Teflon and/or quartz beakers, 250-mL with Teflon covers
(optional).
6.1.4 Wash bottle - One piece stem, Teflon FEP bottle with Tefzel
ETFE screw closure, 125-mL capacity.
6.2 SAMPLE PROCESSING EQUIPMENT
6.2.1 Hot plate: Ceramic top, graduated dial 90°C to 450°C
(Corning PC100 or equivalent).
6.2.2 Single pan balance: Balance capable of weighing to the
nearest 0.01 g.
6.2.3 Analytical balance: Balance capable of weighing to the
nearest 0.0001 g.
17
-------
6.2.4 Centrifuge: Steel cabinet with guard bowl, electric timer
and brake. (International Centrifuge, Universal Model UV or
equivalent.)
6.2.5 Drying oven: Gravity convection oven, with thermostatic
control capable of maintaining 180°C ±'5°C.
7. REAGENTS AND CONSUMABLE MATERIALS
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 grade.
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 1 L.
7.2 WATER - For all sample preparation and dilutions, ASTM type I water
(ASTM D1193)5 is required. Suitable water may be prepared by
passing distilled water through a mixed bed of anion and cation
exchange resins.
8. SAMPLE COLLECTION. PRESERVATION AND STORAGE
8.1 For determination of total recoverable elements in aqueous samples,
acidify with (1+1) nitric acid at the time of collection to pH <2
normally, 3 ml of (1+1) nitric acid per liter of sample is
sufficient for most ambient and drinking water samples). The sample
should not be filtered prior to analysis.
NOTE: Samples that cannot be acid preserved at the time of
collection because of sampling limitations or transport
restrictions, should be acidified with nitric acid to a pH <2 upon
receipt in the laboratory. Following acidification, the sample
should be held for 16 h before withdrawing an aliquot for sample
processing.
8.2 Solid samples usually require no preservation prior to analysis
other than storage at 4°C.
18
-------
9. CALIBRATION AND STANDARDIZATION
9.1 Not applicable. Follow instructions given in the analytical method
selected.
10. QUALITY CONTROL
10.1 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.
10.2 Specific instructions on accomplishing the described aspects of the
QC program are discussed in the analytical methods (Sect. 1.3).
11. PROCEDURE
11.1 Sample Preparation - Aqueous Samples
For determination of total recoverable elements in water or
wastewater, take a 100 mL (± 1 ml) aliquot from a well mixed, acid
preserved sample containing not more than 0.25% (w/v) total solids
and transfer to a 250-mL Griffin beaker. (If total solids are
greater than 0.25% reduce the size of the aliquot by a proportionate
amount.) Add 2 ml of (1+1) nitric acid and 1 ml of (1+1)
hydrochloric acid. Heat on a hot plate at 85°C until the volume has
been reduced to approximately 20 ml, ensuring that the sample does
not boil. (A spare beaker containing approximately 20 ml of water
can be used as a gauge).
NOTE: For proper heating adjust the temperature control of the
hot plate such that an uncovered beaker containing 50 ml of
water located in the center of the hot plate can be maintained
at a temperature no higher than 85°C. Evaporation time for
100 ml of sample at 85°C is approximately two hours with the
rate of evaporation rapidly increasing as the sample volume
approaches 20 ml.
Cover the beaker with a watch glass and reflux for 30 min. Slight
boiling may occur but vigorous boiling should be avoided. Allow to
cool and quantitatively transfer to either a 50-mL volumetric flask
or a'50-mL class A stoppered graduated cylinder. Dilute to volume
with ASTM type I water and mix. Centrifuge the sample or allow to
stand overnight to separate insoluble material. 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
(Sect. 1.3). For analyses by inductively coupled plasma-mass
19
-------
12.
spectrometry, pipette 20 ml of the prepared solution into a 50-mL
volumetric flask, dilute to volume with ASTM type I water and mix.
(Internal standards are added at the time of 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.
11.2 Sample Preparation - Solid Samples
For determination of total recoverable elements in solid samples
(sludge, soils, and sediments), mix the sample thoroughly to achieve
homogeneity and weigh accurately a 1.0 ± 0.01 g portion of the
sample. Transfer to a 250-mL Phillips beaker. Add 4 mL (1+1)
nitric acid and 10 ml (1+4) hydrochloric acid. Cover with a watch
glass. Heat the sample on a hot plate and gently reflux for 30 min.
Very slight boiling may occur, however vigorous boiling must be
avoided to prevent the loss of HC1-H20 azeotrope.
NOTE: For proper heating adjust the temperature control of the
hot plate such than an uncovered Griffin beaker containing 50 ml
of water located in the center of the hot plate can be
maintained at a temperature approximately but no higher than
85°C.
Allow the sample to cool and quantitatively transfer to a 100-mL
volumetric flask. Dilute to volume with ASTM type I water and mix.
Centrifuge the sample or allow to stand overnight to separate
insoluble material. 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 (Sect. 1.3). For analysis by inductively
coupled plasma-mass spectrometry, pipette 10 ml into a 50-mL
volumetric flask, dilute to volume with ASTM type I water and mix.
(Internal standards are added at the time of 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. To
determine the dry weight transfer a separate, uniform 1 gram
aliquot to an evaporating dish and dry to a constant weight at
103°-105°C.
11.3 Sample Analysis - Use an analytical method listed in Sect. 1.3.
CALCULATIONS
12.1 Not applicable. Discussed in analytical methods listed in
Sect. 1.3.
20
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13. PRECISION AND ACCURACY
13.1 Not applicable. Available data included in analytical methods
listed in Sect. 1.3.
14. 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.
21
-------
-------
METHOD 200.3
SAMPLE PREPARATION PROCEDURE FOR SPECTROCHEMICAL
DETERMINATION OF TOTAL RECOVERABLE ELEMENTS IN BIOLOGICAL TISSUES
William McDanlel
Environmental Services Division
Region IV
U. S. Environmental Protection Agency
Revision 1.0
April 1991
Adapted by:
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
23
-------
METHOD 200.3
SAMPLE PREPARATION PROCEDURE FOR SPECTROCHEMICAL DETERMINATION
OF TOTAL RECOVERABLE ELEMENTS IN BIOLOGICAL TISSUES
1. SCOPE AND APPLICATION
1.1 This method provides sample preparation procedures for the
determination of total recoverable elements in biological tissue
samples.
1.2 This method is applicable to the following elements:
Analyte
1.3
Aluminum
Antimony
Arsenic
Barium
Beryl 1i urn
Cadmi urn
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Phosphorus
Potassium
Selenium
Silver
Sodium
Strontium
Thallium
Thorium
Uranium
Vanadium
Zinc
(Al)
(Sb)
(As)
(Ba)
(Be)
(Cd)
(Ca)
(Cr)
(Co)
(Cu)
(Fe)
(Pb)
(Li)
(Mg)
(Mn)
(HG)
(Mo)
(Ni)
(P)
(K)
(Se)
(Ag)
(Na)
(Sr)
(Tl)
(Th)
(U)
(V)
(Zn)
Chemical Abstract Services
Registry Numbers
7429-
7440-
7440-
7440-
7440-
7440-
7440-
7440-
7440-
7440-
7439-
7439-
7439-
7439-
7439-
7439-
7439-
7440-
7723-
7440-
7782-
7440-
7440-
7440-
7440-
7440-
7440-
7440-
7440-
-90-5
-36-0
-38-2
-39-3
-41-7
-43-9
-70-2
-47-3
-48-4
•50-8
-89-6
•92-1
•93-2
•95-4
•96-5
•97-6
•98-7
•02-0
•14-0
09-7
49-2
22-4
23-5
24-6
28-0
29-1
61-1
62-2
66-6
Samples prepared by this method can be analyzed by inductively
coupled plasma-atomic emission spectrometry (ICP-AES) Method 200.7,
"Determination of Metals and Trace Elements by Inductively Coupled
Plasma-Atomic Emission Spectrometry," inductively coupled plasma-
mass spectrometry (ICP-MS) Method 200.8, "Determination of Metals
24
-------
and Trace Elements by Inductively Coupled Plasma-Mass Spectrometry,"
and stabilized temperature platform graphite furnace atomic
absorption (STGFAA), Method 200.9, "Determination of Trace Elements
by Stabilized Temperature Graphite Furnace Atomic Absorption
Spectrometry". See analytical methods mentioned for selection of
the appropriate method for determination of a specific analyte.
SUMMARY OF METHOD
2.1 Up to 5 g of a frozen tissue sample is transferred to a 125 mL
flask. The tissue is digested with nitric acid, hydrogen peroxide
and heat. This digestion results in a clear solution that is then
analyzed by mass or atomic Spectrometry methods. The determined
metal concentration is reported in microgram/gram (/jg/g) wet tissue
weight.
DEFINITIONS
3.1 TOTAL RECOVERABLE - 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.
3.2 LABORATORY REAGENT BLANK (LRB) - A solution of reagents that is
treated exactly as a sample including exposure to all glassware and
equipment 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.
INTERFERENCES
4.1 Chromium contamination of biological samples from the use of
stainless steel has been reported.4 Use of special cutting
implements and dissecting board made from materials that are not of
interest is recommended. Knife blades made of titanium with Teflon
handles have been successfully used.
4.2 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.
4.3 Chemical interferences are matrix dependent and cannot be predicted.
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 Material safety data sheets for all chemical reagents should be
available to and understood by all personnel using this method.
Concentrated nitric and hydrochloric acids are moderately toxic and
extremely irritating to skin and mucus membranes. Hydrogen peroxide
25
-------
is a strong oxidizing reagent. 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. APPARATUS AND EQUIPMENT
6.1 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 contributing contaminants through surface
desorption/leaching, or depleting element concentrations through
adsorption processes. All reusable labware (glass, quartz,
polyethylene, Teflon, etc.), including the sample container, should
be cleaned prior to use or shown to be contaminant free. Labware
should be soaked overnight and thoroughly washed with laboratory-
grade detergent and water, rinsed with water, and soaked for four
hours in a mixture of dilute nitric and hydrochloric acid (1+2+9),
followed by rinsing with water, ASTM type I water and oven drying.
NOTE: Chromic acid must not be used for cleaning glassware.
6.1.1 Glassware - Volumetric flasks, graduated cylinders and 125-mL
Erlenmeyer flasks.
6.1.2 Assorted calibrated pipettes.
6.1.3 Wash bottle - One piece stem, Teflon FEP bottle with Tefzel
ETFE screw closure, 125-mL capacity.
6.2 SAMPLE PROCESSING EQUIPMENT
6.2.1 Balance - Analytical, capable of accurately weighing to
0.1 mg.
6.2.2 Hot Plate - (Corning PC100 or equivalent). An oscillating
hot plate will aid in sample digestion.
6.3 TISSUE DISSECTING EQUIPMENT
6.3.1. Dissecting Board: Polyethylene or other inert, nonmetallic
material, any non-wetting, easy-to-clean or disposable
surface is suitable. Adhesive backed Teflon or plastic
film may be convenient to use.
6.3.2 Forceps: Plastic, Teflon or Teflon coated.
26
-------
6.3.3 Surgical Blades: Disposable stainless steel with stainless
steel or plastic handle (Sect. 4.1).
6.3.4 Scissors: Stainless steel.
6.3.5 Plastic bags with watertight seal, metal free.
6.3.6 Label tape: Self-adhesive, vinyl coated marking tape,
solvent resistant, usable for temperatures from +121°C
to -23°C.
6.3.7 Polyvinyl chloride or rubber gloves, talc-free.
7. REAGENTS AND CONSUMABLE MATERIALS
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 grade.
7.1.1 Nitric acid, concentrated (sp.gr. 1.41).
7.1.2 Hydrochloric acid, concentrated (sp.gr. 1.19).
7.1.3 Hydrogen peroxide (30%)
7.2 WATER - For all sample preparation and dilutions, ASTM type I water
(ASTM D1193) is required. Suitable water may be prepared by passing
distilled water through a mixed bed of anion and cation exchange
resins.
8. SAMPLE COLLECTION. PRESERVATION AND STORAGE
8.1 Appropriate individual tissue samples should be taken soon after
collection and must be taken prior to freezing . If dissection of
the tissue cannot be performed immediately after collection, it
should be placed in a plastic bag (Sect. 6.3.5), sealed and placed
on ice or refrigerated at approximately 4°C.
8.2 Prior to dissection, the tissue should be rinsed with metal-free
water and blotted dry. Dissection should be performed within
24 hours of collection. Each individual tissue sample should also
be rinsed with metal-free water, blotted dry, and frozen at <-20°C
(dry ice).
8.3 Tissue samples of up to 5 g should be taken using a special
implement (Sect. 4.1) and handled with plastic forceps
(Sect. 6.S.2)3'4.
8.4 A maximum holding time for frozen samples has not been determined.
27
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9. CALIBRATION AND STANDARDIZATION
9.1 Not applicable. Follow instructions given in the analytical method
selected.
10. QUALITY CONTROL
10.1 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 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 data generated.
10.2 Specific instructions on accomplishing the described aspects of the
QC program are discussed in the analytical methods.
11. PROCEDURE
11.1 Sample Preparation - Place up to a 5 g subsample of frozen tissue
into a 125-mL erlenmeyer flask. Any sample spiking solutions should
be added at this time and allowed to be in contact with the sample
prior to addition of acid.
11.2 Add 10 ml of concentrated nitric acid and warm on a hot plate until
the tissue is solubilized. Gentle swirling the samples or use of an
oscillating hot plate will aid in this process.
11.3 Increase temperature to near boiling until the solution begins to
turn brown. Cool sample, add an additional 5 ml of concentrated
nitric acid and return to the hot plate until the solution once
again begins to turn brown.
11.4 Cool sample, add an additional 2 ml of concentrated nitric acid,
return to the hot plate and reduce the volume to 5-10 mL. Cool
sample, add 2 mL of 30% hydrogen peroxide, return sample to the hot
plate and reduce the volume to 5-10 mL.
11.5 Repeat Sect. 11.4 until the solution is clear or until a total of
10 mL of peroxide has been added. NOTE: A laboratory reagent blank
is especially critical in this procedure because the procedure
concentrates any reagent contaminants.
11.6 Cool the sample, add 2 mL of concentrated hydrochloric acid, return
to the hot plate and reduce the volume to 5 mL.
11
.7 Allow the sample to cool and quantitatively transfer to a 100-mL
volumetric flask. Dilute to volume with ASTM type I water, mix, and
allow any insoluble material to separate. The sample is now ready
for analysis by either ICP-AES or STGFAA. For analysis by ICP-MS an
additional dilution (1+4) is required.
28
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11.8 Sample Analysis - Use one of the analytical methods listed in
Sect. 1.3.
12. CALCULATIONS
12.1 Not applicable. Discussed in analytical methods listed in Sect.
1.3.
13. PRECISION AND ACCURACY
13.1 Not applicable. Available data included in analytical methods
listed in Sect. 1.3.
14. REFERENCES
1. Versieck, J., and F. Barbier, "Sample Contamination as A Source of
Error in Trace-Element Analysis of Biological Samples," Talanta.
Vol. 29, pp. 973-984, 1982.
2. Ney, J. J., and M. G. Martin, "Influences of Prefreezing on Heavy
Metal Concentrations in Bluegill Sunfish," Water Res.. Vol. 19,
No. 7, pp. 905-907, 1985.
3. "The Pilot National Environmental Specimen Bank," NBS Special
Publication 656, U. S. Department of Commerce, August, 1983.
4. Koirtyohann, S. R., and H. C. Hopps, "Sample Selection, Collection,
Preservation and Storage for Data Bank on Trace Elements in Human
Tissue," Federation Proceedings, Vol. 40, No. 8, June, 1981.
29
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METHOD 200.7
DETERMINATION OF METALS AND TRACE ELEMENTS IN WATER
AND WASTES BY INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY
Theodore D. Martin, Carol A. Brockhoff and John T. Creed
Inorganic Chemistry Branch
Chemistry Research Division
and
Stephen E. Long
Technology Applications, Inc.
Revision 3.3
April 1991
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
31
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METHOD 200.7
DETERMINATION OF METALS AND TRACE ELEMENTS
BY INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY
1.2
1. SCOPE AND APPLICATION
1.1 This method provides procedures for determination of dissolved
elements in ground waters, surface waters, and drinking water
supplies. It may also be used for determination of total
recoverable element concentrations in these waters and wastewaters
and, with the exception of silica, in sediments, sludges and solid
waste samples.
Dissolved elements are determined after suitable filtration and acid
preservation. Acid digestion procedures are required prior to the
determination of total recoverable elements. To reduce potential
interferences, dissolved solids should be < 0.2% (w/v)
(Sect. 4.1.2). v ' ''
Estuarine water may be analyzed by this method, however, matrix
matched standards or the method of standard addition (Sect. 9.8)
must be used following sample preparation (Sect. 11.2.2). Prepared
samples may require dilution prior to analysis to avoid physical
interferences (Sect. 4.1.2) and problematic operation of the sample
introduction system.
1.4 This method is applicable to the following analytes:
1.3
Analvte
Aluminum
Antimony
Arsenic
Barium
Beryl 1i urn
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Chemical Abstract Services
Registry Numbers fCASRN)
(Al)
(Sb)
(As)
(Ba)
(Be)
(B)
(Cd)
(Ca)
(Cr)
(Co)
(Cu)
(Fe)
(Pb)
(Li)
(Mg)
(Mn)
(Hg)
(Mo)
(Ni)
7429-
7440-
7440-
7440-
7440-
7440-
7440-
7440-
7440-
7440-
7440-
7439-
7439-
7439-
7439-
7439-
7439-
7439-
7440-
-90-5
-36-0
-38-2
-39-3
-41-7
•42-8
•43-9
•70-2
•47-3
•48-4
50-8
89-6
92-1
93-1
95-4
96-5
97-6
98-7
02-0
32
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Phosphorus
Potassium
Selenium
Silica
Silver
Sodium
Strontium
Thallium
Tin
Vanadium
Zinc
(P)
(K)
(Se)
(Si02)
(Ag)
(Na)
(Sr)
(Tl)
(Sn)
(V)
(Zn)
7723-14-0
7440-09-7
7782-49-2
7631-86-9
7440-22-4
7440-23-5
7440-24-6
7440-28-0
7440-31-5
7440-62-2
7440-66-6
Listed in Table 1 are the recommended wavelengths for these analytes
along with adjacent locations for background correction. Also
listed in Table 1 are typical instrument detection limits (IDLs
Sect. 3.3) determined using reagent acid ASTM type I water and
conventional pneumatic nebulization sample introduction into the
plasma. These IDLs are intended as a guide and may vary for each
laboratory depending on instrumentation and selected operating
conditions. Wavelengths and background correction locations other
than those recommended may be substituted if they provide the needed
sensitivity and are properly corrected for interelement spectral
interferences.
1.5 Specific instrumental operating conditions are given in Table 4.
However, because of the differences between various makes and models
of spectrometers, the analyst should follow the instrument
manufacturer's instructions and if possible, approximate the
recommended conditions given (Table 4).
1.6 When using this method for determination of boron and silica in
aqueous samples, only plastic, Teflon or quartz labware should be
used from time of sample collection to completion of analysis. For
accurate determinations of boron in solid sample extracts at
concentrations below 100 mg/kg, only quartz beakers should be used
in the digestion with immediate transfer of an extract aliquot to a
plastic centrifuge tube following dilution of the digestate to
volume. For these determinations, borosilicate glass must not be
used in order to avoid sample contamination of these analytes from
the glass.
1.7 This method is applicable to analysis of drinking water for the
determination of primary and secondary contaminant metals. However,
it can only be used for compliance monitoring of a drinking water
contaminant when listed in the Federal Register as an approved
method and laboratory performance data meet the required method
detection limit (MDL) or practical quantification limit (PQL)
established by the Office of Ground Water and Drinking Water. All
drinking water samples must be pretreated with acid prior to
analysis. When pneumatic nebulization is used for these
determinations, certain analytes require 4X preconcentration prior
to analysis instead of the 2X preconcentration procedure given in
33
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Sect. 11.2.1 of this method. Analytes requiring 4X preconcentration
are noted in the Federal Register at the time the method is
promulgated.
1.8 This method is suitable for 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.
1.9 The sample preparation procedures given in Sects. 11.2 and 11.3 will
solubilize and hold in solution only minimal concentrations of
barium, as barium sulfate. In addition, the stability of
solubilized barium is greatly affected when free sulfate is
available in solution. The concentration of barium that will remain
in solution decreases as the free sulfate concentration increases.
[For example, when a 100 ml aliquot of drinking water containing
60 mg/L sulfate was fortified with 5 mg of BaS04 salt (equivalent to
59 mg/L Ba in the 2X analysis solution) only 33 mg/L Ba was
initially solubilized using the procedure given Sect. 11.2.1. Upon
standing one week, the barium concentration decreased to 12 mg/L.
When 100 mL of deionized distilled water was fortified, the entire
5 mg of BaSO, was solubilized and remained in solution over the same
time period.] For more accurate determinations of barium in samples
having varying and unknown concentrations of sulfate, samples should
be analyzed as soon as possible after sample preparation is
completed.
1.10 With the exception of estuarine waters, once the samples have been
collected, approximately 20 samples including the mandatory quality
control samples can be analyzed using this method during a 1.5 work
day period.
2. SUMMARY OF METHOD
2.1 This method describes a technique for simultaneous or sequential
multielement determination of metals and trace elements in solution.
The basis of the method is the measurement of atomic emission by an
optical spectrometric technique. Samples are nebulized and the
aerosol that is produced is transported to the plasma torch where
desolyation and excitation occur. Characteristic atomic-line
emission spectra are produced by a radio-frequency inductively
coupled plasma (ICP). The spectra are dispersed by a grating
spectrometer, and line intensities are monitored by a photosensitive
device (e.g. photomultiplier tube or diode array). 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 analyte
lines on samples during analysis. The position selected for the
background intensity measurement, on either or both sides of the
analytical line, will be determined by the complexity of the
34
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spectrum adjacent to the analyte line. The position used must
either be free of spectral interference or adequately corrected to
reflect the same change in background intensity as occurs at the
analyte wavelength measured. Background correction is not required
in cases of line broadening where a background correction
measurement would actually degrade the analytical result. The
possibility of additional interferences named in Sect. 4.1 (and
tests for their presence as described in Sect. 4.2) should also be
recognized and appropriate corrections made.
3. DEFINITIONS
3.1 DISSOLVED - The concentration of analyte that will pass through a
0.45-/im membrane filter assembly, prior to sample acidification.
3.2 TOTAL RECOVERABLE - The concentration of an analyte determined in an
unfiltered sample following treatment by refluxing with hot, dilute
mineral acid.
3.3 INSTRUMENTAL 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 a reagent
blank signal at the same wavelength.
3.4 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. 10.2.2).
3.5 LINEAR DYNAMIC RANGE (LDR) - The concentration range over which the
analytical curve remains linear (Sect. 10.2.3).
3.6 METHOD OF STANDARD ADDITION - The standard addition technique
involves the use of the unknown and the unknown plus a known amount
of standard (Sect. 9.8.1).
3.7 LABORATORY REAGENT BLANK (LRB) (preparation blank) - An aliquot of
reagent water that is treated exactly as a sample including exposure
to all glassware, equipment, reagents, and acids that are used with
other samples. The LRB is used to determine if method analytes or
other interferences are present in the laboratory environment, the
reagents or apparatus (Sects. 7.5.2 and 10.3.1).
3.8 CALIBRATION BLANK - A volume of ASTM type I 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. 7.5.1).
3.9 STOCK STANDARD SOLUTION - A concentrated solution containing one
analyte prepared in the laboratory using assayed reference materials
or purchased from a reputable commercial source (Sect. 7.3). Stock
35
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standard solutions are used to prepare calibration solutions and
other needed analyte solutions.
3.10 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).
3.11 LABORATORY PERFORMANCE CHECK SOLUTION (LPC) - A solution of method
analytes, used to evaluate the performance of the instrument system
with respect to a defined set of method criteria (Sects. 7.8 and
9.6).
3.12 PLASMA SOLUTION - A solution that is used to determine the optimum
height above the work coil for viewing the plasma (Sects. 7.6 and
9.3.3).
3.13 TUNING SOLUTION - A solution which is used to determine acceptable
instrument performance prior to calibration and sample analyses
(Sects. 7.7 and 9.4).
3.14 SPECTRAL INTERFERENCE CHECK SOLUTION (SIC) - A solution of selected
method analytes of higher level 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. 7.9 and 9.7).
3.15 LABORATORY FORTIFIED BLANK (LFB) - An aliquot of reagent water 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 method performance is within
acceptable control limits (Sects. 7.11 and 10.3.2).
3.16 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 the concentrations found (Sect. 10.4).
3.17 FIELD DUPLICATES (FD1 AND FD2) - Two separate samples collected at
the same time and place under identical circumstances and treated
exactly the same throughout field and laboratory procedures.
Analyses of FD1 and FD2 give a measure of the precision associated
with sample collection, preservation, and storage, as well as with
laboratory procedure.
3.18 QUALITY CONTROL SAMPLE (QCS) - A solution of method analytes of
known concentrations which is used to fortify an aliquot of LRB
matrix. The QCS is obtained from a source external to the
36
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laboratory, and is used to check laboratory performance (Sects. 7.12
and 10.2.4).
4. INTERFERENCES
4.1 Several types of interference effects may contribute to inaccuracies
in the determination of an analyte by ICP-AES. They can be
summarized as follows:
4.1.1 Spectral interferences - Can be categorized as (1) overlap of
a spectral line from another element; (2) unresolved overlap
of molecular band spectra; (3) background contribution from
continuous or recombination phenomena; and (4) background
contribution from stray light from the line emission of high
concentration elements.1 The first of these effects can be
compensated by utilizing a computer correction of raw data,
requiring monitoring and measurement of the interfering
element. -3 The second effect may require selection of an
alternative wavelength. The third and fourth effects can
usually be compensated by a background correction adjacent to
the analyte line.
Given in Table 3 is a listing of the interelement spectral
interferences that can occur between method analytes when
using the recommended wavelengths and locations for back-
ground corrections listed in Table 1. Table 3 is not a
complete listing of all possible interelement interferences;
however, those not included are interferences from elements
either not readily solubilized by the sample preparation
procedures described in this method or from elements rare in
nature. The correction factors listed in Table 3 indicate
the magnitude of the interference. The factors were
experimentally determined at EMSL-Cincinnati using an
instrument with a specified wavelength dispersion of 0.53
nm/mm and a spectral bandpass resolution of 0.036 nm in the
first order. The factors have been rounded to the tenth-
thousand place or reported to one significant number. The
listing is presented as a guide for users of this method for
determining interelement interference effects. The reader is
cautioned that other analytical systems may exhibit somewhat
different levels of interference than those shown in Table 3
and that the interference effects must be evaluated for each
individual instrumental system.
The correction factors given in Table 3 were determined by
analyzing single element solutions of each interfering
element. The concentration of each single element solution
was within the LDR of that element. For most elements a
100 mg/L solution was used with the numerical value of most
correction factors being confirmed by analyzing lesser
dilutions of the single element solution. Because Ca, Fe, Mg
and Na can normally be present at concentrations in excess of
37
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4.1.2
100 mg/L, the interferences attributed to these elements were
determined at concentrations near their linear limits. The
criteria for listing a spectral interference was an apparent
analyte concentration from the interfering single element
solution that was outside the 95% confidence interval
estimates for the determined MDL limits4 of the analyte using
the 2x preconcentration procedure described in Sect. 11.2.1
(See Table 2). The correction factor was calculated by
dividing the blank subtracted apparent analyte concentration
by the determined concentration of the interfering element.
Positive values in Table 3 are interferences that occur on
the wavelength peaks, while negative values indicate an
interference at the location used for background correction.
In practice, during analysis, the correction factor is used
to calculate the apparent concentration from interfering
element and is then subtracted from the instrumental analyte
concentration to determine the net, or sample analyte
concentration (while positive values are subtracted, negative
values are actually added). Without these corrections when
interference effects are present, either false positive or
false negative determinations will result. Also, the
reliability of an applied correction depends on the variance
surrounding the measurement of the interfering element. As
the concentration of the interfering element increases, the
variance increases; this is reflected in the calculated
apparent analyte concentration. Extreme caution should be
exercised when reporting analyte concentrations where the
apparent analyte concentration from an interfering element
accounts for 90% of the measured analyte concentration. Once
a routine procedure for correcting interelement spectral
interferences has been established, it should be periodically
tested to evaluate its operational effectiveness and
continued reliability (Sect. 7.9).
Physical interferences - Are generally considered to be
effects associated with the sample nebulization and
transport processes. Such properties as change in viscosity
and surface tension can cause significant inaccuracies
especially in samples which may contain high dissolved solids
and/or high acid concentrations. The use of a peristaltic
pump may lessen these interferences. If these types of
interferences are operative, they must be reduced by sample
dilution and/or utilization of standard addition techniques
(Sect. 9.8). Another problem which can occur from high
dissolved solids is salt buildup at the tip of the nebulizer.
This affects aerosol flow rate causing instrumental drift.
Wetting the argon prior to nebulization, use of a tip washer,
or sample dilution have been used to control this problem.
Also, it has been reported that better control of the argon
flow rate improves instrument performance. This is
accomplished with the use of mass flow controllers.
38
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4.1.3 Chemical Interferences - Are characterized by molecular
compound formation, ionization effects and solute vaporiza-
tion effects. Normally these effects are not pronounced
with the ICP technique, however, if observed they can be
minimized by careful selection of operating conditions (i.e.,
incident power, observation position, etc.), by buffering the
sample, matrix matching, or standard addition procedures.
These types of interferences can be highly dependent on
matrix type and the specific analyte element.
4.1.4 Memory interferences - Result when analytes in a previous
sample contribute to the signals measured in a current
;: sample. Memory effects can result from sample deposition on
the uptake tubing to the nebulizer or from build-up 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. 7.5.3). 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
either their LDRs or concentrations 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 recommends a
rinse period of 60 sec between samples and standards. If a
memory interference is suspected, the sample should be
reanalyzed after a long rinse period.
4.2 The occurrence of interferences described in Sects. 4.1.1, 4.1.2 and
4.1.3 are primarily attributed to the sample matrix. If an
interference caused by a particular sample matrix is known, in many
cases it can be circumvented. However, when the nature of the
sample is unknown, tests as outlined in Sects. 4.2.1 through 4.2.4
can be used to ensure the analyst that neither positive nor negative
interference effects are operative on any of the analyte elements
thereby distorting the accuracy of the reported values.
4.2.1 Serial dilution - If the analyte concentration is
sufficiently high (minimally a factor of 10X the MDL after
dilution), an analysis of a dilution should agree within 10%
of the original determination or within an established
acceptable control limit.5 If not, a chemical or physical
interference effect should be suspected.
4.2.2 Analyte addition - A post digestion analyte addition added at
a minimum level of 20X the MDL (maximum 100X) to the original
39
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determination should be recovered to within 90% to 110% or
within an established control limit. If not, a matrix effect
should be suspected. The use of a standard addition analysis
procedure can usually compensate for this effect. CAUTION:
The standard addition technique does not detect coincident
spectral overlap. If suspected, use of computerized
compensation, an alternative wavelength, or comparison with
an alternative method is recommended (Sect. 4.2.3).
4.2.3 Comparison with alternative method of analysis - When
investigating a sample matrix, comparison tests may be
performed with other analytical techniques, such as atomic
absorption spectrometry, ICP-mass spectrometry, or other
approved methodology.
4.2.4 Wavelength scanning of analyte line region - If the appro-
priate equipment is available, wavelength scanning can be
performed to detect potential spectral interferences.
5. SAFETY
5.1 The toxicity or 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
as low as reasonably achievable. Each laboratory is responsible for
maintaining a current file of OSHA regulations regarding the safe
handling of 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 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.
5.2 Analytical plasma sources emit radiofrequency radiation and intense
UV radiation. Suitable precautions should be taken to protect
personnel from such hazards.
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 Precautions should also be taken to minimize potential hazards.
Basic good housekeeping and safety practices such as the use of
rubber or plastic gloves and safety glasses during cleaning of
labware are highly recommended.
6. APPARATUS AND EQUIPMENT
6.1 ANALYTICAL INSTRUMENTATION
40
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6.1.1 The ICP instrument may be a simultaneous or sequential
spectrometer system that uses ionized argon gas as the
plasma. However, the system and processing of background
corrected signals must be computer controlled. The
instrument must be capable of meeting and complying with the
requirements and description of the technique given in Sect.
2.1 of the method. In particular, it is the responsibility
of the analyst to investigate the spectral interference
(Sect. 4.1.1) operative about each analytical wavelength used
and to verify and periodically confirm that the instrument
configuration and operating conditions used satisfy the
analytical requirements.
6.1.2 Argon gas supply - Liquid, high purity grade (99.99%).
6.1.3 A variable speed peristaltic pump is required to deliver both
standard and sample solutions to the nebulizer.
6.1.4 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.
6.1.5 For routine analyses of solutions containing dissolved solids
>1%, a high solids nebulizer and a torch injector tube having
an i.d. >1.0 mm are recommended. (Consult the instrument
manufacturer for guidance.)
6.1.6 For sustained analyses of solutions containing alkali
concentrations >0.5%, an alumina torch injector tube is
recommended to prevent devitrification of the normally-used
quartz injector tube.
NOTE: Regular periodic cleaning of the quartz torch assembly
and injector tube by soaking in aqua regia (Sect. 7.1.9)
reduces background signal noise, calibration drift and
potential memory effects.
6.2 SAMPLE PROCESSING EQUIPMENT
6.2.1 Air Displacement Pipetter: Digital pipet capable of
delivering volumes ranging from 0.1 to 2500 #L with an
assortment of high quality disposable pipet tips.
6.2.2 Hot Plate: Ceramic top, graduated dial 90°C to 450°C
(Corning PC100 or equivalent).
6.2.3 Single pan balance: Balance capable of weighing to the
nearest 0.01 g.
41
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6.2.4 Analytical balance: Balance capable of weighing to the
nearest 0.0001 g.
6.2.5 Centrifuge: Steel cabinet with guard bowl, electric timer
and brake. (International Centrifuge, Universal Model UV or
equivalent.)
6.2.6 Drying oven: Gravity convection oven, with thermostatic
control capable of maintaining 180°C ± 5°C.
6.3 LABWARE - For the 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 con-
centrations through adsorption processes. All reuseable labware
(glass, quartz, polyethylene, Teflon, etc.), including the sample
container, should be cleaned prior to use. Labware should be soaked
overnight and thoroughly washed with laboratory-grade detergent and
water, rinsed with water, and soaked for four hours in a mixture of
dilute nitric and hydrochloric acid (1+2+9), followed by rinsing
with water, ASTM type I water, and oven drying.
NOTE: Chromic acid must not be used for cleaning glassware.
6.3.1 Glassware - Volumetric flasks, graduated cylinders, funnels
and centrifuge tubes (glass and/or metal-free plastic).
6.3.2 Assorted calibrated pipettes.
6.3.3 Conical Phillips beakers, 250-mL with 50-mm watch glasses.
Griffin beakers, 250-mL with 75-mm watch glasses. Teflon
and/or quartz beakers, 250-mL with Teflon covers (optional).
6.3.4 Wash bottle - One piece stem, Teflon FEP bottle with Tefzel
ETFE screw closure, 125-mL capacity.
7. REAGENTS AND CONSUMABLE MATERIALS
7.1 Reagents may contain elemental impurities which might affect
analytical data. Only 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.
7.1.1 Nitric acid, concentrated (sp.gr. 1.41) (CASRN 7697-37-2).
42
-------
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 Nitric acid (1+9) - Add 100 ml cone, nitric acid to 400 ml of
ASTM type I water and dilute to 1 L.
7.1.4 Hydrochloric acid, concentrated (sp.gr. 1.19) (CASRN 7647-01-
0).
7.1.5 Hydrochloric acid (1+1) - Add 500 ml cone, hydrochloric acid
to 400 ml of ASTM type I water and dilute to 1 L
7.1.6 Hydrochloric acid (1+4) - Add 200 ml cone, hydrochloric acid
to 400 ml ASTM type I water and dilute to 1 L.
7.1.7 Ammonium hydroxide, concentrated (sp. gr. 0.902) (CASRN 1336-
21-6).
7.1.8 Tartaric acid, ACS reagent grade (CASRN 87-69-4).
7.1.9 Aqua regia - Add 100 ml cone, nitric acid to 300 ml cone.
hydrochloric acid and 100 ml ASTM type I water.
7.2 WATER - For all sample preparation and dilutions, ASTM type I water
(ASTM D1193) is required. Suitable water maybe prepared by
passing distilled water through a mixed bed of anion and cation
exchange resins.
7.3 STANDARD STOCK SOLUTIONS - 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 one
hour at 105°C, unless otherwise specified. (CAUTION: Many metal
salts are extremely toxic if inhaled or swallowed. Wash hands
thoroughly after handling). Stock solutions should be stored in
Teflon bottles.
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 jug Al: Pickle aluminum
metal in warm (1+1) hydrochloric acid to an exact weight of
0.100 g. Dissolve in 10 ml cone, hydrochloric acid and 2 ml
cone, nitric acid, heating to effect solution. Continue
heating until volume is reduced to 4 ml. Cool and add 4 ml
43
-------
ASTM type I water. Heat until volume is reduced to 2 mL.
Cool and dilute to 100 mL with ASTM type I water.
7.3.2 Antimony solution, stock 1 mL = 500 /ig Sb: Dissolve 0.100 g
Sb powder in 2 mL (1+1) nitric acid and 1.0 mL cone.
hydrochloric acid. Add 10 mL ASTM type I water and 0.15 g
tartaric acid. Warm slightly to effect complete solution.
Cool and dilute to 200 mL with ASTM type I water.
7.3.3 Arsenic solution, stock 1 mL = 1000 p,g As: Dissolve 0.1320 g
As203 in a mixture of 50 mL ASTM type I 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 ASTM type I water.
7.3.4 Barium solution, stock 1 mL = 500 /Ltg Ba: Dissolve 0.1437 g
BaC03 in a solution mixture of 10 mL ASTM type I water and 5
mL cone, nitric acid. Heat and stir to effect solution and
degassing. Dilute to 200 mL with ASTM type I water.
7.3.5 Beryllium solution, stock 1 mL = 500 jLig Be: Dissolve 1.965 g
BeS04.4H20 (DO NOT DRY) in 50 mL ASTM Type I water. Add 2 mL
cone, nitric acid. Dilute to 200 mL with ASTM type I water.
7.3.6 Boron solution, stock 1 mL = 1000 fig B: DO NOT DRY.
Dissolve 0.5716 g anhydrous H3B03 in 20 mL ASTM type I water.
Dilute to 100 mL with ASTM type I water, mix and immediately
transfer to a Teflon bottle for storage. Use a reagent
meeting ACS specifications, keep the bottle tightly stoppered
and store in a desiccator to prevent the entrance of
atmospheric moisture.
7.3.7 Cadmium solution, stock 1 mL = 1000 /itg 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 ASTM type I water.
7.3.8 Calcium solution, stock 1 mL = 1000 p.g Ca: Suspend 0.2498 g
CaC03 dried at 180°C for 1 hour before weighing, in 20 mL of
ASTM type I water. Dissolve cautiously (reaction is
vigorous) by adding dropwise, 10 mL (1+1) hydrochloric acid.
Dilute to 100 mL with ASTM type I water.
7.3.9 Chromium solution, stock 1 mL = 500 /xg Cr: Dissolve 0.1923g
Cr03 in a solution mixture of 10 mL ASTM type I water and 2
mL cone, nitric acid.
water.
Dilute to 200 mL with ASTM type I
7.3.10 Cobalt solution, stock 1 mL = 1000 /ng Co: Pickle cobalt
metal in (1+9) nitric acid to an exact weight of 0.100 g.
44
-------
Dissolve in 5 ml (1+1) nitric acid, heating to effect
solution. Cool and dilute to 100 ml with ASTM type I water.
7.3.11 Copper solution, stock 1 mL = 1000 /zg 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 ASTM type I water.
7.3.12 Iron solution, stock, 1 ml = 1000 jzg Fe: Pickle iron metal
in (1+1) hydrochloric acid to an exact weight of 0.100 g.
Dissolve in 10 ml (1+1) hydrochloric acid, heating to effect
solution. Cool and dilute to 100 mL with ASTM type I water.
7.3.13 Lead solution, stock 1 mL = 1000 /zg Pb: Dissolve 0.1599 g
PbN03 in 5 mL (1+1) nitric acid. Dilute to 100 mL with ASTM
type I water.
7.3.14 Lithium solution, stock 1 mL = 500 jug Li: Dissolve 0.5324 g
Li?C03 in 20 mL ASTM type I water. Add 2 mL cone, nitric
acid and dilute to 200 mL with ASTM type I water.
7.3.15 Magnesium solution, stock 1 mL = 1000 /zg Mg: Dissolve
0.100 g cleanly polished magnesium ribbon in 5 mL (1+1)
hydrochloric acid. (Add acid slowly, reaction is vigorous)
Add 2 mL (1+1) nitric acid and dilute to 100 mL with ASTM
type I water.
7.3.16 Manganese solution, stock 1 mL = 1000 /zg Mn: Pickle
manganese flake 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 ASTM type I
water.
7.3.17 Mercury solution, stock 1 mL = 500 /zg Hg: DO NOT DRY, highly
toxic, poison. Dissolve 0.1354 g HgCl, in 20 mL ASTM type I
water. Add 10 mL cone, nitric acid and dilute to 200 mL with
ASTM type I water.
7.3.18 Molybdenum solution, stock 1 mL = 1000 /zg Mo: Dissolve
0.1500 g Mo03 in a solution mixture of 10 mL ASTM type I
water and 1 mL cone, ammonium hydroxide, heating to effect
solution. Cool and dilute to 100 mL with ASTM type I water.
7.3.19 Nickel solution, stock 1 mL = 1000 /zg Ni: Dissolve 0.100 g
nickel powder in 5 mL cone, nitric acid, heating to effect
solution. Cool and dilute to 100 mL with ASTM type I water.
7.3.20 Phosphorus solution, stock 1 mL = 1000 /zg P: Dissolve
0.3745 g NH4H2P04 in 20 mL ASTM type I water. Dilute to 100
mL with ASTM type I water.
45
-------
7.3.21 Potassium solution, stock, 1 ml = 1000 M9 K: Dissolve
0.1907 g KC1, previously dried at 110°C for 3 hrs in 20 ml
ASTM type I water. Add 2 mL (1+1) hydrochloric acid and
dilute to 100 ml with ASTM type I water.
7.3.22 Selenium solution, stock 1 ml = 500 jug Se: Dissolve 0.1405 g
Se02 in 20 ml ASTM type I water. Dilute to 200 ml with ASTM
type I water.
7.3.23 Silica solution, stock, 1 ml = 1000 /ug Si02: Do not dry.
Dissolve 0.2964 g NH4SiF6 in 20 ml solution mixture of ASTM
type I water and 1 ml cone, hydrochloric acid, heating at
85°C for 5 min to effect solution. Cool, dilute to 100 ml
with ASTM type I water, mix and immediately transfer to
Teflon bottle for storage.
7.3.24 Silver solution, stock 1 ml = 250 p.g Ag: Dissolve 0.125 g
silver metal in 10 ml (1+1) nitric acid, heating to effect
solution. Cool and dilute to 500 ml with ASTM type I water.
Store in amber container.
7.3.25 Sodium solution, stock 1 ml = 1000 p.g Na: Dissolve 0.2542 g
NaCl in 20 mL ASTM type I water. Add 2 ml (1+1) nitric acid
and dilute to 100 ml with ASTM type I water.
7.3.26 Strontium solution, stock 1 mL = 500 /ug Sr: Suspend 0.1685 g
SrC03 in 20 mL ASTM type I water. Dissolve continuously by
adding dropwise 10 mL (1+1) hydrochloric acid. Dilute to 200
mL with ASTM type I water.
7.3.27 Thallium solution, stock 1 mL = 500 jig Tl: Dissolve 0.1303 g
T1N03 in a solution mixture of 10 mL ASTM type I water and 2
mL cone, nitric acid. Dilute to 200 mL with ASTM type I
water.
7.3.28 Tin solution, stock 1 mL = 1000 /jg Sn: Dissolve 0.100 g Sn
shot in 20 mL (1+1) hydrochloric acid, heating to effect
solution. Cool and dilute to 100 mL with (1+1) hydrochloric
acid.
7.3.29 Vanadium solution, stock 1 ml = 1000 >tg 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 ASTM type I water.
7.3.30 Yttrium solution, stock 1 mL = 1000 /jg Y: Dissolve 0.1270 g
Y20, in 5 mL (1+1) nitric acid, heating to effect solution.
Cool and dilute to 1000 mL with ASTM type I water.
7.3.31 Zinc solution, stock 1 mL = 500 jitg Zn: Pickle zinc metal in
(1+9) nitric acid to an exact weight of 0.100 g. Dissolve in
46
-------
10 ml (1+1) nitric acid, heating to effect solution.
and dilute to 200 ml with ASTM type I water.
Cool
7.4 MIXED CALIBRATION STANDARD (CAL) SOLUTIONS—Prepare mixed CAL
solutions (Sects. 7.4.1 thru 7.4.5) by combining appropriate volumes
of the stock standard solutions in 500-mL volumetric flasks.
First, add 20 mL of (1+1) nitric acid and 20 mL of (1+1)
hydrochloric acid, then add the appropriate stock standard aliquots
and dilute to 500 mL with ASTM type I water. Prior to preparing the
mixed CAL solutions, each stock solution should be analyzed
separately to determine the presence of impurities. Transfer the
freshly prepared mixed CAL solutions to an acid clean, not
previously used FEP fluorocarbon or polyethylene bottles for
storage. Fresh mixed CAL solutions should be prepared as needed
with the realization that concentration can change on aging. The
CAL solutions must be initially verified using a quality control
sample and monitored weekly for stability (Sect. 7.12). Although
not specifically required, the listed CAL solution combinations
should be followed when using the specific wavelengths and
recommended background correction locations listed in Table 1. If
different combinations are used, the mixture should be verified for
compatibility, stability and absence of spectral interference
between analytes. This same requirement would apply if different
wavelengths and/or background correction locations are utilized.
7.4.1 CAL Solution I (Volume = 500.0 mL)
Analvte
Ag
As
B
Ba
Ca
Cd
Cu
Mn
Sb
Se
Stock
Solution
7.3.24
7.3.3
7.3.6
7.3.4
7.3.8
7.3.7
7.3.11
7.3.16
7.3.2
7.3.22
Aliquot
Vol. mL
1.0
5.0
1.0
1.0
5.0
1.0
1.0
1.0
5.0
5.0
Analyte
Cone. uq/mL
0.5
10.0
2.0
1.0
10.0
2.0
2.0
2.0
5.0
5.0
NOTE: If the addition of silver to the recommended
acid combination results in an initial precipitation, add
15 mL of ASTM type I water and warm the flask until the
solution clears. For the acid concentration used in the
CAL solutions, the silver concentration should be limited
to 0.5 mg/L. Higher concentrations of silver require
additional hydrochloric acid.
47
-------
7.4.2 CAL Solution II (Volume = 500.0 ml)
Analvte
K
Li
Mo
Na
Sr
Stock
Solution
7.3.21
7.3.14
,18
.25
7.3.
7.3,
7.3.26
Aliquot
Vol. ml
10.0
5.0
5.0
5.0
1.0
Analyte
Cone, uq/ml
20.0
5.0
10.0
10.0
1.0
7.4.3 CAL Solution III (Volume = 500.0 mL)
Aliquot
Vol. mL
1.0
1.0
5.0
500.0 mL)
Aliquot
Vol. mL
5.0
5.0
2.0
5.0
2.0
5.0
Analvte
Co
V
P
7.4.4 CAL Solution
Analvte
Al
Cr
Hg
Si02
Sn
Zn
">Stock
Solution
7.3.10
7.3.29
7.3.20
IV (Volume
Stock
Solution
7.3.1
7.3.9
7.3.17
7.3.23
7.3.28
7.3.31
Analyte
Cone. uq/mL
2.0
2.0
10.0
Analyte
Cone. uq/mL
10.0
5.0
2.0
10.0
4.0
5.0
7.4.5 CAL Solution V (Volume = 500.0 mL)
Analvte
Be
Fe
Mg
Ni
Pb
Tl
Stock
Solution
7.3.5
7.3.12
7.3.15
7.3.19
7.3.13
7.3.27
Aliquot
Vol. mL
,0
.0
,0
.0
5.0
5.0
Analyte
Cone. uq/mL
1.0
10.0
10.0
2.0
10.0
5.0
7.5 BLANKS - Three types of blanks are required for this method. A
calibration blank is used to establish the analytical calibration
curve, a laboratory reagent blank is used to assess possible
contamination from the sample preparation procedure and a rinse
48
-------
blank is used to flush the instrument uptake system and nebulizer
between standards and samples to reduce memory interferences.
7.5.1 Calibration blank - Prepare by diluting a mixture of 20 ml of
(1+1) nitric acid and 20 ml of (1+1) hydrochloric acid to 500
ml with ASTM type I water. Store in a Teflon bottle.
7.5.2 Laboratory reagent blank (LRB) - Contains all the reagents in
the same volumes used in processing the samples. The LRB
must be carried through the entire preparation procedure and
analysis scheme. The final solution should contain the same
acid concentrations as sample solutions for analysis.
7.5.3 Rinse blank - Prepare this acid wash solution in the same
manner as the calibration blank and store in a convenient
manner.
7.6 PLASMA SOLUTION - This solution is used for determining the optimum
viewing height of the plasma above the work coil prior to using the
method (Sect. 9.3.3). The solution is prepared by adding a 5 mL
aliquot from each of the stock standard solutions of arsenic
(Sect. 7.3.3) and lead (Sect. 7.3.13), and a 10 mL aliquot from each
of the stock standard solutions of selenium (Sect. 7.3.22) and
thallium (Sect. 7.3.27), to a mixture of 20 mL (1+1) nitric acid and
20 mL (1+1) hydrochloric acid and diluting to 500 mL with ASTM type
I water. Store in a Teflon bottle.
7.7 TUNING SOLUTION - This solution is used for adjusting the aerosol
argon gas flow prior to calibration and analysis (Sect. 9.4). The
solution is prepared by adding a 5 mL aliquot from each of the stock
standard solutions of copper (Sect. 7.3.11) and lead (Sect. 7.3.13)
to a mixture of 20 mL (1+1) nitric acid and 20 mL (1+1) hydrochloric
acid and diluting to 500 mL with ASTM type I water. Store in a
Teflon bottle.
7.8 LABORATORY PERFORMANCE CHECK (LPC) SOLUTION - This solution is
prepared by adding the following listed aliquot volumes of the
individual stock standards to the mixture of 20 mL (1+1) nitric acid
and 20 mL (1+1) hydrochloric acid and diluting to 500 mL with ASTM
type I water. Immediately transfer the freshly prepared LPC to an
acid cleaned, not previously used, Teflon bottle.
Stock Aliquot Analyte
Analvte Solution Vol. mL Cone. uq/mL
Ag 7.3.24 1.0 0.5
Al 7.3.1 1.0 2.0
As 7.3.3 1.0 2.0
B 7.3.6 1.0 2.0
Ba 7.3.4 2.0 2.0
Be 7.3.5 2.0 2.0
49
-------
Ca
Cd
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
P
Pb
Sb
Se
Si02
Sn
Sr
Tl
V
Zn
7.3.8
7.3.7
7.3.10
7.3.9
7.3.11
7.3.12
7.3.17
7.3.21
7.3.14
7.3.15
7.3.16
7.3.18
7.3.25
7.3.19
7.3.20
7.3.13
7.3.2
7.3.22
7.3.23
7.3.28
7.3.26
7.3.27
7.3.29
7.3.31
2.0
5.0
1.0
5.0
1.
2,
0
0
2.0
5.0
1.0
2.0
2.0
1.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
10.0
.0
.0
.0
.0
.0
2.0
10.0
2.0
2.0
2.0
10.0
.0
.0
.0
2.0
2.0
2.
2.
2.
2.
2,
2.
2.
2.
7.9 SPECTRAL INTERFERENCE CHECK (SIC) SOLUTIONS - Once the interelement
spectral interference correction factors have been determined (Sect.
4.1.1) and the procedural routine for their use has been
established, the operative process should be periodically tested and
updated as needed. It is usually not practical to test and update
the entire corrective process on a daily or weekly basis. The
frequency of confirming and/or updating the entire corrective
process is the responsibility of the analyst and should be dictated
by instrument stability, type of samples analyzed and the expected
interference encountered. The following procedure is recommended
for testing and verifying the interelement spectral correction
process. A general description of the procedure is given in
Sect. 7.9.1. In Sect. 7.9.2 thru 7.9.4 instructions are given for
the preparation of SIC solutions that are specific to the
wavelengths and background correction locations given in Table 1.
The SIC solutions are designed to monitor and detect a 10% change in
a partial list of the interference correction factors given in Table
3. The factors selected for monitoring were determined by dividing
each of the listed correction factors by 10 and multiplying the
quotient by the concentration of the interfering element in the
respective SIC solution given below. If the resulting product was a
number equal to or greater than two times the analyte MDL, the
correction factor was included for monitoring.
7.9.1 Prepare an acid matrix solution of the interfering element at
a high level of concentration (e.g., 50 mg/L). Complete 10
analyses of the solution and determine the standard deviation
50
-------
of the mean concentration. From the data calculate a
concentration equal to 4.52 times the standard deviation.
(This calculated concentration estimates the 95% confidence
interval of the interferent mean concentration). Multiply
the calculated concentration by the correction factor to be
tested. Disregarding the numerical sign of the product, add
a concentration value equivalent to 2.2X the MDL of the
analyte that is being corrected. The sum of the two
concentrations, when bisected by the calibration blank,
describes an acceptable apparent analyte concentration range.
If the apparent analyte concentration from the analysis of
the interferent solution is within the acceptable range, the
correction process is considered to be in control. If the
apparent analyzed concentration is outside the range, as
either a positive or negative concentration, a change in the
correction process is indicated and an update of the process
may be required.
NOTE: The interfering solution should be analyzed more than
once to confirm a change occurred with adequate rinse time
between solutions and before the subsequent analysis of the
calibration blank.
7.9.2 SIC solution I (50 mg/L Mo) - Add a 5 ml aliquot of the stock
standard solution of molybdenum (Sect. 7.3.18) to a mixture
of 4 ml (1+1) nitric acid and 4 ml (1+1) hydrochloric acid
and dilute to 100 ml with ASTM type I water. Store in a
Teflon bottle. This solution is used to evaluate the
molybdenum interelement spectral correction factors on the
analytes: Al, Sb, Se, Sn, and V. (See Table 3).
7.9.3 SIC solution II (10 mg/L Co; 20 mg/L Cr, Mn and V; and 40
mg/L Cu) - Add a 1 mL aliquot from the stock standard
solution of cobalt (Sect. 7.3.10), a 2 mL aliquot from each
of the stock standard solutions of manganese (Sect. 7.3.16)
and vanadium (Sect. 7.3.29) and a 4 mL aliquot from the stock
standard solutions of chromium (Sect. 7.3.9) and copper
(7.3.11) to a mixture of 4 mL (1+1) nitric acid and 4 mL
(1+1) hydrochloric acid and dilute to 100 mL with ASTM Type I
water. Store in a Teflon bottle. This solution is used to
evaluate the following list of interelement spectral
correction factors (See Table 3).
Analvte Interferent
Pb Co
Sb Cr
Mo Mn
As V
Be V
Zn Cu
51
-------
7.9.4
SIC Solution III (20 mg/L Ni, 30 mg/L Al and 150 mg/L Fe) -
Add a 2 ml aliquot from the stock standard solution of nickel
(Sect. 7.3.19), a 3 ml aliquot from the stock standard
solution of aluminum (Sect. 7.3.1) and a 15 ml aliquot from
the stock standard solution of iron (Sect. 7.3.12) to a
mixture of 4 mL (1+1) nitric acid and 4 ml (1+1) hydrochloric
acid and dilute to 100 ml with ASTM Type 1 water. Store in a
Teflon bottle. This solution is used to evaluate the
following list of interelement spectral correction factors
(See Table 3).
Analvte
Sb
In
As
Ag
Cr
Mn
V
Interferent
Ni
Ni
Al
Fe
Fe
Fe
Fe
.10 LABORATORY FORTIFYING STOCK SOLUTION - This solution is used in
preparing the laboratory fortified blank and the laboratory
fortified sample matrix. Prepare the solution in a 200-mL
volumetric flask by adding the following listed aliquot volumes of
the individual stock solutions to a mixture of 4 mL (1+1) nitric
acid and 20 mL (1+1) hydrochloric acid. Dilute to the mark with
ASTM type I water. Transfer the freshly prepared solution to a
Teflon bottle for storage.
Stock
Analvte
Ag
Al
As
B
Ba
Be
Cd
Co
Cr
Cu
Fe
Hg
Li
Mn
Mo
Ni
P
Pb
Aliquot
Solution
7.3,
7.3,
,24
.1
7.3.3
7.3.6
7.3.4
7.3.5
7.3.7
,10
.3.9
,11
,12
7.3.
7.
7.3.
7.3.
7.3.
7.3.
7.3.
7.3,
7.3,
7.3.
17
14
16
18
19
20
7.3.13
Analyte
Vol. mL
2.0
5.0
5.0
5.0
10.0
2.0
2.0
2.0
10.0
5.0
5.0
2.0
10.0
5.0
2.0
5.0
10.0
5.0
Cone. ug/mL
2.5
25
25
25
25
5
10
10
25
25
25
5
25
25
10
25
50
25
52
-------
Sb
Se
Si02
Sn
Sr
Tl
V
Zn
7.3.2
7.3.22
7.3.23
28
7.3
7.3
7.3
,26
27
7.3.29
7.3.31
10.0
10.0
5.0
2.0
10.0
10.0
2.0
10.0
25
25
25
10
2S
25
10
25
NOTE: The analytes Ca, K, Mg, and Na are not included in the
fortifying stock solution because their concentrations vary
widely in environmental samples. The analytes B and Si02
should be disregarded if samples are processed and diluted in
borosilicate labware because of the known contamination that
occurs from borosilicate glass.
7.11 LABORATORY FORTIFIED BLANK (LFB) - To a 100 mL aliquot of ASTM type
water add 2 mL of (1+1) nitric acid, 1.0 mL (1+1) hydrochloric acid
and 2 mL of the laboratory fortifying stock solution (Sect. 7.10).
The LFB must be carried through the entire sample preparation
procedure and analysis scheme. The final solution should be diluted
to 50 mL as are the samples. Listed below is the expected
concentration of each analyte based on the original 100 mL of water.
Analvte
Ag
Al
As
B
Ba
Be
Cd
Co
Cr
Cu
Fe
Hg
Li
Mn
Mo
Ni
P
Pb
Sb
Se
Si02
Sn
Sr
Tl
V
Zn
Cone. uq/mL
0.05
0.5
0.5
0.5
0.5
0.1
0.2
0.2
0.5
0.5
0.5
0.1
0.5
0.5
0.2
0.5
1.0
0.5
0.5
0.5
0.5
0.2
0.5
0.5
0.2
0.5
53
-------
7.12 QUALITY CONTROL SAMPLE - The quality control sample (Sect. 3.18)
should be prepared in the same acid matrix as the calibration
standards at a concentration near 1 mg/L, except silver, which must
be limited to a concentration of 0.5 mg/L. Follow the instructions
provided by the supplier and store the sample in a Teflon bottle.
The Quality Assurance Research Division of EMSL-Cincinnati will
either supply a quality control sample or provide information where
one of equal quality can be procured.
8. SAMPLE COLLECTION. PRESERVATION AND STORAGE
8.1 Prior to 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. Filtration, acid preservation, etc., should be
performed at the time of sample collection or as soon thereafter as
practically possible.
8.2 For determination of dissolved elements, the sample must be filtered
through a 0.45-/im membrane filter. (Glass or plastic filtering
apparatus is recommended to avoid possible contamination. Only
plastic apparatus should be used when determination of boron or
silica is critical (Sect.1.6). 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 a pH < 2.
8.3 For the determination of total recoverable elements in aqueous
samples, acidify with (1+1) nitric acid at the time of collection to
a pH < 2 (normally, 3 mL of (1+1) acid per liter of sample is
sufficient for most ambient and drinking water samples). The sample
should not be filtered prior to analysis (Sect. 1.6).
NOTE: Samples that cannot be acid preserved at the time of
collection because of sampling limitations or transport restrictions
should be acidified with nitric acid to a pH < 2 upon receipt in
the laboratory. Following acidification, the sample should be held
for 16 hours before withdrawing an aliquot for sample processing.
8.4 Solid samples usually require no preservation prior to analysis
other than storage at 4°C.
9. CALIBRATION AND STANDARDIZATION
9.1 Recommended wavelengths and background correction locations are
listed in Table 1. Other wavelengths and background correction
locations may be substituted if they can provide the needed
sensitivity and are corrected for spectral interference. In Table 4
specific instrument operating conditions are recommended. However,
because of the difference among various makes and models of spectro-
meters, the analyst should follow the instrument manufacturer's
54
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instructions, and if possible, approximate the recommended operating
conditions.
9.2 Allow the instrument to become thermally stable before beginning.
This usually requires at least 30 min of operation prior to plasma
optimization, plasma tuning and/or calibration.
9.3 PLASMA OPTIMIZATION - Prior to the use of this method optimize the
plasma operating conditions using the following procedure. 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.
9.3.1 Select an appropriate incident rf power with minimum
reflected power (see Table 4 for recommendations) and
aspirate the 1000 fig/ml solution of yttrium (Sect. 7.3.30).
Following the instrument manufacturer's instructions 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.
9.3.2 After establishing the nebulizer gas flow rate, determine the
solution uptake rate of the nebulizer in mL/min by aspirating
a known volume acid blank for a period of at least 3 min.
Divide the spent volume by three and record the uptake rate.
Set the peristaltic pump to deliver the uptake rate in a
steady even flow.
9.3.3 After horizontally aligning the plasma and/or optically
profiling the spectrometer, use the selected instrument
conditions from Sects. 9.3.1 and 9.3.2, and aspirate the
plasma solution (Sect. 7.7), containing 10 jug/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.)12 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 best compromise of intensity ratios of all four analytes.
9.3.4 The instrument operating condition finally selected as being
optimum should provide the lowest reliable IDLs and MDLs
similar to those listed in Table 2.
55
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9.3.5 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.
9.3.6 Before daily calibration and after the instrument warm-up
period (Sect. 9.2), the nebulizer gas flow must be reset to
the determined optimized flow. If a mass flow controller is
being used, it should be either reset to the recorded
optimized flow-rate or the optional plasma tuning procedure
given in Sect. 9.4 should be followed to reconfigure the
plasma. In order to provide and maintain valid interelement
spectral correction factors the nebulizer gas flow rate must
be well controlled. 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 nn) lines is illustrated in
Figure 1.
9.4 PLASMA TUNING (Optional) - This procedure can be used on a daily
basis to collect the data necessary for fine tuning the plasma to a
set Cu/Pb concentration ratio that reflects the optimized conditions
determined in Sect. 9.3. The analytical zone of the plasma can be
altered by varying the aerosol carrier gas flow entering the plasma.
This procedure requires the use of a mass flow controller for
adjusting the nebulizer gas flow rate to reset the Cu/Pb
concentration ratio. (This procedure can be used even when the
front surface entrance optics degrade in a non-uniform manner over
the visible and ultraviolet wavelength regions.)
9.4.1 Set the instrument to the optimized operating conditions
(Sect. 9.3). After instrument warm-up, horizontal alignment
of the plasma and/or optical profiling of the spectrometer,
aspirate the tuning solution (Sect. 7.7) and collect 10
replicate measurements of the Cu (324.75 nm) and Pb (220.35
nm) intensity signals at every 25 mL/min interval over the
flow rate range of 500 to 800 mL/min. Repeat the operation
using the calibration blank solution. Subtract the
respective mean blank value and calculate the net mean
intensity value for both metals at each flow rate. Plot the
net mean intensity values versus flow rate as illustrated in
Figure 1. From the plot determine the maximum signal
intensity flow rate for each metal.
9.4.2 To determine the Cu/Pb concentration ratio, set the
instrument to the optimized operating conditions. After
warm-up and optical profiling, calibrate the instrument for
both Cu (324.75 nm) and Pb (220.35 nm) at their respective
maximum intensity flow rates (See Figure 1, Cu 750 mL/min, Pb
535 mL/min) with the calibration blank set at the optimum
flow (e.g., 620 mL/min).
56
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9.4.3 Reset the nebulizer gas flow to the rate established in Sect.
9.3.1 (e.g., 620 mL/min) and collect data from 10 replicate
analyses of the tuning solution (Sect. 7.6). Ratio the
determined copper concentration to the determined lead
concentration on each analysis and compute the standard
deviation and mean value of the 10 ratios. (Note: Disregard
the fact that the determined concentrations do not equal the
prepared concentrations of the tuning solution.) The mean
value is used for resetting the ratio on a daily basis.
9.4.4 For tuning the plasma on a daily basis calibrate the
instrument as described in Sect. 9.4.2. Reset the nebulizer
gas flow rate to the optimum flow (e.g. 620 mL/min) and
analyze the tuning solution. Calculate the Cu/Pb
concentration ratio from the analysis. If the calculated
ratio is not within two standard deviations of the mean value
established in Sect. 9.4.3, adjust the nebulizer gas flow and
reanalyze the tuning solution until the ratio is within
range. Lowering the gas flow rate will increase the lead
concentration, decrease the copper concentration, and,
therefore, lower the ratio. The opposite is true when the
gas flow is increased. Day-to-day variations in the
nebulizer gas flow should be < ± 10 mL/min. Larger changes
should alert the analyst to possible instrumental problems.
9.4.5 Once an acceptable ratio is achieved, the instrument is ready
for analytical calibration.
9.4.6 If either the selected instrument operating conditions are
changed or instrument components replaced that require the
plasma to be reoptimized (Sect. 9.3.5), the Cu/Pb
concentration ratio must be reestablished.
9.5 CALIBRATION - Calibrate the instrument according to the instrument
manufacturer's instructions using the prepared calibration blank
(Sect. 7.5.1) and CAL solutions (Sect. 7.4). The following
operational steps should be used for both CAL solutions and samples.
9.5.1 Using a peristaltic pump introduce the standard or sample to
nebulizer at a uniform rate (e.g., 1.2 mL/min).
9.5.2 To allow equilibrium to be reached in the plasma, aspirate
the standard or sample solution for 30 sec after reaching the
plasma before beginning integration of the background
corrected signal.
9.5.3 When possible use the average value of four 5 sec background
corrected integration periods as the atomic emission signal
to be correlated to analyte concentration.
9.5.4 Between each standard^or sample, flush the nebulizer and
solution uptake system with the rinse blank acid solution
57
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(Sect. 7.5.3) for 60 sec or for the required period of time
to ensure that analyte memory effects are not occurring.
9.6 Analyze the LPC solution (Sect. 7.8) and calibration blank (Sect.
7.5.1) immediately following calibration, after every tenth sample
and at the end of the sample run. The analyzed value of each
analyte in the LPC solution should be within 95% to 105% of its
expected value. If an analyte value is outside the interval,
reanalyze the LPC. If the analyte is again outside the ± 5% limit,
the instrument should be recalibrated and all samples following the
last acceptable LPC solution should be reanalyzed.
9.7 Periodically verify the validity of the interelement spectral
interference correction process. The frequency of this testing is
the responsibility of the analyst, however, confirmation prior to
analysis of solid sample extracts is particularly useful. See Sect.
7.9 for guidance and criteria.
9.8 If methods of standard addition are required, the following
procedure is recommended.
9.8.1 The standard addition technique13 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 constitu-
ent 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
that causes a baseline shift. The simplest version of this
technique is the single-addition method. The procedure is
as follows. Two identical aliquots (Volume Vx) of the sample
solution, 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 non-analyte signals.
The unknown sample concentration cx is calculated:
Cx =
cs
-------
1. The analytical curve must be linear.
2. The chemical form of the analyte added must respond the
same 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 interfer-
ence.
10. QUALITY CONTROL
10.1 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 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
data generated.
10.2 INITIAL DEMONSTRATION OF PERFORMANCE.
10.2.1 The initial demonstration of performance is used to
characterize instrument performance (MDLs and linear calibra-
tion ranges) and laboratory performance (analysis of quality
control sample) for analyses conducted by this method.
10.2.2 MDLs should be established for all analytes, using reagent
water (blank) fortified at a concentration of two to three
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.
MDLs should be determined every six months or whenever there
is a significant change in the background or instrument
response.
10.2.3 Linear calibration ranges - The upper limit of the linear
calibration range should be established for each analyte by
determining the signal responses from a minimum of three
59
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different concentration standards, one of which is close to
the upper limit of the linear range. The linear calibration
range which may be used for the analysis of samples should be
judged by the analyst from the resulting data. Linear
calibration ranges should be determined whenever there is a
significant change in instrument response and every six
months for those analytes that periodically approach their
linear limit.
10.2.4 Quality Control Sample (QCS) - When beginning the use of this
method and on a quarterly basis, verify acceptable laboratory
performance with the preparation and analyses of a quality
control sample (Sect. 7.12). The QCS is carried through the
entire analytical operation of the method. If the determined
concentrations are not within ± 5% of the stated values of 1
mg/L, laboratory performance is unacceptable. The source of
the problem should be identified and corrected before
continuing analyses.
10.3 ASSESSING LABORATORY PERFORMANCE - REAGENT AND FORTIFIED BLANKS
10.3.1 Laboratory reagent blank (LRB) - The laboratory must analyze
at least one LRB (Sect. 7.5.2) with each set of samples. LRB
data are used to assess contamination from the laboratory
environment. If an analyte value in the reagent blank
exceeds its determined MDL, then laboratory or reagent
contamination should be suspected. Any determined source of
contamination should be corrected and the samples reanalyzed.
10.3.2 Laboratory fortified blank (LFB) - The laboratory must
analyze at least one LFB (Sect. 7.11) with each batch of
samples. Calculate accuracy as percent recovery (Sect.
10.4.2). If the recovery of any analyte falls outside the
control limits (Sect. 10.3.3), that analyte is judged out of
control, and the source of the problem should be identified
and resolved before continuing analyses.
10.3.3 Until sufficient LFB data become available (usually a minimum
of 20 to 30 analyses), the laboratory should assess
laboratory performance against recovery limits of 85-115%.
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
fol1ows:
UPPER CONTROL LIMIT = x + 3S
LOWER CONTROL LIMIT = x - 3S
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After each five to ten new recovery measurements, new control
limits should be calculated using only the most recent 20 to
30 data points.
10.4 ASSESSING ANALYTE RECOVERY - LABORATORY FORTIFIED SAMPLE MATRIX
10.4.1 The laboratory must add a known amount of each analyte to a
minimum of 10% of the routine samples or one sample per
sample set, whichever is greater. Ideally for water samples,
the analyte concentration should be the same as that used in
the LFB (Sect. 10.3.2). This is also recommended for solid
samples, however, the concentration added should be expressed
as mg/kg and calculated by multiplying the values given in
Sect. 7.11 by the factor 100. Over time, samples from all
routine sample sources should be fortified.
10.4.2 Calculate the percent recovery for each analyte, corrected
for background concentrations measured in the unfortified
sample, and compare these values to the control limits
established in Sect. 10,3.3 for the analyses of LFBs.
Recovery calculations are not required if the concentration
added is less than 10% of the sample background concen-
tration. Percent recovery may be calculated in units
appropriate to the matrix, using the following equation:
R = Cs " C x 100
s
where, R = percent recovery.
Cs = fortified sample concentration.
C = sample background concentration.
s = concentration equivalent of analyte added to
sample.
10.4.3 If recovery of any analyte falls outside the designated range
and laboratory performance for that analyte is shown to be in
control (Sect. 10.3), 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 matrix effects and analysis by method of standard
addition (Sect. 9.8) should be considered.
11. PROCEDURE
11.1 AQUEOUS SAMPLE PREPARATION - DISSOLVED ELEMENTS
11.1.1 For the determination of dissolved elements in ground and
surface waters, take a 100 mL (± 1 mL) aliquot of the
filtered acid preserved sample, add 2 mL of (1+1) nitric acid
61
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and 1 ml (1+1) hydrochloric acid. The sample is now ready
for analysis. 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 Sect. 11.2.1 prior to analysis.
11.2 AQUEOUS SAMPLE PREPARATION - TOTAL RECOVERABLE ELEMENTS
11.2.1 For determination of total recoverable elements in water or
waste water, other than marine and estuarine water, take a
100 mL (± 1 mL) aliquot from a well mixed, acid preserved
sample and transfer it to a 250-mL Griffin beaker. [For
drinking water compliance monitoring certain analytes require
4X preconcentration prior to analysis (Sect. 1.7)]. Add 2 mL
of (1+1) nitric acid and 1.0 mL of (1+1) hydrochloric acid.
Heat the sample.on a hot plate at 85°C until the volume has
been reduced to approximately 20 mL, ensuring that the sample
does not boil. (A spare beaker containing 20 mL of water can
be used as a gauge.)
NOTE: For proper heating adjust the temperature control of
the hot plate such that an uncovered beaker containing
50 mL of water located in the center of the hot plate can
be maintained at a temperature no higher than 85°C.
Evaporation time for 100 mL of sample at 85°C is
approximately 2 h with the rate of evaporation rapidly
increasing as the sample volume approaches 20 mL.
Cover the beaker with a watch glass and reflux for 30 min.
Slight boiling may occur but vigorous boiling should be
avoided. Allow to cool and quantitatively transfer to
either a 50-mL volumetric or a 50-mL class A stoppered
graduated cylinder. Dilute to volume with ASTM type I water
and mix. Centrifuge the sample or allow to stand overnight
to separate insoluble material. The sample is now ready for
analysis. Because the effects of various matrices on the
stability of diluted samples cannot be characterized, samples
should be analyzed as soon as possible after preparation.
11.2.2 For determination of total recoverable elements in marine and
estuarine water, take a 100 mL aliquot from a well mixed,
acid preserved sample and transfer to a 250-mL Griffin
beaker. Add 2 mL of (1+1) nitric acid and heat on a hot plate
at 85°C until the volume has been reduced to approximately
25 mL, ensuring that the sample does not boil. (See NOTE in
Sect. 11.2.1). Cover the beaker with a watch glass and
reflux for 30 min. Slight boiling may occur but vigorous
boiling should be avoided. Allow to cool and dilute to 100
mL with ASTM type I water. Centrifuge the sample or allow to
62
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stand overnight to separate insoluble material. The sample
is now ready for analysis by the method of standard addition
(Sect. 9.8). Because the effects of various matrices on the
stability of diluted samples cannot be characterized, samples
should be analyzed as soon as possible after preparation.
11.3 SOLID SAMPLE PREPARATION - TOTAL RECOVERABLE ELEMENTS
11.3.1 For determination of total recoverable elements in solid
samples (sludge, soils, and sediments), mix the sample
thoroughly to achieve homogeneity and weigh accurately a 1.0
± 0.01 g portion of the sample. Transfer to a 250-mL
Phillips beaker. Add 4 mL (1+1) nitric acid and 10 mL (1+4)
hydrochloric acid. Cover with a watch glass. Heat the
sample on a hot plate and gently reflux for 30 min. Very
slight boiling may occur, however, vigorous boiling must be
avoided to prevent the loss of the HC1-H20 azeotrope.
NOTE: For proper heating adjust the temperature control
of the hot plate such that an uncovered Griffen beaker
containing 50 mL of water located in the center of the hot
plate can be maintained at a temperature of approximately
but no higher than 85°C.
Allow the sample to cool and quantitatively transfer to 100-
mL volumetric flask. Dilute to volume with ASTM type I water
and mix. Centrifuge the sample or allow to stand overnight
to separate insoluble material. The sample is now ready for
analysis. Because the effects of various matrices on the
stability of diluted samples cannot be characterized, samples
should be analyzed as soon as possible after preparation.
NOTE: Determine the percent solids in the sample for
calculating and reporting data on a dry weight basis. To
determine the dry weight, transfer a separate, uniform 1 g
aliquot to an evaporating dish and dry to a constant
weight at 103-1056C.
11.4 SAMPLE ANALYSIS
11.4.1 Analyze the samples by the procedural routine described in
Sects. 9.5, 9.6 and 9.7. If method of standard additions are
required follow the instructions given in Sect. 9.8. Samples
having concentrations higher than the established linear
dynamic range (LDR) should be diluted into range and
reanalyzed. The sample may first be analyzed for trace
analytes providing the elements in high concentration do not
cause a severe matrix effect and any interelement spectral
interference or shift in background intensity can be properly
corrected.
63
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11.4.2 For drinking water compliance monitoring, if the
concentration of a primary contaminant is determined to be
90% of its MCL or above and the combined Mg and Ca
concentration equals 500 mg/L, the sample should be analyzed
by the standard addition technique (Sect. 9.8).
12. CALCULATIONS
12.1 Sample data should be reported in units of mg/L for aqueous samples
and mg/kg dry weight for solid samples. Do not report element
concentrations below the determined MDL.
12.2 For aqueous samples prepared by total recoverable procedure (Sect.
11.2.1), multiply solution concentrations by the dilution factor
0.5. Round the data to the thousandth place and report the data in
mg/L up to three significant figures.
12.3 For estuarine and marine water samples prepared by total recoverable
procedure (Sect. 11.2.2), read the concentration directly from the
instrument and calculate the sample concentration by the procedure
described in Sect. 9.8. Round the data to the thousandth place and
report the data in mg/L up to three significant figures.
12.4 For solid samples prepared by total recoverable procedure (Sect.
11.3) round the solution concentrations (fig/mi, in the analysis
solution) to the thousandth place and multiply by the dilution
factor 100. Report the data to a 0.1 mg/kg up to three significant
figures taking into account the percent solids as noted in Sect.
11.3 when the data are reported on a dry weight basis.
12.5 If additional dilutions were performed or if a drinking water sample
was preconcentrated 4x for analysis, the appropriate factor must be
applied to sample values.
12.6 The QC data obtained during sample analyses provide an indication of
the quality of the sample data and should be provided with the
sample results.
13. PRECISION AND ACCURACY
13.1 Listed in Table 2 are MDLs determined using the procedure described
in Sect. 10.2.2. The MDLs were determined in the reagent blank
matrix (best case situation) following sample preparation given in
Sect. 11.2.1. Teflon beakers were used to avoid boron and silica
contamination from glassware with the final dilution to 50 mL
completed in polypropylene centrifuged tubes.
13.2 Data obtained from single laboratory method testing are summarized
in Table 5 for five types of water samples consisting of drinking
water, surface water, ground water, and two wastewater effluents.
Samples were prepared using the procedure described in Sect. 11.2.1.
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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 5. 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 6 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 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.
13.4 Data obtained from single laboratory method testing when using the
procedure given in Sect. 11.2.1 but utilizing the 4X preconcen-
tration step prior to analysis as required for the determination of
certain drinking water contaminants are summarized in Table 7.
Seven replicate aliquots of Cincinnati, Ohio, tapwater were prepared
and analyzed to determine background concentrations. In addition,
two more sets of seven replicates each were fortified at different
levels of concentration with an attempt to bracket or match either
current or proposed Maximum Contaminant Level concentrations. For
each method analyte, the sample background concentration,
concentration added, mean percent recovery of the fortified
addition, and relative standard deviation of the mean recovery are
listed in Table 7. All aliquots were processed in Teflon beakers
and diluted to volume in polypropylene centrifuged tubes. The
sample analyte less than values indicate 4X MDLs. The 4X MDL values
for the analytes: Al, B, Ba, Mn, Sr and Zn are 0.01, 0.002, 0.0003,
0.0002, 0.0002 and 0.001 mg/L, respectively.
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14. REFERENCES
1.
4.
5.
8.
10,
11.
12.
13.
14.
Larson, G.F., V.A. Fassel, R.K. Winge and R.N. Kniseley, "Ultratrace
Analysis by Optical Emission Spectroscopy: The Stray Light Problem "
Applied Spectroscopy 30:384 (1976).
Botto, R. I., "Quality Assurance in Operating a Multielement ICP
Emission Spectrometer," Spectrochem. Act. 398:95 (1984).
Botto, R.I., "Long-term Stability of Spectral Interference
Calibrations for Inductively Coupled Plasma Atomic Emission
Spectrometry," Analytical Chemistry, 54:1654 (1982).,
Code of Federal Regulations 40, Ch. 1, Pt. 136 Appendix B.
Handbook for Analytical Quality Control in Water and Wastewater
Laboratories, EPA-600/4-79-019.
"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.
"OSHA Safety and Health Standards, General Industry," (29 CFR
1910), Occupational Safety and Health Administration, OSHA 2206,
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"Proposed OSHA Safety and Health Standards, Laboratories,"
Occupational Safety and Health Administration, Federal Register
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Annual Book of ASTM Standards, Volume 11.01.
Wallace, G.F., "Some Factors Affecting the Performance of an ICP
Sample Introduction System," Atomic Spectroscopy, Vol. 4, pp. 188-
192 (1983).
Koirtyohann, S.R., J.S. Jones and D.A. Yates, "Nomenclature System
for the Low-Power Argon Inductively Coupled Plasma," Analytical
Chemistry, 52:1965 (1980).
Winefordner, J.D., "Trace Analysis: Spectroscopic Methods for
Elements," Chemical Analysis, Vol. 46, pp. 41-42.
ADDITIONAL BIBLIOGRAPHY
14.1 Winge, R.K., V.A. Fassel, V.J. Peterson and M.A. Floyd,
"Inductively Coupled Plasma-Atomic Emission Spectroscopy: An
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Atlas of spectral Information," Physical Science Data 20,
Elsevier Science, 1985.
14.2 Winge, R.K., V.A. Fassel, R.N. Kniseley, F. DeKalb and W.J.
Haas, Jr., "Determination of Trace Elements in Soft, Hard and
Saline Waters by Inductively Coupled Plasma, Multi-Element
Atomic Emission spectroscopic (ICP-AES) Technique,"
Spectrochemica Acta, 328:327 (1977).
14.3 Garbarino, J.R. and Taylor, H.E., "An Inductively-Coupled
Plasma Atomic Emission Spectrometric Method for Routine Water
Quality Testing," Applied Spectroscopy 33, No. 3(1979).
14.4 Method 200.7, Inductively Coupled Plasma-Atomic Emission
Spectrometer Method for Trace Element Analysis of Water and
Wastes. Revision 1.0, July, 1979, U.S. Environmental
Protection Agency, Office of Research and Development,
Environmental Monitoring and Support Laboratory, Cincinnati,
Ohio 45268.
14.5 Appendix to Method 200.7, Inductively Coupled Plasma Atomic
Analysis of Drinking Water, Revision 1.3, March, 1987, U.S.
Environmental Protection Agency, Office of Research and
Development, Environmental Monitoring Systems Laboratory,
Cincinnati, Ohio 45268.
67
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TABLE 1. RECOMMENDED WAVELENGTHS WITH LOCATIONS FOR BACKGROUND CORRECTION AND
ESTIMATED INSTRUMENT DETECTION LIMITS (IDL)
Analyte
Wavelength, nm1
Location for
Bkgd. Correction
Estimated IDLs
mg/L<2>
Ag
Al
As
B
Ba
Be
Ca
Cd
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Ho
Na
Ni
P
Pb
Sb
Se
Si02
Sn
Sr
Tl
V
Zn
328.068
308.215
193.696
249.678x2
493.409
313.042
315.887
226.502
228.616
205.552x2
324.754
259.940
194.227x2
766.491
670.784
279.079
257.610
203.844
588.995
231.604x2
214.914x2
220.353
206.833
196.090
251.611
189.980x2
421.552
190.864
292.402
213.856x2
+0.070 nm
+0.070 nm
+0.070 nm
+0.035 nm
-0.064 nm
-0.064 nm
+0.070 nm
+0.070 nm
-0.064 nm
-0.032 nm
-0.064 nm
+0.070 nm
-0.032 nm
-0.064 nm
+0.070 nm
-0.064 nm
+0.070 nm
-0.064 nm
+0.070 nm
+0.035 nm
+0.035 nm
-0.064 nm
+0.070 nm
+0.070 nm
-0.064 nm
-0.032 nm
+0.070 nm
-0.064 nm
+0.070 nm
+0.035 nm
0.005
0.05
0.03
0.006
0.001
0.0007
0.02
0.002
0.007
0.007
0.003
0.007
0.02
0.7
0.005
0.03
0.0008
0.02
0.03
0.009
0.09
0.03
0.03
0.08
0.02
0.02
0.0006
0.03
0.009
0.002
(1) Wavelength x 2 indicates wavelength is read in second order.
(2) The IDLs were estimated from three times the standard deviation of 10 replicate
measurements of the calibration blank.* .The calculated IDL was rounded upward and
reported to a single digit.
68
-------
TABLE 2. TOTAL RECOVERABLE METHOD DETECTION LIMITS (MDL)
r~
Anal
Ag
Al
As
B
Ba
Be
Ca
Cd
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
|Na
FNi
P
Pb
Sb
Se
MDLs
vte Aaueous. ma/L<1)
0.002
0.02
0.008
0.003
0.001
0.0003
0.01
0.001
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
Solids. ma/Kq<2)
0.3
3
2
-
0.2
0.1
2
0.2
0.4
0.8
0.5
6
2
60
2
3
0.2
1
20
1
12
2
2
5
Si02 0.02
Sn
Sr
Tl
V
Zn
(1)
(2)
0.007
0.0003
0.02
0.003
0.002
MDL concentrations are computed for original
preconcentration during preparation. Samples
diluted in 50-mL plastic centrifuge tubes.
Based on aqueous solution determination.
2
0.1
3
1
0.3
matrix with allowance for 2x sample
were processed in Teflon and
Boron not reported because of glassware contamination.
Silica not determined in solid samples. •
Elevated value due to fume hood contamination.
69
-------
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TABLE 4. 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
72
-------
PB-CU ICP-AES EMISSION PROFILE
32
30
28
26
24
22
20
18
16
14h
Net Emission Intensity Counts /Thousands
12
475 525 575 625 675 725 775 825
Nebulizer Argon Flow Rate - mL/min
Copper
Lead
FIGURE 1
73
-------
TABLE 5. PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES
TAP WATER
SAMPLE LOW
CONC SPIKE
ANALYTE mg/L mg/L
AVERAGE
RECOVERY
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
Si02
Sn
Sr
Tl
V
Zn
<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
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
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
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
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
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
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.
74
-------
TABLE 5. PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont'd.)
POND WATER
SAMPLE LOW
CONC SPIKE
ANALYTE mg/L mg/L
AVERAGE
RECOVERY
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
Si02
Sn
Sr
Tl
V
Zn
<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
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
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
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
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
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
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
S(R)
RPD
<
*
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.
75
-------
TABLE 5. PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont'd.)
WELL WATER
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
Ho
Na
Ni
P
Pb
Sb
Se
SiOe
Sn
Sr
Tl
V
Zn
<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
*
2.1
10.1
1.9
0.7
0.0
0.0
2.1
0.0
1.1
20.0
0.4
1.4
8.5
3.6
9.5
0.3
0.4
4.7
0.8
4.4
1.9
16.1
8.2
1.0
2.8
8.2
2.7
1.1
0.0
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
0.2
1.1
0.4
0.8
0.9
0.0
4.1
0.0
0.4
0.4
0.5
1.4
1.2
1.2
1.0
1.6
*
0.2
3.1
0.2
3.4
0.2
1.4
1.1
0.8
0.2
1.7
1.1
0.4
2.5
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
S(R)
RPD
<
*
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.
76
-------
TABLE 5. PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont'd.)
SAMPLE LOW
CONC SPIKE
ANALYTE mg/L mg/L
S
Al
As
B
Ba
Be
Ca
Cd
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
P
Pb
Sb
Se
f* * f\
Si02
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
Relative percent di
AVERAGE
RECOVERY
D (®/ \
\ /
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
fference b<
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
stween dii
^^-~ — — - —
HIGH
SPIKE
RPD mg/L
3.6 0.2
0.9 0.2
6.1 0.2
9.5 0.4
1.7 1 0.2
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
0.1
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
•
nlirato cn-ilca Ho
===^=
AVERAGE
RECOVERY
:
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
•h a v»m -i Y\ i -t- •! i
" - - -— —
S(R)
-
0.1
12.4
2 1
t» * J.
13.1
1.6
0.4
3.7
0 4
w • ~
0 4
v * ~
2.4
3.0
7.0
0 5
V • V
0.6
0.8
1 i
± • J.
1.9
1.3
*
0.8
*
1.3
1.1
2.6
1.1
1.0
1 6
1 • \J
0 0
V * v
0 2
V • f—
1.0
•Mrt t+
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
• ---_, — __ vvv.,Wx*n N**4|^ii^,
-------
TABLE 5. PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont'd.)
INDUSTRIAL EFFLUENT
ANALYTE
Ag
• ij3
Al
As
B
Ba
Be
Ca
Cd
Co
Cr
Cu
Fe
Hg
* *3
K
Li
Mg
* *3
Mn
Mo
Na
Ni
p
Pb
Sb
Se
Si02
Sn
Sr
Tl
V
Zn
SAMPLE LOW
CONC SPIKE
mg/L mg/L
<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
AVERAGE
RECOVERY
R(%)
88
88
82
162
86
94
*
85
93
*
93
88
87
101
103
87
*
*
*
98
105
80
*
106
99
87
*
87
90
89
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
S(R)
RPD
<
*
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.
78
-------
TABLE 6. PRECISION AND RECOVERY DATA IN SOLID MATRICES
EPA HAZARDOUS SOIL #884
ANALYTE
SAMPLE LOW+ AVERAGE
CONC SPIKE RECOVERY
pig/kg mg/kg R(%) S(R)
RPD
HIGH"" AVERAGE
SPIKE RECOVERY
mg/kg 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
1.1
5080
5.7
20.4
HI
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
98
*
95
93
98
97
-
93
96
87
110
—
92
121
113
*
*
88
102
. 100
106
88
83
79
91
84
92
104
103
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
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
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
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
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
S(R)
RPD
<
*
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 spiked.
Equivalent
79
-------
TABLE 6. PRECISION AND RECOVERY DATA IN SOLID MATRICES (Cont.)
EPA ELECTROPLATING SLUDGE #286
SAMPLE LOW"*"
CONC SPIKE
ANALYTE mg/kg mg/kg
AVERAGE
RECOVERY
S(R)
RPD
HIGH"*" AVERAGE
SPIKE RECOVERY
mg/kg 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
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
96
*
94
113
0
96
-
98
93
*
*
-
90
75
101
110
*
92
*
*
*
*
76
86
87
90
89
95
*
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
*
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
93.2
*
97
98
0
100.68
-
96
93
*
94
-
97
94
106
108
91
92
*
88
114
*
75
103
92
93
92
96
*
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
*
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
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.
Not spiked.
+ Equivalent
80
-------
TABLE 6. PRECISION AND RECOVERY DATA IN SOLID MATRICES (Cont.)
NBS 1645 RIVER SEDIMENT
ANALYTE
SAMPLE
CONC
LOW"1"
SPIKE
mg/kg
AVERAGE
RECOVERY
S(R)
RPD
HIGH"1" AVERAGE
SPIKE RECOVERY
rag/kg 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
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
92
*
89
116
95
101
_
100
98
*
115
_
99
98
101
*
*
97
92
94
102
*
86
103
*
91
90
89
*
Standard deviation of percent
Relative percent difference b'«
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
*
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
96
*
97
95
98
103
101
98
*
102
96
106
108
93
97
98
97
100
100
103
88
98
101
96
95
98
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
*
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.
Jtween duplicate soike determinations.
f ..— — P . . w • -v • . v w Mwv*ii^i_|| U 14LS I I V* IA VX* *J LS I IX Vi V4CUCI III I I I CL Lr
Sample concentration below established method detection limit.
Spike concentration <10% of sample background concentration.
Not spiked.
Equivalent
81
-------
TABLE 7. DRINKING WATER 4X PRECONCENTRATION PRECISION AND RECOVERY DATA (1)
SAMPLE LOW
CONC SPIKE
ANALYTE mg/L mg/L
AVERAGE
RECOVERY
RSD(%)
HIGH AVERAGE
SPIKE RECOVERY
mg/L R(%) RSD(%)
Ag
AT
As
B
Ba
Be
Ca
Cd
Cr
Cu
Fe
Hg
K
Mg
Hn
Ho
Na
Ni
Pb
Sb
Se
Sr
Tl
V
Zn
<0.001
0.102
<0.004
0.022
0.037
<0.0002
32.6
<0.0006
<0.002
<0.001
<0.02
<0.003
2.09
7.49
0.002
<0.003
8.21
<0.002
<0.005
<0.004
<0.01
0.160
<0.008
<0.002
0.003
0.025
0.05
0.02
0.02
0.5
0.001
-
0.005
0.05
0.5
0.1
0.01
-
-
0.005
0.01
-
0.01
0.01
0.01
0.05
0.1
0.02
0.01
0.02
95
95
101
100
101
100
-
100
99
99
114
84
-
-
100
103
-
112
105
106
107
94
98
100
101
0.5
1.6
10.9
1.2
0.7
0.0
1.9
2.4
1.0
0.7
5.4
7.1
2.2
2.0
1.4
5.3
1.9
1.9
11.4
7.5
8.8
0.3
8.6
3.1
1.8
0.12
0.2
0.08
0.08
2.0
0.004
-
0.02
0.2
2.0
0.4
0.04
-
-
0.02
0.04
-
0.04
0.04
0.04
0.2
0.4
0.08
0.04
0.08
95
104
98
96
98
100
-
95
96
96
102
94
-
-
110
102
-
103
108
99
96
102
100
100
95
4.6
5.2
3.6
5.1
4.0
5.0
-
3.8
3.9
3.3
5.0
6.6
-
-
4.8
4.6
-
5.6
4.4
9.1
5.6
4.7
4.4
5.7
5.0
82
-------
METHOD 200.8
DETERMINATION OF TRACE ELEMENTS IN WATERS AND WASTES
BY INDUCTIVELY COUPLED PLASMA - MASS SPECTROMETRY
Stephen E. Long
Technology Applications,
and
Inc.
Theodore D. Martin
Inorganic Chemistry Branch
Chemistry Research Division
Revision 4.4
April 1991
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
83
-------
METHOD 200.8
DETERMINATION OF TRACE ELEMENTS IN WATERS AND WASTES
BY INDUCTIVELY COUPLED PLASMA - MASS SPECTROMETRY
1. 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
solid waste samples.
1.2 Dissolved elements are determined after suitable filtration and acid
preservation. Acid digestion procedures are required prior to
determination of total recoverable elements. In order to reduce
potential interferences, dissolved solids should not exceed
0.2% (w/v) (Sect. 4.1.4).
1.3 This method is applicable to the following elements:
Element
Aluminum (Al)
Antimony (Sb)
Arsenic (As)
Barium (Ba)
Beryllium (Be)
Cadmium (Cd)
Chromium (Cr)
Cobalt (Co)
Copper (Cu)
Lead (Pb)
Manganese (Mn)
Molybdenum (Mo)
Nickel (Ni)
Selenium (Se)
Silver (Ag)
Thallium (Tl)
Thorium (Th)
Uranium (U)
Vanadium (V)
Zinc (Zn)
Chemical Abstract Services
Registry Numbers (CASRN)
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
7439-98-7
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)
84
-------
and linear working ranges will be dependent on the sample matrix,
instrumentation and selected operating conditions.
1.4 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.
1.5 This method should be used by analysts experienced in the use of
inductively coupled plasma mass spectrometry (ICP-MS), the
interpretation of spectral and matrix interferences and procedures
for their correction. A minimum of six months experience with
commercial instrumentation is recommended.
2. SUMMARY OF METHOD
2.1 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 registered by a con-
tinuous dynode 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. Instrumen-
tal drift as well as suppressions or enhancements of instrument
response caused by the sample matrix must be corrected for by the
use of internal standardization.
3. DEFINITIONS
3.1 DISSOLVED - Material that will pass through a 0.45 fj,m membrane
filter assembly, prior to sample acidification.
3.2 TOTAL RECOVERABLE - The concentration of analyte determined on an
unfiltered sample following treatment with hot dilute mineral acid.
3.3
INSTRUMENT DETECTION LIMIT (IDL) - The concentration equivalent of
the analyte signal, which is equal to three times the standard
deviation of the blank signal at the selected analytical mass(es).
3.4 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.
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3.5 LINEAR DYNAMIC RANGE (LDR) - The concentration range over which the
analytical working curve remains linear.
3.6 LABORATORY REAGENT BLANK (LRB) (preparation blank) - An aliquot of
reagent water that is treated exactly as a sample including exposure
to all labware, 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, the reagents or apparatus.
3.7 CALIBRATION BLANK - A volume of ASTM type I water acidified with the
same acid matrix as is present in the calibration standards.
3.8 INTERNAL STANDARD - Pure analyte(s) added to a solution in known
amount(s) and used to measure the relative responses of other method
analytes that are components of the same solution. The internal
standard must be an analyte that is not a sample component.
3.9 STOCK STANDARD SOLUTION - A concentrated solution containing one or
more analytes prepared in the laboratory using assayed reference
compounds or purchased from a reputable commercial source.
3.10 CALIBRATION STANDARD (CAL) - A solution prepared from the stock
standard solution(s) which is used to calibrate the instrument
response with respect to analyte concentration.
3.11 TUNING SOLUTION - A solution which is used to determine acceptable
instrument performance prior to calibration and sample analyses.
3.12 LABORATORY FORTIFIED BLANK (LFB) - An aliquot of reagent water 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 method performance is within
accepted control limits.
3.13 LABORATORY FORTIFIED SAMPLE MATRIX (LFM) - An aliquot of an
environmental sample to which known quantities of the method analy-
tes 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 concen-
trations of the analytes in the sample matrix must be determined in
a separate aliquot and the measured values in the LFM corrected for
the concentrations found.
3.14 QUALITY CONTROL SAMPLE (QCS) - A solution containing known
concentrations of method analytes which is used to fortify an
aliquot of LRB matrix. The QCS is obtained from a source external
to the laboratory and is used to check laboratory performance.
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4. 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
determined 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
molybdenum-98 (ruthenium) and selenium-82 (krypton) have
isobaric 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 condi-
tions 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 and instrument bias factors 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 identified , 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.
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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
between 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 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 recommended3 to reduce such effects.
Internal standardization may be effectively used to
compensate for many physical interference effects4. 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 concentration 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.
5. 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
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5.2
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
available to all personnel involved in the chemical analysis.
Analytical plasma sources emit radiofrequency radiation in addition
to intense UV radiation. Suitable precautions should be taken to
protect personnel from such hazards.
6. APPARATUS AND EQUIPMENT
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
extended dynamic range detection system.
6.1.2 Argon gas supply (high-purity grade, 99.99%).
6.1.3 A variable-speed peristaltic pump is required for solution
delivery to the nebulizer.
6.1.4 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).
6.1.5 Operating conditions - Because of the diversity of instrument
hardware, no detailed instrument operating conditions are
provided. 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. Instrument
operating conditions which were used to generate precision
and recovery data for this method (Sect. 13) are included in
Table 6.
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
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 LABWARE - For the determination of trace levels of elements,
contamination and loss are of prime consideration. Potential
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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 con-
centrations through adsorption processes. All reuseable labware
(glass, quartz, polyethylene, Teflon, etc.) including the sample
container should be cleaned prior to use. Labware may be soaked
overnight and thoroughly washed with laboratory-grade detergent and
water, rinsed with water, and soaked for four hours in a mixture of
dilute nitric and hydrochloric acid (1+2+9), followed by rinsing
with water, ASTM type I water and oven drying.
NOTE: Chromic acid must not be used for cleaning glassware.
6.2.1 Glassware - Volumetric flasks, graduated cylinders, funnels
and centrifuge tubes.
6.2.2 Assorted calibrated pipettes.
6.2.3 Conical Phillips beakers, 250-mL with 50-mm watch glasses.
Griffin beakers, 250-mL with 75-mm watch glasses.
6.2.4 Storage bottles - Narrow mouth bottles, Teflon FEP
(fluorinated ethylene propylene) with Tefzel ETFE (ethylene
tetrafluorethylene) screw closure, 125-mL and 250-mL
capacities.
6.3 SAMPLE PROCESSING EQUIPMENT
6.3.1 Air Displacement Pipetter - Digital pipet system capable of
delivering volumes from 10 to 2500 /zL with an assortment of
high quality disposable pipet tips.
6.3.2 Balance - Analytical, capable of accurately weighing to
0.1 mg.
6.3.3 Hot Plate - (Corning PC100 or equivalent).
6.3.4 Centrifuge - Steel cabinet with guard bowl, electric timer
and brake.
6.3.5 Drying Oven - Gravity convection oven with thermostat!c
control capable of maintaining 105°C ± 5°C.
7. REAGENTS AND CONSUMABLE MATERIALS
7.1 Reagents may contain elemental impurities that might affect the
integrity of analytical data. Owing to the high sensitivity of ICP-
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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
ASTM type I water and dilute to 1 L.
7.1.3 Nitric acid (1+9) - Add 100 ml cone, nitric acid to 400 ml of
ASTM type I 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 ASTM type I water and dilute to 1 L.
7.1.6 Hydrochloric acid (1+4) - Add 200 mL cone, hydrochloric acid
to 400 ml of ASTM type I 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).
7.2 WATER - For all sample preparation and dilutions, ASTM type I water
(ASTM D1193) is required. Suitable water may be prepared by passing
distilled water through a mixed bed of anion and cation exchange
resins.
7.3 STANDARD STOCK SOLUTIONS - 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. (CAUTION: Many metal salts
are extremely toxic if inhaled or swallowed. Wash hands thoroughly
after handling). Stock solutions should be stored in Teflon
bottles. The following procedures may be used for preparing stan-
dard 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.
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7.3.1 Aluminum solution, stock 1 ml = 1000 jug 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 ASTM type I water. Heat
until the volume is reduced to 2 mL. Cool and dilute to
100 mL with ASTM type I water.
7.3.2 Antimony solution, stock 1 mL = 1000 jug 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 ASTM type I water and 0.15 g tartaric acid. Warm the
solution to dissolve the white precipitate. Cool and dilute
to 100 mL with ASTM type I water.
7.3.3 Arsenic solution, stock 1 mL = 1000 /zg As: Dissolve 0.1320 g
As203 in a mixture of 50 mL ASTM type I 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 ASTM type I water.
7.3.4 Barium solution, stock 1 mL = 1000 p,g Ba: Dissolve 0.1437 g
BaC03 in a solution mixture of 10 mL ASTM type I water and
2 mL cone, nitric acid. Heat and stir to effect solution and
degassing. Dilute to 100 mL with ASTM type I water.
7.3.5
7.3.6
7.3.7
Beryllium solution, stock 1 mL = 1000 ng Be: Dissolve
1.965 g BeS04.4HpO (DO NOT DRY) in 50 mL ASTM Type I water.
Add 1 mL cone, nitric acid. Dilute to 100 mL with ASTM type
I water.
Bismuth solution, stock 1 mL = 1000 p,g Bi: Dissolve 0.1115 g
Bi203 in 5 mL cone, nitric acid. Heat to effect solution.
Cool and dilute to 100 mL with ASTM type I water.
Cadmium solution, stock 1 mL = 1000 /xg 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 ASTM type I water.
7.3.8 Chromium solution, stock 1 mL = 1000 ng Cr: Dissolve
0.1923 g Cr03 in a solution mixture of 10 mL ASTM type I
water and 1 mL cone, nitric acid. Dilute to 100 mL with ASTM
type I water.
7.3.9 Cobalt solution, stock 1 mL = 1000 ;ug Co: Pickle cobalt
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 ASTM type I water.
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7.3.10 Copper solution, stock 1 ml = 1000 /zg 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 ASTM type I water.
7.3.11 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 ASTM type I water.
7.3.12 Lead solution, stock 1 ml = 1000 jug Pb: Dissolve 0.1599 g
PbN03 in 5 mL (1+1) nitric acid. Dilute to 100 ml with ASTM
type I water.
7.3.13 Magnesium solution, stock 1 ml = 1000 ng Mg: Dissolve
0.1658 g MgO in 10 ml (1+1) nitric acid, heating to effect
solution. Cool and dilute to 100 ml with ASTM type I water.
7.3.14
7.3.15
7.3.16
7.3.17
Manganese solution, stock 1 ml = 1000 jug Mn: Pickle
manganese flake 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 ASTM type I
water.
Molybdenum solution, stock 1 ml = 1000 /xg Mo: Dissolve
0.1500 g Mo03 in a solution mixture of 10 ml ASTM type I
water and 1 ml cone, ammonium hydroxide., heating to effect
solution. Cool and dilute to 100 ml with ASTM type I water.
Nickel solution, stock 1 ml = 1000 /jg Ni: Dissolve 0.100 g
nickel powder in 5 ml cone, nitric acid, heating to effect
solution. Cool and dilute to 100 ml with ASTM type I water.
Scandium solution, stock 1 ml = 1000 jug Sc: Dissolve
0.1534 g Sc203 in 5 ml (1+1) nitric acid, heating to effect
solution. Cool and dilute to 100 ml with ASTM type I water.
7.3.18 Selenium solution, stock 1 ml = 1000 jug Se: Dissolve
0.1405 g Se02 in 20 ml ASTM type I water. Dilute to 100 ml
with ASTM type I water.
7.3.19 Silver solution, stock 1 ml = 1000 ng 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 ASTM type I water.
Store in dark container.
7.3.20 Terbium solution, stock 1 ml = 1000 jug Tb: Dissolve 0.1176 g
Tb,07 in 5 ml cone, nitric acid, heating to effect solution.
Cool and dilute to 100 ml with ASTM type I water.
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7.4
7.3.21 Thallium solution, stock 1 mL = 1000 p,g Tl: Dissolve
0.1303 g T1NO, in a solution mixture of 10 mL ASTM type I
water and 1 ml cone, nitric acid. Dilute to 100 ml with ASTM
type I water.
7.3.22 Thorium solution, stock 1 ml = 1000 /ig Th: Dissolve 0.2380 g
Th(N03)4.4H,0 (DO NOT DRY) in 20 ml ASTM type I water.
Dilute to 100 ml with ASTM type I water.
7.3.23 Uranium solution, stock 1 ml = 1000 jug U: Dissolve 0.2110 g
UO§(N03)2.6H,0 (DO NOT DRY) in 20 ml ASTM type I water and
dilute to 100 mL with ASTM type I water.
7.3.24 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 ASTM type I water.
7.3.25 Yttrium solution, stock 1 mL = 1000 jug Y: Dissolve 0.1270 g
Y20, in 5 mL (1+1) nitric acid, heating to effect solution.
Cool and dilute to 100 mL with ASTM type I water.
7.3.26 Zinc solution, stock 1 mL = 1000 jug 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 ASTM type I water.
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
Aluminum
Antimony
Arsenic
Beryl 1i urn
Cadmium
Chromium
Cobalt
Copper
Lead
Manganese
Molybdenum
Nickel
Selenium
Thallium
Thorium
Uranium
Vanadium
Zinc
Standard Solution B
Barium
Silver
Multielement stock standard solutions A and B (1 mL = 10 /Ltg) may be
prepared by diluting 1 mL of each single element stock in the
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combination list to 100 ml with ASTM type I water containing 1%
(v/v) nitric acid.
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
solutions A and B to levels appropriate to the operating
range of the instrument using ASTM type I 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. Concentrations of 200 jug/L are
suggested. If the direct addition procedure is being used
(Method A, Sect. 9.2), add internal standards (Sect. 7.5) to
the calibration standards and store in Teflon bottles.
Calibration standards should be verified initially using a
quality control sample (Sect. 7.8).
7.5 INTERNAL STANDARDS STOCK SOLUTION, 1 mL = 100 pg. Dilute 10 mL of
scandium, yttrium, indium, terbium and bismuth stock standards
(Sect. 7.3) to 100 mL with ASTM type I water, and store in a Teflon
bottle. Use this solution concentrate for addition to blanks,
calibration standards 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. 9.2). a
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 ASTM
type I water. If the direct addition procedure (Method A,
Sect. 9.2), 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 entire sample
digestion and preparation scheme. If the direct addition
procedure (Method A, Sect. 9.2) 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 ASTM type I
water.
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
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100 ng/L of each element.
solution.
Internal standards are not added to this
7.8
7.9
QUALITY CONTROL SAMPLE (QCS) - The QCS should be obtained from a
source outside the laboratory. Dilute an appropriate aliquot of
analytes (concentrations not to exceed 1000 jug/L), in 1% (v/v)
nitric acid. If the direct addition procedure (Method A, Sect. 9.2)
is being used, add internal standards after dilution, mix and store
in a Teflon bottle.
LABORATORY FORTIFIED BLANK (LFB) - To an aliquot of LRB, add
aliquots from multielement stock standards A and B (Sect. 7.4) to
produce a final concentration of 100 fj.g/1 for each analyte. The
LFB must be carried through the entire sample digestion and
preparation scheme. If the direct addition procedure (Method A,
Sect. 9.2) is being used, add internal standards to this solution
after preparation has been completed.
8. 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, acid preservation,
etc., should be performed at the time of sample collection or as
soon thereafter as practically possible.
For the determination of dissolved elements, the sample should be
filtered through a 0.45-jum membrane filter. Use a portion of the
sample to rinse the filter assembly, discard and then collect the
required volume of filtrate. Acidify the filtrate with (1+1) nitric
acid immediately following filtration to pH < 2.
For the determination of total recoverable elements in aqueous
samples, acidify with (1+1) nitric acid at the time of collection to
pH < 2 (normally, 3 mL of (1+1) nitric acid per liter of sample is
sufficient for most ambient and drinking water samples). The sample
should not be filtered prior to analysis.
NOTE: Samples that cannot be acid preserved at the time of
collection because of sampling limitations or transport
restrictions, should be acidified with nitric acid to pH < 2 upon
receipt in the laboratory. Following acidification, the sample
should be held for 16 h before withdrawing an aliquot for sample
processing.
8.4 Solid samples usually require no preservation prior to analysis
other than storage at 4°C.
8.2
8.3
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9. CALIBRATION AND STANDARDIZATION
9.1 CALIBRATION - Demonstration and documentation of acceptable initial
calibration is required before any samples are analyzed and is
required periodically throughout sample analysis as dictated by
results of continuing calibration checks. After initial calibration
is successful, a calibration check is required at the beginning and
end of each period during which analyses are performed, and at
requisite intervals.
9.1.1 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.
9.1.2 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%.
9.1.3 Prior to initial calibration, set up proper instrument
software routines for quantitative analysis. 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.
9.1.4 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
or a minimum of 1 min. Solutions should be aspirated for 30
sec prior to the acquisition of data to allow equilibrium to
be established.
9.2 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
97
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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. 9.2), 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. 9.2). 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. A concentration of 200 p,g/L of each internal standard
is recommended. 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.
9.3 INSTRUMENT PERFORMANCE - Check the performance of the instrument and
verify the calibration using data gathered from analyses of
calibration blanks,.calibration standards and the quality control
sample (QCS).
9.3.1 After the calibration has been established, it must be
initially verified for all analytes by analyzing the QCS
(Sect. 7.8). If measurements exceed ± 10% of the
established QCS value, the analysis should be terminated, the
source of the problem identified and corrected, the
instrument recalibrated and the calibration reverified before
continuing analyses.
9.3.2 To verify that the instrument is properly calibrated on a
continuing basis, run the calibration blank and calibration
standards as surrogate samples after every ten analyses. The
results of the analyses of the standards will indicate
whether the calibration remains valid. If the indicated
concentration of any analyte deviates from the true
concentration by more than 10%, reanalyze the standard. If
the analyte is again outside the 10% limit, the instrument
must be recalibrated and the previous ten samples reanalyzed.
The instrument responses from the calibration check may be
used for recalibration purposes. 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.
10. QUALITY CONTROL
10.1 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, fortified
blanks and samples as a continuing check on performance. The
98
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10,2
laboratory is required to maintain performance records that define
the quality of the data thus generated.
10.2 INITIAL DEMONSTRATION OF PERFORMANCE
10.2.1 The initial demonstration of performance is used to
characterize instrument performance (method detection limits
and linear calibration ranges) for analyses conducted by this
method.
.2 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
limit7. 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.
MDLs should be determined every six months or whenever a
significant change in background or instrument response is
expected (e.g., detector change).
10.2.3 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. Linear calibration ranges should be
determined every six months or whenever a significant change
in instrument response is expected (e.g., detector change).
10.3 ASSESSING LABORATORY PERFORMANCE - REAGENT AND FORTIFIED BLANKS
10.3.1 Laboratory reagent blank (LRB) - The laboratory must analyze
at least one LRB (Sect. 7.6.2) with each set of samples. LRB
data are used to assess contamination from the laboratory
environment and to characterize spectral background from the
reagents used in sample processing. If an analyte value in
the reagent blank exceeds its determined MDL, then laboratory
99
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or reagent contamination should be suspected. Any determined
source of contamination should be corrected and the samples
reanalyzed.
10.3.2 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 (Sect.
10.4.2) If the recovery of any analyte falls outside the
control limits (Sect. 10.3.3), that analyte is judged out of
control, and the source of the problem should be identified
and resolved before continuing analyses.
10.3.3 Until sufficient LFB data become available (usually a minimum
of 20 to 30 analyses), the laboratory should assess
laboratory performance against recovery limits of 85-115%.
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
After each five to ten new recovery measurements, new control
limits should be calculated using only the most recent twenty
to 30 data points.
10.4 ASSESSING ANALYTE RECOVERY - LABORATORY FORTIFIED SAMPLE MATRIX
10.4.1 The laboratory must add a known amount of analyte to a
minimum of 10% of the routine samples or one sample per
sample set, whichever is greater. Ideally for water samples,
the analyte concentration should be the same as that used in
the LFB (Sect. 10.3.2). For solid samples, the concentration
added should be 50 mg/kg equivalent (100 p.g/1 in the
analysis solution). Over time, samples from all routine
sample sources should be fortified.
10.4.2 Calculate the percent recovery for each analyte, corrected
for background concentrations measured in the unfortified
sample, and compare these values to the control limits
established in Sect. 10.3.3 for the analyses of LFBs.
Recovery calculations are not required if the concentration
of the analyte added is less than 10% of the sample
background concentration. Percent recovery may be calculated
in units appropriate to the matrix, using the following
equation:
R =
- c
x 100
100
-------
where, R = percent recovery
Cs = fortified sample concentration
C = sample background concentration
s = concentration equivalent of
fortifier added to sample.
10.4.3 If recovery of any analyte falls outside the designated range
and laboratory performance for that analyte is shown to be in
control (Sect. 10.3), the recovery problem encountered with
the fortified sample is judged to be matrix related, not
system related. The result for that analyte in the
unfortified sample must be labelled "suspect/matrix" to
inform the data user that the results are suspect due to
matrix effects.
10.5 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 should not deviate more than 60-125% of the
original response in the calibration blank. If deviations greater
than this are observed, use the following test procedure:
10.5.1 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.
10.5.2 If test (Sect. 10.5.1) is not satisfied, or if it is a blank
or calibration standard that is 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.
11. PROCEDURE
11.1 SAMPLE PREPARATION - DISSOLVED ELEMENTS
11.1.1 For determination of dissolved elements in drinking water,
ground and surface waters, take a 100 mL aliquot of the
filtered acid preserved sample, and add 1 mL of concentrated
nitric acid. If the direct addition procedure (Method A) is
being used, add internal standards and mix. The sample is
now ready for analysis. Allowance for sample dilution should
be made in the calculations.
101
-------
NOTE: If a precipitate is formed during acidification,
transport or storage, the sample aliquot must be treated
using the procedure in Sect. 11.2.1 prior to analysis.
11.2 SAMPLE PREPARATION - TOTAL RECOVERABLE ELEMENTS
11.2.1 For determination of total recoverable elements in water or
wastewater, take a 100 mL aliquot from a well mixed, acid
preserved sample containing not more than 0.25% (w/v) total
solids and transfer to a 250-mL Griffin beaker (if total
solids are greater than 0.25% reduce the size of the aliquot
by a proportionate amount). Add 1 mL of cone, nitric acid
and 0.5 mL cone, hydrochloric acid. Heat on a hot plate at
85°C until the volume has been reduced to approximately 20
mL, ensuring that the sample does not boil. A spare beaker
containing 20 mL of water can be used as a guage. (NOTE:
Adjust the temperature control of the hot plate such that an
uncovered beaker containing 50 mL of water located in the
center of the hot plate can be maintained at a temperature no
higher than 85°C. Evaporation time for 100 mL of sample at
85°C is approximately 2 h with the rate of evaporation
increasing rapidly as the sample volume approaches 20 mL).
Cover the beaker with a watch glass and reflux for 30 min.
Slight boiling may occur but vigorous boiling should be
avoided. Allow to cool and quantitatively transfer to either
a 50-mL volumetric flask or 50-mL class A stoppered graduated
cylinder. Dilute to volume with ASTM type I water and mix
Centrifuge the sample or allow to stand overnight to separate
insoluble material. Prior to analysis, pipette 20 mL into a
50-mL volumetric flask, dilute to volume with ASTM type I
water and mix. If the direct addition procedure (Method A
Sect. 9.2) is being used, add internal standards and mix.
The sample is now ready for analysis. Because the stability
of diluted samples cannot be fully characterized, all
analyses should be performed as soon as possible after the
completed preparation.
11.2.2 For determination of total recoverable elements in solid
samples (sludge, soils, and sediments), mix the sample
thoroughly to achieve homogeneity and weigh accurately a
1.0 ± 0.01 g portion of the sample. Transfer to a 250-mL
Phillips beaker. Add 4 mL (1+1) nitric acid and 10 mL (1+4)
HC1. Cover with a watch glass, and reflux the sample on a
hot plate for 30 min. Very slight boiling may occur,
however, vigorous boiling must be avoided to prevent the loss
of the HCl-HpO azeotrope. (NOTE: Adjust the temperature
control of the hot plate such that an uncovered Griffin
beaker containing 50 mL of water located in the center of the
hot plate can be maintained at a temperature of approximately
but no higher than 85°C). Allow the sample to cool, and
quantitatively transfer to a 100-mL volumetric flask. Dilute
102
-------
to volume with ASTM type I water and mix. Centrifuge the
sample or allow to stand overnight to separate insoluble
material. Prior to analysis, pipette 10 ml into a 50-mL
volumetric flask and dilute to volume with ASTM type I water.
If the direct addition procedure (Method A, Sect. 9.2) 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.
NOTE: Determine the percent solids in the sample for use in
calculations and for reporting data on a dry weight basis.
11.3 For every new or unusual matrix, it is highly recommended that a
semi-quantitative analysis be carried out to screen for high element
concentrations. 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 analyz-
ing 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.
11.4 Initiate instrument operating configuration. Tune and calibrate the
instrument for the analytes of interest (Sect. 9).
11.5 Establish instrument software run procedures for quantitative
analysis. For all sample analyses, a minimum of three replicate
integrations are required for data acquisition. Discard any
integrations which are considered to be statistical outliers and use
the average of the integrations for data reporting.
11.6 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.
11.7 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. Samples should be aspirated for 30 sec prior
to the collection of data.
11.8 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
103
-------
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. CALCULATIONS
12.1 Elemental equations recommended for sample data calculations are
listed in Table 5. Sample data should be reported in units of
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 Reported values should be calibration blank subtracted. For aqueous
samples prepared by total recoverable procedure (Sect. 11.2.1)
multiply solution concentrations by the dilution factor 1.25. For
solid samples prepared by total recoverable procedure (Sect.
11.2.2), multiply solution concentrations (/ig/L in the analysis
solution) by the dilution factor 0.5. If additional dilutions were
made to any samples, the appropriate factor should be applied to the
calculated sample concentrations.
12.4 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.
12.5 If 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 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.
12.6 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.
104
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13. PRECISION AND ACCURACY
13.1 Instrument operating conditions used for single laboratory testing
of the method are summarized in Table 6. Total recoverable MDLs
determined using the procedure described in Sect. 10.2.2, are listed
in Table 7.
13.2 Data obtained from single laboratory testing of the method are
summarized in Table 8 for five water samples representing drinking
water, surface water, ground water and waste effluent. Samples were
prepared using the procedure described in Sect. 11.2.1. 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
Tables.
13.3 Data obtained from single laboratory testing of the method are
summarized in Table 9 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. 11.2.2. 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.
14. REFERENCES
1. A. L. Gray and A. R. Date, Analyst 108 1033 (1983).
2. R. S. Houk et al. Anal Chetn. 52 2283 (1980).
3. R. S. Houk, Anal. Chem. 58 97A (1986).
4. J. J. Thompson and R. S. Houk, Appl. Spec. 41 801 (1987).
5. "OSHA Safety and Health Standards, General Industry," (29 CFR 1910),
Occupational Safety and Health Administration, OSHA 2206, revised
January 1976.
6. "Proposed OSHA Safety and Health Standards, Laboratories,"
Occupational Safety and Health Administration, Federal
Register, July 24, 1986.
7. Code of Federal Regulations 40, Ch. 1, Pt. 136 Appendix B.
105
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TABLE 1: ESTIMATED INSTRUMENT DETECTION LIMITS
ELEMENT
RECOMMENDED
ANALYTICAL MASS
ESTIMATED IDL
(M9/L)
Aluminum
Antimony
Arsenic
Barium
Beryl 1i urn
Cadmium
Chromium
Cobalt
Copper
Lead
Manganese
Molybdenum
Nickel
Selenium
Silver
Thallium
Thorium
Uranium
Vanadium
Zinc
27
121
75
137
9
111
52
59
63
206.207,208
55
98
60
82
107
205
232
238
51
66
0.05
0.08
0.9
0.5
0.
0.
0.07
0.03
0.03
0.08
0.1
0.1
0.2
5
0.05
0.09
0.03
0.02
0.02
0.2
Instrument detection limits (3a) 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.
106
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TABLE 2: COMMON MOLECULAR ION INTERFERENCES IN ICP-MS
BACKGROUND MOLECULAR IONS
Molecular Ion
NH*
OH+
OH2+
C2+
CN+
C0+
N2*
N2H*
N0+
NOH+
°2+
02H+
36ArH+
38ArH+
40ArH+
C02*
C02H+
ArC^.ArO*
ArN+
ArNH+
ArO+
ArOH*
40Ar36Ar+
40Ar38Ar+
40Ar2+
Mass
15
17
18
24
26
28
28
29
30
31
32
33
37
39
41
44
45
52
54
55
56
57
76
78
80
Element Interference8
Sc
Cr
Cr
Mn
Se
Se
Se
method elements or internal standards affected by the molecular ions,
107
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TABLE 2 (Continued).
MATRIX MOLECULAR IONS
CHLORIDE
Molecular Ion
35C10*
35C10H*
37C10*
37C10H*
Ar35Cl*
Ar37Cl*
SULPHATE
Molecular Ion
32SO*
SOH*
SO*
34SOH*
S02*, S2*
Ar32S*
Ar34S*
PHOSPHATE
Molecular Ion
PO*
POH*
P02*
ArP*
GROUP I, II METALS
Molecular Ion
ArNa*
ArK*
ArCa*
MATRIX OXIDES*
Molecular Ion
TiO
ZrO
MoO
Mass
51
52
53
54
75
77
Mass
48
49
50
51
64
72
74
Mass
47
48
63
71
Mass
63
79
80
Masses
62-66
106-112
108-116
Element Interference
V
Cr
Cr
Cr
As
Se
Element Interference
V,Cr
7 •
V
Zn
Element Interference
Cu
Element Interference
Cu
Element Interference
Ni,Cu,Zn
Ag,Cd
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.
108
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TABLE 3: INTERNAL STANDARDS AND LIMITATIONS OF USE
Internal Standard
6Lithium
Scandium
Yttrium
Rhodium
Indium
Terbium
Holmium
Lutetium
Bismuth
Mass
6
45
89
103
115
159
165
175
209
Possible Limitation
polyatomic ion interference
a,b
isobaric interference by Sn
a May be present in environmental samples.
b In some ^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.
109
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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
Thallium
Thorium
Uranium
Vanadium
Zinc
Krypton
Ruthenium
Palladium
Tin
NOTE: Isotopes recommended for analytical determination are underlined.
110
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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)(121C)
(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)("C)
(1.000)(60C)
(1.000)(82C)
(1.000)(107C)
(1.000)(205C)
(1.000)(232C)
(1.000)(238C)
(l.qpO)(51C)-(3.l27)[(53C)-(O.H3)(52C)]
(1.000)(66C)
Note
(1)
(2)
(3)
(4)
(5)
(6)
(7)
Cont.
Ill
-------
TABLE 5 (Continued)
INTERNAL STANDARDS
Element Elemental Equation
B1 (1.000)(209C)
(1.000)(115C)-(0.016)(118C)
In
Sc
Tb
Y
Note
(8)
(1.000)(45C)
(1.000)(159C)
(1.000)(89C)
C - calibration blank subtracted counts at specified mass.
(1) - correction for chloride interference with adjustment for
Se77. ArCl 75/77 ratio may be determined from the reagent
blank.
(2) - correction for MoO interference. 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.
(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 Kr82 by background subtraction.
(7) - correction for chloride interference with adjustment for
Cr53. CIO 51/53 ratio may be determined from the reagent
blank.
(8) - isobaric elemental correction for tin.
112
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TABLE 6: INSTRUMENT OPERATING CONDITIONS
FOR PRECISION AND RECOVERY DATA
Instrument
Plasma forward power
Coolant flow rate
Auxiliary flow rate
Nebulizer flow rate
Solution uptake rate
Spray chamber temperature
VG PlasmaQuad Type I
1.35 kW
13.5 L/min
0.6 L/min
0.78 L/min
0.6 mL/min
15°C
Data Acquisition
Detector mode
Rep!icate i ntegrati ons
Mass range
Dwell time
Number of MCA channels
Number of scan sweeps
Total acquisition time
Pulse counting
3
8 - 240 amu
320 MS
2048
85
3 minutes per sample
113
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TABLE 7: TOTAL RECOVERABLE METHOD DETECTION LIMITS
RECOMMENDED
MDL*
ELEMENT
ANALYTICAL MASS
AQUEOUS
M9/L
SOLIDS
mg/kg
Aluminum
Antimony
Arsenic
Barium
Beryl1i urn
Cadmium
Chromium
Cobalt
Copper
Lead
Manganese
Molybdenum
Nickel
Selenium
Silver
Thallium
Thorium
Uranium
Vanadium
Zinc
27
121
75
137
9
111
52
59
63
206,207,208
55
98
60
82
107
205
232
238
51
66
1.0
0.4
1.4
0.8
0.3
0.5
0.9
0.09
0.5
0.6
0.1
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.
0.
0.05
0.1
0.2
3.2
0.05
0.1
0.05
0.05
1.0
0.7
,2
.3
MDL concentrations are computed for original matrix with
allowance for sample dilution during preparation.
114
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TABLE 8 : PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES
DRINKING WATER
Element
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
(ad/Li (in /I)
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
(UQ/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.
115
-------
TABLE 8 : PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cent).
WELL WATER
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/L)
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 (%)
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
(UQ/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 (%)
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.
116
-------
TABLE 8 : PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont).
POND WATER
El ement
Al
Sb
As
Ba
Be ,
Cd
Cr
Co
Cu
Pb
Mn
Mo
Ni
Se
Ag
Tl
Th
U
V
Zn
Sample Low
Concn. Spike
(IM/L) (UQ/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
faa/LV
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 (%)
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
•i''
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.
117
-------
TABLE 8 : 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
Ho
Ni
Se
Ag
Tl
Th
U
V
Zn
Samp! e Low
Concn. Spike
(UQ/L) (UQ/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
(UQ/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.
118
-------
TABLE 8 : PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont).
INDUSTRIAL EFFLUENT
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
(«q/L) (UQ/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 (%)
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 (%)
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.
119
-------
TABLE 9 : PRECISION AND RECOVERY DATA IN SOLID MATRICES
EPA HAZARDOUS SOIL #884
El ement
Al
Sb
As
Ba
Be
Cd
Cr
Co
Cu
Pb
Mn
Mo
Ni
Se
Ag
Tl
Th
U
V
Zn
Sample
Concn.
(mq/kq)
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
Low+
Spike
mq/kq)
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
Average High+ Average
Recovery S(R) RPD Spike Recovery S(R) RPD
R (%} (ma/ka) R (%)
* * 100 * *
69.8 2.5 4.7 100 70.4 1.8 6.5
104.7 5.4 9.1 100 102.2 2.2 5.4
54.9 63.6 18.6 100 91.0 9.8 0.5
100.1 0.6 1.5 100 102.9 0.4 1.0
97.3 1.0 1.4 100 101.7 0.4 1.0
86.7 16.1 8.3 100 105.5 1.3 0.0
98.8 1.2 1.9 100 102.9 0.7 1.8
86.3 13.8 3.4 100 102.5 4.2 4.6
85.0 45.0 13.9 100 151.7 25.7 23.7
* * 12.7 100 85.2 10.4 2.2
95.4 1.5 2.9 100 95.2 0.7 2.0
101.7 3.8 1.0 100 102.3 0.8 0.8
79.5 7.4 26.4 100 100.7 9.4 26.5
96.1 0.6 0.5 100 94.8 0.8 2.3
94.3 1.1 3.1 100 97.9 1.0 2.9
69.8 0.6 1.3 100 76.0 2.2 7.9
100.1 0.2 0.0 100 102.9 0.0 0.0
109.2 4.2 2.3 100 106.7 1.3 2.4
87.0 27.7 5.5 100 113.4 12.9 14.1
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.
Not determined.
+ Equivalent.
120
-------
TABLE 9 : PRECISION AND RECOVERY DATA IN SOLID MATRICES (Cont).
NBS 1645 RIVER SEDIMENT
Sample 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/kq)(mq/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 (%)
*
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 m
*
81.2
107.3
98.6
87.9
95.7
*
103.1
105.2
-
-
98.4
102.2
93.9
96.2
94.4
92.3
98.5
100.7
*
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.
121
-------
TABLE 9 : PRECISION AND RECOVERY DATA IN SOLID MATRICES (Cont).
EPA ELECTROPLATING SLUDGE #286
Element
AT
Sb
As
Ba
Be
Cd
Cr
Co
Cu
Pb
Hn
Mo
Ni
Se
Ag
Tl
Th
U
V
Zn
Sample Low+
Concn. Spike
(mq/kq) mq/kq)
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 m
*
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
(mq/kq)
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
R m
*
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
-
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.
Not determined.
+ Equivalent.
122
-------
METHOD 200.9
DETERMINATION OF TRACE ELEMENTS BY STABILIZED TEMPERATURE
GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY
John T. Creed, Theodore D. Martin, Larry B. Lobring and James W. O'Dell
Inorganic Chemistry Branch
Chemistry Research Division
Revision 1.2
April 1991
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
123
-------
METHOD 200.9
DETERMINATION OF TRACE ELEMENTS BY STABILIZED TEMPERATURE
GRAPHITE FURNACE ATOMIC ABSORPTION
1. SCOPE AND APPLICATION
1.1 This method provides procedures for the determination of dissolved
and total recoverable elements in ground water, surface water,
drinking water and wastewater. This method is also applicable to
total recoverable elements in sediment, sludges, biological tissues,
and solid waste samples.
1.2 Dissolved elements are determined after suitable filtration and acid
preservation. Acid digestion procedures are required prior to the
determination of total recoverable elements. Appropriate digestion
procedures for biological tissues should be utilized prior to sample
analysis.
1.3 This method is applicable to the determination of the following
elements by stabilized temperature graphite furnace atomic
absorption spectrometry (STGFAA).
Element Chemical Abstract Services
Registry Numbers (CASRN)
Aluminum (Al) 7429-90-5
Antimony (Sb) 7440-36-0
Arsenic (As) 7440-38-2
Beryllium (Be) 7440-41-7
Cadmium (Cd) 7440-43-9
Chromium (Cr) 7440-47-3
Cobalt (Co) 7440-48-4
Copper (Cu) 7440-50-8
Iron (Fe) 7439-89-6
Lead (Pb) 7439-92-1
Manganese (Mn) 7439-96-5
Nickel (Ni) 7440-02-0
Selenium (Se) 7782-49-2
Silver (Ag) 7440-22-4
Thallium (Tl) 7440-28-0
Tin (Sn) 7440-31-5
Zinc (Zn) 7440-66-6
NOTE: Method detection limit and instrumental operating
conditions for the applicable elements are listed in Table 2.
These are intended as a guide to instrumental detection limits
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
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sample matrix, instrumentation and selected operating
conditions.
1.4 The sensitivity and limited linear dynamic range (LDR) of GFAA often
implies the need to dilute a sample prior to the 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 should be analyzed by an alternative
analytical method which has a larger LDR or which is inherently less
sensitive than GFAA.
1.5 This method should be used by analysts experienced in the use of
GFAA.
2. SUMMARY OF METHOD
2.1 This method describes the determination of applicable elements by
stabilized temperature platform graphite furnace atomic absorption
(STPGFAA). In STPGFAA the sample (and the matrix modifier, if
required) is first pipetted onto the platform or a device which
provides delayed atomization. The sample is then dried at a
relatively low temperature (~120°C) to avoid spattering. Once
dried, the sample is normally 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.
The resulting atomic cloud absorbs the element specific atomic
emission produced by a hollow cathode lamp (HCL) or a electrode!ess
discharge lamp (EDL). Because the resulting absorbance usually has
a nonspecific component associated with the actual analyte
absorbance, an instrumental background correction device is
necessary 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
(Sect. 4) must be recognized and corrected. Instrumental drift as
well as suppressions or enhancements of instrument response caused
by the sample matrix must be corrected for by the method of standard
addition (Sect. 11.5).
3. DEFINITIONS
3.1 DISSOLVED - Material that will pass through a 0.45-Aim membrane
filter assembly, prior to sample acidification.
3.2 TOTAL RECOVERABLE - The concentration of analyte determined on an
unfiltered sample following treatment with hot dilute mineral acid.
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3.5
3.6
3.3 INSTRUMENT DETECTION LIMIT (IDL) - The concentration equivalent of
an analyte signal equal to three times the standard deviation of the
calibration blank signal at the selected absorbance line.
3.4 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.
LINEAR DYNAMIC RANGE (LDR) - The concentration range over which the
analytical working curve remains linear.
LABORATORY REAGENT BLANK (LRB) - An aliquot of reagent water that is
treated exactly as a sample including exposure to all glassware,
equipment, and reagents that are used with samples. The LRB is used
to determine if method analytes or other interferences are present
in the laboratory environment, reagents or apparatus.
CALIBRATION BLANK - A volume of ASTM type I water acidified such
that the acid(s) concentration is identical to the acid(s)
concentration associated with the calibration standards.
STOCK STANDARD SOLUTION - A concentrated solution containing one
analyte prepared in the laboratory using a assayed reference
compound or purchased from a reputable commercial source.
CALIBRATION STANDARD (CAL) - A solution prepared from the stock
standard solution which is used to calibrate the instrument
response with respect to analyte concentration.
3.10 LABORATORY FORTIFIED BLANK (LFB) - An aliquot of reagent water to
which a known quantity of each method analyte is added in the
laboratory. The LFB is analyzed exactly like a sample, and its
purpose is to determine whether the method is within accepted
control limits.
3.11 LABORATORY FORTIFIED SAMPLE MATRIX (LFM) - An aliquot of an
environmental sample to which a known quantity of each 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.
3.12 QUALITY CONTROL SAMPLE (QCS) - A solution containing a known
concentration of each method analyte derived from externally
prepared test materials. The QCS is obtained from a source external
to the laboratory and is used to check laboratory performance.
3.13 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.
3.7
3.8
3.9
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3.14 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 the sample analyte concentration.
4. 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, non-
spectral and memory.
4.1.1 Spectral - Interferences resulting from the absorbance of
light by a molecule and/or an atom which is not the analyte
of interest. Spectral interferences caused by an element
only occur if 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 over 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 non-specific absorbance. The
non-specific 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.
Spectral interferences are also caused by the emission 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 produced during
atomization.
Note: A spectral interference may be manifested by
extremely high backgrounds (1.0 abs ) which may exceed the
capability of the background corrector and/or it may be
manifested as a non-analyte element which may cause a
direct spectral overlap with the analyte of interest. If
a spectral interference is suspected, the analyst is
advised to:
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* This background level is given as a guide and is
not intended to serve as an absolute value which may
be applied in all situations.
1. Dilute the sample if the analyte absorbance is
large enough to sacrifice some of the sensitivity.
This dilution may dramatically reduce a molecular
background or reduce it to the point where the
background correction device is capable of adequately
removing the remaining nonspecific component. If the
non-specific component is produced by a spectral
overlap with an interfering element, the change in
absorbance caused by dilution of the sample should
decrease in a linear fashion, provided the undiluted
and diluted sample are both within the linear range
of the interfering element.
2. If dilution is not acceptable because of the
relatively low analyte absorbance readings or the
dilution produces a linear decrease in the
nonspecific absorbance, the analyst is advised to
investigate another analyte wavelength which may
eliminate the suspected spectral interference(s).
3. If dilution and alternative spectral lines are
not acceptable, the analyst is advised to attempt to
selectively volatilize the analyte or the non-
specific component thereby eliminating the unwanted
interference(s) by atomizing the analyte in an
interference-free environment.
4. If none of the above advice is applicable and the
spectral interference persists, an alternative
analytical method which is not based on the same type
of physical/chemical principle may be necessary to
evaluate the actual analyte concentration.
4.1.2 Non-spectral - Interferences caused by sample components
which inhibit the formation of free atomic analyte atoms
during the atomization cycle. The use of a delayed
atomization device which provides stabilized temperatures is
required, because 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 a sample plus a
laboratory fortified sample matrix early within any analysis
set. From this data, immediately calculate the percent
recovery (Sect. 10.4.2). If the percent recovery is outside
the laboratory determined control limits (Sect. 10.3.3) a
potential problem should be suspected. If the result
indicates a potential matrix effect, the analyst is advised
to:
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1. Perform the method of standard addition (see Sect.
11.5); if the "percent recovery" from the method of
standard addition is drastically different from the
percent recovery from LFM, then lab contamination or
another lab related problem should be suspected and
corrected.
NOTE: If contamination is suspected, analyze the LFB
and calculate a percent recovery.
2. If the two recoveries are approximately equal* and the
response from the standard addition is dramatically
different than that which would be calculated from the
calibration curve, the sample should be suspected of a
matrix induced interference and analyzed by the method of
standard addition (Sect. 11.5).
* The limitations listed in Sect. 11.5 must be met in
order to apply these recommendations.
4.1.3 Memory interferences resulting 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. This concentration
represents the maximum concentration of analyte within a
sample which will not cause a memory interference on the
subsequent sample(s). If this concentration is exceeded, the
sample should be diluted and a blank should be analyzed (to
assure the memory affect has been eliminated) before
reanalyzing the diluted sample.
Note: Multiple clean out furnace cycles may be necessary
in order to fully utilize the LDR for certain elements.
4.1.4 Specific Element Interferences
Antimony: Antimony suffers from an interference
produced by KpS04 . 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.
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5. SAFETY
* The actual furnace temperature may vary from
instrument to instrument. Therefore, the actual
furnace temperature should be determined on an
individual bases.
Aluminum: The Pd 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. A 1% HC1 solution with
Pd used as a modifier results in a 40% loss in sensitivity
relative to the analyte in a 1% HN03 solution. The use of
Pd/Mg/H2 as a modifier reduces this suppression to about
10%.
Cadmium: The HC1 present from the digestion procedure can
influence the sensitivity for Cd. A 1% HC1 solution with
Pd used as a modifier results in a 70% loss in sensitivity
relative to the analyte in a 1% HN03 solution. The use of
Pd/Mg/H2 as a modifier reduces this suppression to less
than 10%.
Copper: Pd lines at 324.27 nm and 325.16 nm may produce
an interference on the Cu line at 324.8 nm5.
Lead: The HC1 present from the digestion procedure can
influence the sensitivity for Pb. A 1% HC1 solution with
Pd used as a modifier results in a 70% loss in sensitivity
relative to the analyte response in a 1% HNO, solution.
The use of Pd/Mg/H2 as a modifier reduces this suppression
to less than 10%.
Selenium: Iron has been shown to suppress Se response
with continuum source background correction5. 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 furnace prior to atomization.
Silver: The Pd used in the modifier preparation may have
elevated levels of Ag which will cause elevated blank
absorbances.
5.1 The toxicity or carcinogenicity of reagents 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
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 methodf'2. A
reference file of material data handling sheets should also be
available to all personnel involved in the chemical analysis.
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5.2 The graphite tube during atomization emits intense UV radiation.
Suitable precautions should be taken to protect personnel from such
a hazard.
5.3 The use of argon/hydrogen gas mixture during the dry and char steps
may evolve a considerable amount of HC1 gas. Therefore, adequate
ventilation is required.
6. APPARATUS AND EQUIPMENT
6.1 GRAPHITE FURNACE ATOMIC ABSORBANCE SPECTROPHOTOMETER
6.1.1 The GFAA spectrometer must be capable of programmed heating
of the graphite tube and the associated delayed atomization
device. The instrument should be equipped with an adequate
background correction device capable of removing undesirable
non-specific absorbance over the spectral region of interest.
The capability to record relatively fast (< 1 sec) transient
signals and evaluate data on a peak area basis is preferred.
In addition, a recirculating refrigeration bath is
recommended for improved reproduc-ibility of furnace
temperatures. The data shown in the tables were obtained
using the stabilized temperature platform and Zeeman
background correction.
6.1.2 Single element hollow cathode lamps or single element
electrodeless discharge lamps along with the associated power
supplies.
6.1.3 Argon gas supply (high-purity grade, 99.99%).
6.1.4 A 5% hydrogen in argon gas mix and the necessary hardware to
use this gas mixture during specific furnace cycles.
6.1.5 Autosampler - Although not specifically required, the use of
an autosampler is highly recommended.
6.2 GRAPHITE FURNACE OPERATING CONDITIONS—A guide to experimental
conditions for the applicable elements are shown in Table 2
6.3 SAMPLE PROCESSING EQUIPMENT
6.3.1 Balance - Analytical, capable of accurately weighing to
0.1 mg.
6.3.2 Hot Plate - Corning PC100 or equivalent.
6.3.3 Centrifuge - Steel cabinet with guard bowl, electric timer
and brake.
6.3.4 Drying Oven capable of ± 3°C temperature control.
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6.4 LABWARE - The determination of trace level elements requires a
consideration of potential sources of contamination and analyte
losses. 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 contributing contaminants through surface
desorption or leaching and/or depleting element concentrations
through adsorption processes. All reusable labware (glass, quartz,
polyethylene, Teflon etc.), including the sample container, should
be cleaned prior to use. Labware should be soaked overnight and
thoroughly washed with laboratory-grade detergent and water, rinsed
with water, and soaked for four hours in a mixture of dilute nitric
and hydrochloric acid (1+2+9), followed by rinsing with ASTM type I
water and oven drying.
NOTE: Chromic acid must not be used for cleaning glassware.
6.4.1 Glassware - Volumetric flasks and graduated cylinders.
6.4.2 Assorted calibrated pipettes.
6.4.3 Conical Phillips beakers, 250-mL with 50-mm watch glasses.
Griffin beakers, 250-mL with 75-mm watch glasses.
6.4.4 Storage bottles - Narrow mouth bottles, Teflon FEP
(fluorinated ethylene propylene) with Tefzel ETFE (ethylene
tetrafluorethylene) screw closure, 125-mL and 250-mL
capacities.
6.4.5 Wash bottle - One piece stem, Teflon FEP bottle with Tefzel
ETFE screw closure, 125-mL capacity.
7. REAGENTS AND CONSUMABLE MATERIALS
7.1 REAGENTS - Reagents may contain elemental impurities which might
affect analytical data. Because of the high sensitivity of GFAA,
high-purity reagents should be used whenever possible. All acids
used for this method must be ultra high-purity grade. Suitable
acids are available from a number of manufacturers or may be
prepared by sub-boiling distillation.
7.1.1 Nitric acid, concentrated (sp.gr. 1.41) (CASRN 7697-37-2).
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 Nitric acid (1+9) - Add 100 mL cone, to 400 mL of ASTM type I
water and dilute to 1 L.
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7.1.4 Hydrochloric acid, concentrated (sp.gr. 1.19) (CASRN 7647-01-
0).
7.1.5 Hydrochloric acid (1+4) - Add 200 mL cone, hydrochloric acid
to 400 ml ASTM type I water and dilute to 1000 ml.
7.1.6 Tartaric acid. ACS reagent grade (CASRN 87-69-4).
7.1.7 Matrix Modifier, dissolve 300 mg Palladium (Pd) powder in
concentrated HNO, (1 ml of HN03, adding 10 mL of concentrated
HC1 if necessary). Dissolve 200 mg.of Mg(N03)2 in ASTM type
1 water. Pour the two solutions together and dilute to 100
ml with ASTM type 1 water.
Note: It is recommended that the matrix modifier be
analyzed separately in order to assess the contribution of
the modifier to the overall laboratory blank.
7.1.8 Ammonium hydroxide, concentrated (sp.gr. 0.902) (CASRN 1336-
21-6).
7.2 WATER - For all sample preparation and dilutions, ASTM type I water
(ASTM D1193) is required. Suitable water may be prepared by passing
distilled water through a mixed bed of anion and cation exchange
resins.
7.3 STANDARD STOCK SOLUTION - May be purchased from a reputable
commercial source or prepared from ultra high-purity grade chemicals
or metal (99.99 - 99.999% pure). All salts should be dried for 1 h
at 105°C, unless otherwise specified. (CAUTION: Many metal salts
are extremely toxic if inhaled or swallowed. Wash hands thoroughly
after handling). The stock solution should be stored in Teflon
bottles. The following procedures may be used for preparing stan-
dard 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 /zg 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 ASTM type I water. Heat
until the volume is reduced to 2 ml. Cool and dilute to
100 mL with ASTM type I water.
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7.3.2 Antimony solution, stock, 1 ml = 1000 ng 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 ASTM type I water and 0.15g tartaric acid.
Warm the solution to dissolve the white precipitate. Cool
and dilute to 100 ml with ASTM type I water.
7.3.3 Arsenic solution, stock, 1 ml = 1000 /LUJ As: Dissolve
0.1320 g As203 in a mixture of 50 ml ASTM type I 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 ASTM type I water.
7.3.4 Beryllium solution, stock 1 ml = 500 /Ltg Be: Dissolve 1.965 g
BeS04.4HpO (DO NOT DRY) in 50 ml ASTM Type I water. Add 2 ml
cone, nitric acid. Dilute to 200 mL with ASTM type I water.
7.3.5 Cadmium solution, stock, 1 ml = 1000 /ig Cd: Pickle Cd 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 ASTM type I water.
7.3.6 Chromium solution, stock, 1 ml = 1000 jug Cr: Dissolve
0.1923g Cr03 in a solution mixture of 10 ml ASTM type I water
and 1 ml cone, nitric acid. Dilute to 100 mL with ASTM type
I water.
7.3.7 Cobalt solution, stock 1 mL = 1000 jug Co: Pickle Co 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 ASTM type I water.
7.3.8 Copper solution, stock, 1 mL = 1000 ^9 Cu: Pickle Cu 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 ASTM type I water.
7.3.9 Iron solution, stock, 1 mL = 1000 ng Fe: Pickle Fe metal in
(1+9) hydrochloric acid to an exact weight of 0.100 g.
Dissolve in 10 mL (1+1) hydrochloric acid, heating to effect
solution. Cool and dilute to 100 mL with ASTM type I water.
7.3.10 Lead solution, stock, 1 mL = 1000 ;ug Pb: Dissolve 0.1599 g
PbN03 in 5 mL (1+1) nitric acid. Dilute to 100 mL with ASTM
type I water.
7.3.11 Manganese solution, stock, 1 mL = 1000 jug Mn: Pickle
manganese flake 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 ASTM type I
water.
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7.3.12 Nickel solution, stock, 1 ml = 1000 ng Ni: Dissolve 0.100 g
nickel powder in 5 ml cone, nitric acid, heating to effect
solution. Cool and dilute to 100 ml with ASTM type I water.
7.3.13 Selenium solution, stock, 1 ml = 1000 /zg Se: Dissolve
0.1405 g Se02 in 20 ml ASTM type I water. Dilute to 100 ml
with ASTM type I water.
7.3.14 Silver solution, stock, 1 ml = 1000 /Ltg 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 ASTM type I water.
Store in amber container.
7.3.15 Thallium solution, stock 1 ml = 500 jug Tl: Dissolve 0.1303 g
T1NO, in a solution mixture of 10 ml ASTM type I water and 2
ml cone, nitric acid. Dilute to 200 ml with ASTM type I
water.
7.3.16 Tin solution, stock, 1 ml = 1000 ^g Sn: Dissolve 0.100 g Sn
shot in 20 ml (1+1) hydrochloric acid, heating to effect
solution. Cool and dilute to 100 ml with (1+1) hydrochloric
acid.
7.3.17 Zinc solution, stock, 1 ml = 1000 /zg 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 ASTM type I water.
7.4 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 (Sect. 7.6).
NOTE: The appropriate acid diluent for dissolved elements in
water samples is 1% HN03. For total recoverable elements in
waters the appropriate acid diluent is 2% HN03 and 1% HC1.
Finally, the appropriate acid diluent for total recoverable
elements in solid samples is 2% HN03 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.
7.5 BLANKS - Two types of blanks are required for this method. A
calibration blank is used to establish the analytical calibration
curve and the laboratory reagent blank (LRB) is used to assess
possible contamination from the sample preparation procedure and to
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7.5.2
7.6
7.7
assess spectral background. All diluent acids should be made from
concentrated acids (Sects. 7.1.1, 7.1.4) and ASTM type I water.
7.5.1 Calibration blank - Consists of the appropriate acid diluent
(Sect. 7.4 note) (HC1/HN03) in ASTM type I water.
Laboratory reagent blank (preparation blank) must contain all
the reagents in the same volumes as used in processing the
samples. The preparation blank must be carried through the
entire sample digestion and preparation scheme.
QUALITY CONTROL SAMPLE - Quality control samples are available from
various sources. Dilute (with the appropriate acid (HC1/HNO,) blank
solution) an appropriate aliquot of analyte such that the resulting
solution will result in an absorbance of approximately 0.1.
LABORATORY FORTIFIED BLANK - To an aliquot of laboratory reagent
blank, add an aliquot of the stock standard to provide a final
concentration which will produce an absorbance of approximately 0.1
for the analyte. The fortified blank must be carried through the
entire sample digestion and preparation scheme.
8. 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, acid preservation etc.
should be performed at the time of sample collection or as soon
thereafter as practically possible.
8.2 For the determination of dissolved elements, the sample should be
filtered through a 0.45-jum membrane filter. Use a portion of the
sample to rinse the filter assembly, discard and then collect the
required volume of filtrate. Acidify the filtrate with (1+1)
nitric acid immediately following filtration to a pH of less than
two.
8.3 For the determination of total recoverable elements in aqueous
samples, acidify with (1+1) nitric acid at the time of collection to
a pH of less than two. The sample should not be filtered prior to
analysis.
NOTE: Samples that cannot be acid preserved at the time of
collection because of sampling limitations or transport
restrictions, should be acidified with nitric acid to pH <2
upon receipt in the laboratory (normally, 3 mL of (1+1)
nitric acid per liter of sample is sufficient for most
ambient and drinking water samples). Following
acidification, the sample should be held for a minimum of
16 h before withdrawing an aliquot for sample processing.
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8.4 Solid samples usually require no preservation prior to analysis
other than storage at 4°C.
9. CALIBRATION AND STANDARDIZATION
9.1 CALIBRATION - Demonstration and documentation of acceptable initial
calibration is required before any samples are analyzed arid is
required periodically throughout sample analysis as dictated by
results of continuing calibration checks. After initial calibration
is successful, a calibration check is required at the beginning and
end of each period during which analyses are performed.
9.1.1 Initiate proper operating configuration of instrument and
data system. Allow a period of not less than 30 min for the
instrument to warm up if an EDL is to be used.
9.1.2 Instrument stability must be demonstrated by analyzing a
standard solution of a concentration 20 times the IDL a
minimum of five times with the resulting relative standard
deviation of absorbance signals less than 5%.
9.1.3 Initial calibration. The instrument must be calibrated for
the analyte to be determined using the calibration blank
(Sect. 7.5.1) and calibration standards prepared at three or
more concentration levels within the linear dynamic range of
the analyte.
9.2 INSTRUMENT PERFORMANCE - Check the performance of the instrument and
verify the calibration using data gathered from analyses of
calibration blanks, calibration standards and the quality control
sample.
9.2.1 After the calibration has been established, it must be
initially verified for the analyte by analyzing the QCS
(Sect. 7.6). If measurements exceed ± 10% of the
established QCS value, the analysis should be terminated, the
source of the problem identified and corrected, the
instrument recalibrated, and the new calibration must be
verified before continuing analyses.
9.2.2 To verify that the instrument is properly calibrated on a
continuing basis, analyze the calibration blank and an
intermediate concentration calibration standard as surrogate
samples after every ten analyses. The results of the
analyses of the standard will indicate whether the
calibration remains valid. If the indicated concentration of
any analyte deviates from the true concentration by more than
10%, the instrument must be recalibrated and the response of
the QCS checked as in Sect. 9.2.1. After the QCS sample has
met specifications, the previous ten samples must be
reanalyzed in groups of five with an intermediate
137
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concentration calibration standard analyzed after every fifth
sample. If the intermediate concentration calibration
standard is found to deviate by more than 10%, the analyst is
instructed to identify the source of instrumental drift.
NOTE: If the sample matrix is responsible for the
calibration drift and/or the sample matrix is affecting
analyte response, it may be necessary to perform standard
additions in order to assess an analyte concentration
(Sect. 11.5).
10. QUALITY CONTROL (PC)
10.1 FORMAL QUALITY CONTROL- The minimum requirements of this QC 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.
10.2 INITIAL DEMONSTRATION OF PERFORMANCE
10.2.1 The initial demonstration of performance is used to
characterize instrument performance (MDLs and linear calibra-
tion ranges) for analyses conducted by this method.
10.2.2 Method detection limits (MDL) - The method detection limit
should be established for the analyte, using reagent water
(blank) fortified at a concentration of two to five times the
estimated detection limit5. 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.
Method detection limits should be determined every six months
or whenever a significant change in background or instrument
response is expected.
10.2.3 Linear calibration ranges - Linear calibration ranges are
metal dependent. The upper limit of the linear calibration
range should be established by determining the signal
responses from a minimum of four different concentration
138
-------
standards, one of which is close to the upper limit of the
linear range. The linear calibration range which may be used
for the analysis of samples should be judged by the analyst
from the resulting data. Linear calibration ranges should be
determined every six months or whenever a significant change
in instrument response maybe expected.
10.3 ASSESSING LABORATORY PERFORMANCE - REAGENT AND FORTIFIED BLANKS
10.3.1 Laboratory reagent blank (LRB) - The laboratory must analyze
at least one LRB (Sect. 7.5.2) with each set of samples.
Reagent blank data are used to assess contamination from the
laboratory environment and to characterize spectral
background from the reagents used in sample processing. If
an analyte value in the reagent blank exceeds its determined
MDL, then laboratory or reagent contamination should be
suspected. Any determined source of contamination should be
corrected and the samples reanalyzed.
10.3.2 Laboratory fortified blank (LFB) - The laboratory must
analyze at least one LFB (Sect. 7.7) with each set of
samples. Calculate accuracy as percent recovery (Sect.
10.4.2). If the recovery of any analyte falls outside the
control limits (Sect. 10.3.3), that analyte is judged out of
control, and the source of the problem should be identified
and resolved before continuing analyses.
10.3.3 Until sufficient data (usually a minimum of 20 to 30
analyses) become available, a laboratory should assess
laboratory performance against recovery limits of 80-120%.
When sufficient internal performance data become 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
After each 5-10 new recovery measurements, new control limits
should be calculated using only the most recent 20 to 30 data
points.
NOTE: Antimony and Aluminum do manifest relatively low
percent recoveries (see Table 1A, NBS River Sediment 1645).
10.4 ASSESSING ANALYTE RECOVERY - LABORATORY FORTIFIED SAMPLE MATRIX
10.4.1 The laboratory must fortify a minimum of 10% of the samples
or one fortified sample per set, whichever is greater.
Ideally for solid samples, the concentration added should be
approximately equal to 0.1 abs units after the solution has
139
-------
been diluted. In other words if the sample (after dilution)
results in an absorbance of 0.05, ideally the laboratory
fortified sample will result in an absorbance of 0.150 (after
dilution). Over time, samples from all routine sample
sources should be fortified.
10.4.2 Calculate the percent recovery for the analyte, corrected for
background concentrations measured in the unfortified sample,
and compare these values to the control limits established in
Sect. 10.3.3 for the analyses of LFBs. Fortified recovery
calculations are not required if the fortified concentration
is less than 10% of the sample background concentration.
Percent recovery may be calculated in units appropriate to
the matrix, using the following equation:
R = (Cs - C) x 100
S
where,
R = percent recovery.
Cs = fortified sample concentration.
C = sample background concentration.
S = concentration equivalent of the fortified sample.
10.4.3 If the recovery of the analyte on the fortified sample falls
outside the designated range, and the laboratory performance
on the LFB for the analyte is shown to be in control
(Sect. 10.3) the recovery problem encountered with the
fortified sample is judged to be matrix related (Sect. 4),
not system related. The data obtained for that analyte
should be verified with the methods of standard additions
(Sect. 11.5).
10.5 QUALITY CONTROL SAMPLES (QCS) - Each quarter, the laboratory should
analyze one or more QCS (if available). If criteria provided with
the QCS are not met, corrective action should be taken and
documented.
11. PROCEDURE
11.1 SAMPLE PREPARATION - DISSOLVED ELEMENTS
11.1.1 For the determination of dissolved elements in drinking
water, wastewater, ground and surface waters, take a 100-mL
(± ImL) aliquot of the filtered acid preserved sample, and
add 1 mL of concentrated nitric acid. The sample is now
ready for analysis. Allowance should be made in the
calculations for the appropriate dilution factors.
140
-------
NOTE: If a precipitate is formed during.acidification,
.'' transport or storage, the sample aliquot must be treated
using the procedure In-Sect.-, 11.2.1 prior to analysis.
11.2 SAMPLE PREPARATION - TOTAL RECOVERABLE ELEMENTS.
11.2.1 For the determination of total recoverable elements in water
. or waste water, take a 100-mL (± 1 mL) aliquot from a well
mixed, acid preserved sample and transfer it to a 250-mL
Griffin beaker. Add 1 mL of concentrated HNO, and 0.5 mL of
concentrated HC1. Heat the sample on a hot plate at 85°C
until the volume has been reduced to approximately 20 mL,
ensuring that the sample does not boil. (A spare beaker
containing 20 mL of water can be used as a gauge.)
NOTE: For proper heating adjust the temperature control of
the hot plate such that an uncovered beaker containing
50 mL of water located in the center of the hot plate can
be maintained at approximately but no higher than 85°C.
Evaporation time for 100 mL of sample at 85°C is
approximately 2 h with the rate of evaporation rapidly
increasing as the sample volume approaches 20 mL.
Cover the beaker with a watch glass and reflux for 30 min.
Slight boiling may occur but vigorous boiling- should be
avoided. Allow to cool and quantitatively transfer to
either a 50-mL volumetric or a 50-mL class A stoppered
graduated cylinder. Dilute to volume with ASTM type I water
and mix. Centrifuge the sample or allow to stand overnight
to separate insoluble material. The sample is now ready for
analysis. Prior to the analysis of samples the calibration
standards must be analyzed and the calibration verified using
a QC sample (Sect. 9). Once the calibration has been
verified, the instrument is ready for sample analysis.
Because the effects of various matrices on the stability of
diluted samples cannot be characterized, samples should be
analyzed as soon as possible after preparation.
11.2.2 For the determination of total recoverable elements in solid
samples (sludge, soils, and sediments), mix the sample
thoroughly to achieve homogeneity and weigh accurately a 1.0
± 0.01 g portion of the sample. Transfer to a 250-mL
Phillips beaker. Add 4 mL (1+1) nitric acid and 10 mL (1+4)
HC1. Cover with a watch glass. Heat the sample on a hot
plate and gently reflux for 30 min. Very slight boiling may
occur, however, vigorous boiling must be avoided to prevent
the loss of the HC1 azeotrope.
141
-------
NOTE: For proper heating adjust the temperature control
of the hot plate such that an uncovered Griffin beaker
containing 50 ml of water located in the center of the hot
plate can be maintained at a temperature approximately but
no higher than 85°C.
Allow the sample to cool and quantitatively transfer to
either 100-mL (± 1 mL) volumetric flask or a 100-mL class A
stoppered graduate cylinder. Dilute to volume with ASTM type
I water and mix. Centrifuge the sample or allow to stand
overnight to separate insoluble material. The sample is now
ready for analysis. Prior to the analysis of samples the
calibration standards must be analyzed and the calibration
verified using a QC sample (Sect. 9). Once the calibration
has been verified, the instrument is ready for sample
analysis. Because the effects of various matrices on the
stability of diluted samples cannot be characterized, samples
should be analyzed as soon as possible after preparation.
NOTE: Determine the percent solids in the sample for use
in calculations and for reporting data on a dry weight
Dasis.
11.2.3 Appropriate digestion procedures for biological tissues
should be utilized prior to sample analysis.
11.3 For every new or unusual matrix, it is highly recommended that an
inductively coupled plasma atomic emission spectrometer be used to
screen for high element concentrations. Information gained from
this may be used to prevent potential damage of the instrument and
better estimate which elements may require analysis by qraohite
furnace. v
11.4 Samples having concentrations higher than the established linear
dynamic range should be diluted into range and reanalyzed If
methods of standard additions are required, follow the instructions
i n oscL* 11«o.
11.5 STANDARD ADDITIONS - If methods of standard addition are required
the following procedure is recommended.
11.5.1 The standard addition technique4 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 siqnal
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
142
-------
each of volume Vx, 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 V of the solvent. The analytical signals of A
and B are measured and corrected for nonanalyte signals. The
unknown sample concentration cx is calculated:
SBV3CS
(SA-SB) Vx
where SA and SB are the analytical signals (corrected for the
blank) of solutions A and B, respectively. Vs and cs should
be chosen so that S. is roughly twice SB on the average. It
is best if Vs is made much less than Vx, and thus cs is much
greater than c , 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 front 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 the
same 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.
12. CALCULATIONS
12.1 Do not report element concentrations below the determined MDL.
12.2 For aqueous samples prepared by total recoverable procedure (Sect.
11.2.1), multiply solution concentrations by the appropriate
dilution factor. Round the data to the tenths place and report the
data in M9/L with up to three significant figures.
12.3 For solid samples prepared by total recoverable procedure (Sect.
11.2.2) round the solution concentration (M9/L in the analysis
solution) to the tenths place and multiply by the dilution factor.
Data should be reported to a tenth mg/kg up to three significant
figures taking into account the percent solids if the data are
reported on a dry weight* basis.
143
-------
* The dry weight should be determined on a separate sample
aliquot if the sample is available. The dry weight can be
determined by transferring a uniform 1-g aliquot to an
n9 d1Sh and drin the S t0 a constant wei'9ht
12.4 If additional dilutions were performed, the appropriate dilution
factor must be applied to sample values.
12'5 Ihf Ldata 0^?jned du!:in9 the ^alyses provide an indication of
the quality of the sample data and should be provided with the
sample results.
13. PRECISION AND ACCURACY
13 '* ?,™L0^taHn^d Tru? S]?gle ! ab°ratory 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
c !gei'i o amplrs were PrePared "sing the procedure described in
aSf«« **?: For,?ach matrix, five replicates were analyzed and an
ann^9? °f-the re.Pllcates used for determining the sample background
concentration. Two further pairs of duplicates were fSrtifiec I 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
^h dd,1*1on> Table 1D-p contains a single laboratory testing
? ? in ac>ue?us media including drinking water, pond water
V? Sri 3mp 6S uere PrePared "sing the procedure described
. 11.2.1. For each aqueous matrix, five replicates were
h aC 3n avera9e of the ^eplicates 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
n
in
14. REFERENCES
1.
2.
3.
"OSHA Safety and Health Standards, General Industry," (29CFR 1910)
S3£°1976 and HeaUh Administration> OSHA 2206, revised
"Proposed OSHA Safety and Health Standards, Laboratories "
SSlyP24]°1986Safety aPd HeaUh Administrat1on> Federal Register,
Code of Federal Regulations 40, Ch. 1, Pt. 136, Appendix B.
144
-------
4. Winefordner, J.D., "Trace Analysis: Spectroscopic Methods for
Elements," Chemical Analysis. Vol. 46, pp. 41-42.
5. Waltz, B., G. Schlemmar and J. R. Mudakavi, JAAS, 1988, 3, 695.
145
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TABLE 2. RECOMMENDED GRAPHITE FURNACE OPERATING CONDITIONS
AND RECOMMENDED MATRIX MODIFIER (i'3)
Element
Ag
A17
As'
Be
Cd
Co
Cr
Cu
Fe
Mn
r\t
Pb
Sb7
c* (
Se'
Sn7
Tl
Zn
Wave-
length
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
213.9
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
0.7
Temperature
Char
1000
1700
1300
1200
800
1400
1650
1300
1400
1400
1400
1250
1100
1000
14008
1000
700
(C)5
Atom.
1800
2600
2200
2500
1600
2500
26006
26006
2400
2200
2500
2000
2000
2000
2300
1600
1800
MDL4
(M9/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
0.3
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
tor a 11 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 second atomization is necessary to quantitatively remove the analyte
from the graphite furnace.
7) An electrode!ess discharge lamp was used for this element.
8) An additional low temperature (approximately 200°C) prechar is
recommended.
9) Pd modifier was determined to have trace level contamination of this
element.
152
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Method 200.10
DETERMINATION OF TRACE ELEMENTS IN MARINE WATERS BY ON-LINE CHELATION
PRECONCENTRATION AND INDUCTIVELY COUPLED PLASMA - MASS SPECTROMETRY
Stephen E. Long
Technology Applications, Inc.
and
Theodore D. Martin
Inorganic Chemistry Branch
Chemistry Research Division
Revision 1.4
April 1991
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
153
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METHOD 200.10
DS5H5NATIOM OF TRACE ELEMENTS IN MARINE WATERS BY ON-LINE CHELATION
PRECONCENTRATION AND INDUCTIVELY COUPLED PLASMA - MASS SPECTROMETRY
1. SCOPE AND APPLICATION
1.1 This method describes procedures for preconcentration and
determination of total recoverable trace elements in marine waters
including estuanne water, seawater and brines.
1.2 Acid sol utilization is required prior to the determination of total
recoverable elements to facilitate breakdown of complexes or
colloids which might influence trace element recoveries. This
method should only be used for preconcentration and determination of
trace elements in aqueous samples.
1.3 This method is applicable to the following elements:
1.4
1.5
Element Chemical Abstract Services
Registry Numbers (CASRN)
Cadmium (Cd) 7440-43-9
Cobalt (Co) 7440-48-4
Copper (Cu) 7440-50-8
Lead (Pb) 7439-92-1
• Nickel (Ni) 7440-02-0
Uranium (U) 7440-61-1
Vanadium (V) 7440-62-2
Method detection limits (MDLs) for these elements will be dependent
on the specific instrumentation employed and the selected operating
conditions. However, the MDLs should be essentially independent of
the matrix because elimination of the matrix is a feature of the
method. MDLs in reagent water, which were determined usinq the
procedure described in Sect. 10.2.2, are listed in Table 1.
A minimum of six months experience in the use of commercial
)?rDrMcfn*ation for induct1vely coupled plasma mass spectrometry
rro MC I ls recommended. Specific information regarding the use of
Meth d 200 8^ determinat1on of trace elements may be found in USEPA
2. SUMMARY OF METHOD
2.1
This method is used to preconcentrate trace elements using an
inn nodi acetate functionalized chelating resin(2'3). Following acid
solubilization, the sample is buffered prior to chelating column
154
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entry using an on-line system. Group I and II metals, as well as
most anions, are selectively separated from the analytes by elution
with ammonium acetate at pH 5.5. The analytes are subsequently
eluted into a simplified matrix consisting of dilute nitric acid and
are determined by ICP-MS using a directly coupled on-line
configuration.
3. DEFINITIONS
3.1 TOTAL RECOVERABLE - The concentration of analyte determined on an
unfiltered sample following treatment with hot dilute mineral acid.
3.2 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.
3.3 LINEAR DYNAMIC RANGE (LDR) - The concentration range over which the
analytical working curve remains linear.
3.4 LABORATORY REAGENT BLANK (LRB) (preparation blank) - An aliquot of
reagent water that is treated exactly as a sample including exposure
to all labware, 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.
3.5 CALIBRATION BLANK - A volume of ASTM type I water acidified with the
same acid matrix as is present in the calibration standards.
3 6 INTERNAL STANDARD - Pure analyte(s) added to a solution in known
amount(s) and used to measure the relative responses of other method
analytes that are components of the same solution. The internal
standard must be an analyte that is not a sample component.
3.7 STOCK STANDARD SOLUTION - A concentrated solution containing one or
more analytes prepared in the laboratory using assayed reference
compounds or purchased from a reputable commercial source.
3.8 CALIBRATION STANDARD (CAL) - A solution prepared from the stock
standard solution(s) which is used to calibrate the instrument
response with respect to analyte concentration.
3.9 TUNING SOLUTION - A solution which is used to determine acceptable
instrument performance prior to calibration and sample analyses.
3.10 LABORATORY FORTIFIED BLANK (LFB) - An aliquot of reagent water 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 method is within accepted
control limits.
155
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3.11 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!ike 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 the concentrations found.
3.12 QUALITY CONTROL SAMPLE (QCS) - A solution containing known
concentrations of method analytes which is used to fortify an
aliquot of LRB matrix. The QCS is obtained from a source external
to the laboratory and is used to check laboratory performance.
INTERFERENCES
4.1
4.2
4.3
A discussion of interferences relating to the use of ICP-MS may be
found in USEPA Method 200.8<1). A principal advantage of this
method is the selective elimination of species giving rise to
polyatomic spectral interferences on certain transition metals (e.g
removal of the chloride interference on vanadium). As the majority
of the sample matrix is removed, matrix induced physical
interferences are also substantially reduced.
Low recoveries may be encountered in the preconcentration cycle if
the trace elements are complexed by competing chelators in the
sample or are present as colloidal material. Acid solubilization
pretreatment is employed to improve analyte recovery and to minimize
adsorption, hydrolysis and precipitation effects.
Memory interferences from the chelating system may be encountered
especially after analyzing a sample containing high concentrations
of the analytes. A thorough column rinsing sequence following
elution of the analytes is necessary to minimize such interferences.
5. SAFETY
5.1
Each chemical reagent used in this method should be regarded as a
potential health hazard and exposure to these reagents 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
available to all personnel involved in the chemical analysis.
5.2 Analytical plasma sources emit radiofrequency radiation in addition
to intense UV radiation. Suitable precautions should be taken to
protect personnel from such hazards.
156
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6. APPARATUS AND EQUIPMENT
6.1 PRECONCENTRATION SYSTEM - System containing no metal parts in the
analyte flow path, configured as shown in Figure 1.
6.1.1 Column - Macroporous iminodiacetate chelating resin (Dionex
Metpac CC-1 or equivalent).
6.1.2 Sample loop - 10 ml_ loop constructed from narrow bore, high-
pressure inert tubing, Tefzel ETFE (ethylene tetra-
fluoroethylene) or equivalent.
6.1.3 Eluent pumping system (PI) - Programmable flow, high pressure
pumping system,.capable of delivering either one of two
eluents at a pressure up to 2000 psi and a flow rate of 1-5
mL/min.
6.1.4 Auxiliary pumps - On line buffer pump (P2), piston pump
(Dionex QIC pump or equivalent) for delivering 2M ammonium
acetate buffer solution; carrier pump (P3). peristaltic pump
(Gilson Minipuls or equivalent) for delivering 1% nitric acid
carrier solution; sample pump (P4). peristaltic pump for
loading sample loop.
6.1.5 Control valves - Inert double stack, pneumatically operated
four-way slider valves with connectors.
6.1.5.1 Argon gas supply regulated at 80-100 psi.
6.1.6 Solution reservoirs - Inert containers, e.g. high density
polyethylene (HOPE) for holding eluent and carrier reagents.
6.1.7 Tubing - High pressure, narrow bore, inert tubing (e.g.
Tefzel ETFE or equivalent) for interconnection of pumps/valve
assemblies and a minimum length for connection of the
preconcentration system to the ICP-MS instrument.
6.2 INDUCTIVELY COUPLED PLASMA - MASS SPECTROMETER
6.2.1 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
extended dynamic range detection system.
6.2.2 Argon gas supply (high-purity grade, 99.99%).
6.2.3 A mass-flow controller on the nebulizer gas supply is
recommended. A water-cooled spray chamber may be of benefit
in reducing some types of interferences (e.g., polyatomic
oxide species).
157
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6.3
6.2.4 Operating conditions - Because of the diversity of instrument
hardware, no detailed instrument operating conditions are
provided. The analyst is advised to follow the recommended
operating conditions provided by the manufacturer.
LABWARE - For the determination of trace elements, contamination and
loss are of critical consideration. Potential contamination sources
include improperly cleaned laboratory apparatus and general
contamination within the laboratory environment. 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. For these
reasons, borosilicate glass is not recommended for use with this
method. All labware in contact with the sample should be cleaned
prior to use. Labware may be soaked overnight and thoroughly washed
with laboratory-grade detergent and water, rinsed with water, and
soaked for 4 h in a mixture of dilute nitric and hydrochloric acids,
followed by rinsing with ASTM type I water and oven drying.
6.3.1 Griffin beakers, 250 ml, polytetrafluoroethylene (PTFE) or
quartz.
6.3.2 Storage bottles - Narrow mouth bottles, Teflon FEP
(fluorinated ethylene propylene), or HOPE, 125 mL and 250 ml
capacities.
6.4 SAMPLE PROCESSING EQUIPMENT
6.4.1 Air displacement pipetter - Digital pipet system capable of
delivering volumes from 10 to 2500 #L with an assortment of
metal-free, disposable pipet tips.
6.4.2 Balances - Analytical balance, capable of accurately weighing
to ± 0.1 mg; top pan balance, accurate to ± O.Olg.
6.4.3 Hot plate - Corning PC100 or equivalent.
6.4.4 Centrifuge - Steel cabinet with guard bowl, electric timer
and brake.
6.4.5 Drying oven - Gravity convection oven with thermostatic
control capable of maintaining 105°C ± 5°C.
6.4.6 pH meter - Bench mounted or hand-held electrode system with a
resolution of ± 0.1 pH units.
158
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7. REAGENTS AND CONSUMABLE MATERIALS
7.1 WATER - For all sample preparation and dilutions, ASTM type I water
(ASTM QM'93) is required.
7.2 Reagents may contain elemental impurities which might affect the
integrity of analytical data. Owing to the high sensitivity of this
method, ultra high-purity reagents must be used unless otherwise
specified. To minimize contamination, reagents should be prepared
directly in their designated containers where possible.
7.2.1 Acetic acid, glacial (sp. gr. 1.05).
7.2.2 Ammonium hydroxide (20%).
7.2.3 Ammonium acetate buffer 1M, pH 5.5 - Add 58 ml (60.5 g) of
glacial acetic acid to 600 ml of ASTM type I water. Add
65 ml (60 g) of 20% ammonium hydroxide and mix. Check the pH
of the resulting solution by withdrawing a small aliquot and
testing with a calibrated pH meter, adjusting the solution to
pH 5.5 ± 0.1 with small volumes of acetic acid or ammonium
hydroxide as necessary. Cool and dilute to 1 L with ASTM
type I water.
7.2.4 Ammonium acetate buffer 2M, pH 5.5 - Prepare as for Sect.
7.2.3 using 116 ml (121 g) glacial acetic acid and 130 ml
(120 g) 20% ammonium hydroxide, diluted to 1000 ml with ASTM
type I water.
NOTE: The ammonium acetate buffer solutions may be further
purified by passing them through the chelating column at a
flow rate of 5.0 mL/min. With reference to Figure 1, pump
the buffer solution through the column using pump PI, with
valves A and B off and valve C on. Collect the purified
solution in a container at the waste outlet. Following this,
elute the collected contaminants from the column using 1.25M
nitric acid for 5 min at a flow rate of 4.0 mL/min.
7.2.5 Nitric acid, concentrated (sp.gr. 1.41).
7.2.5.1 Nitric acid 1.25M - Dilute 79 mL (112 g) cone, nitric
acid to 1000 mL with ASTM type I water.
7.2.5.2 Nitric acid 1% - Dilute 10 mL cone, nitric acid to
1000 mL with ASTM type I water.
7.2.5.3 Nitric acid (1+1) - Dilute 500 mL cone, nitric acid
to 1000 mL with ASTM type I water.
7.2.5.4 Nitric acid (1+9) - Dilute 100 mL cone, nitric acid
to 1000 mL with ASTM type I water.
159
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7.2.6 Oxalic acid dihydrate (CASRN 6153-56-6), 0.2M - Dissolve
25.2 g reagent grade C2Hp04.2HpO in 250 ml ASTM type I water
and dilute to 1000 ml with ASTM type I water. CAUTION -
Oxalic acid is toxic, handle with care.
7.3 STANDARD STOCK SOLUTIONS - 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 one
hour at 105°C, unless otherwise specified. (CAUTION - Many metal
salts are extremely toxic if inhaled or swallowed. Wash hands
thoroughly after handling). Stock solutions should be stored in
plastic bottles. 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 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 ASTM type I water.
7.3.2 Cobalt solution, stock 1 mL = 1000 /zg Co: Pickle cobalt
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 ASTM type I water.
7.3.3 Copper solution, stock 1 ml = 1000 /zg 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 ASTM type I water.
7.3.4 Indium solution, stock 1 mL = 1000 fig 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 ASTM type I water.
7.3.5 Lead solution, stock 1 mL = 1000 /ng Pb: Dissolve 0.1599 g
PbN03 in 5 mL (1+1) nitric acid. Dilute to 100 mL with ASTM
type I water.
7.3.6 Nickel solution, stock 1 mL = 1000 jzg Ni: Dissolve 0.100 g
nickel powder in 5 mL cone, nitric acid, heating to effect
solution. Cool and dilute to 100 mL with ASTM type I water.
7.3.7 Terbium solution, stock 1 mL = 1000 /zg Tb: Dissolve 0.1176 g
Tb407 in 5 mL cone, nitric acid, heating to effect solution.
Cool and dilute to 100 mL with ASTM type I water.
160
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7.4
7.5
7.6
7.3.8 Uranium solution, stock 1 ml = 1000 jug U: Dissolve 0.2110 g
UOp(N03)2.6H20 (DO NOT DRY) in 20 mL ASTM type I water and
dilute to 100 ml with ASTM type I water.
7.3.9 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 ASTM type I water.
7.3.10 Yttrium solution, stock 1 ml = 1000 /zg Y: Dissolve 0.1270 g
Y20, in 5 ml (1+1) nitric acid, heating to effect solution.
Cool and dilute to 100 ml with ASTM type I water.
MULTI-ELEMENT STOCK STANDARD SOLUTION - Care must be taken in the
preparation of multi-element 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, new FEP or HOPE bottles for storage and monitored
periodically for stability. A multi-element stock standard solution
containing the elements, cadmium, cobalt, copper, lead, nickel,
uranium and vanadium (1 mL = 10 /jg) may be prepared by diluting 1 mL
of each single element stock in the list to 100 mL with ASTM type I
water containing 1% (v/v) nitric acid.
7.4.1 Preparation of calibration standards - Fresh multi-element
calibration standards should be prepared weekly. Dilute the
stock multi-element standard solution in 1% (v/v) nitric acid
to levels appropriate to the required operating range. 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. A
suggested mid-range concentration is 10 /*g/L.
BLANKS - In addition to the laboratory fortified blank, two types of
blanks are required for this method. A calibration blank is used to
establish the analytical calibration curve, and the laboratory
reagent blank is used to assess possible contamination from the
sample preparation procedure.
7.5.1 Calibration blank - Consists of
type I water.
(v/v) nitric acid in ASTM
7.5.2 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 entire sample
digestion and preparation scheme.
TUNING SOLUTION - This solution is used for instrument tuning and
mass calibration prior to analysis (Sect. 9.2). The solution is
prepared by mixing nickel, yttrium, indium, terbium and lead stock
161
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solutions (Sect. 7.3) in 1% (v/v) nitric acid to produce a
concentration of 100 /tg/L of each element.
7.7 QUALITY CONTROL SAMPLE (QCS) - A quality control sample having
certified concentrations of the analytes of interest should be
obtained from a source outside the laboratory. Dilute the QCS if
necessary with 1% nitric acid, such that the analyte concentrations
fall within the proposed instrument calibration range.
7.8 LABORATORY FORTIFIED BLANK (LFB)- To an aliquot of LRB, add aliquots
from the multi-element stock standard (Sect. 7.4) to produce a final
concentration of 10 fig/I for each analyte. The fortified blank must
be carried through the entire sample pretreatment and analytical
scheme.
8. SAMPLE COLLECTION. PRESERVATION AND STORAGE
8.1 For the determination of total recoverable elements in aqueous
samples, acidify with (1+1) nitric acid at the time of collection to
a pH of less than two. The sample should not be filtered prior to
analysis.
NOTE: Samples that cannot be acid preserved at the time of
collection because of sampling limitations or transport
restrictions, should be acidified with nitric acid to pH < 2 upon
receipt in the laboratory. Following acidification, the sample
should be held for 16 h before withdrawing an aliquot for sample
processing.
9. CALIBRATION AND STANDARDIZATION
9.1 Initiate proper operating configuration of ICP-MS 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 nickel isotopes 60,61,62. 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.
9.2 Instrument stability must be demonstrated by analyzing the tuning
solution (Sect. 7.6) a minimum of five times with resulting relative
standard deviations of absolute signals for all analytes of less
than 5%.
9.3 Prior to initial calibration, set up proper instrument software
routines for quantitative analysis and connect the ICP-MS instrument
to the preconcentration apparatus. The instrument must be
calibrated for the analytes of interest using the calibration blank
(Sect. 7.5.1) and calibration standard (Sect. 7.4.1) prepared at one
or more concentration levels. The calibration solutions should be
162
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processed through the preconcentration system using the procedures
described in Sect. 11.
9.4 Demonstration and documentation of acceptable initial calibration is
required before any samples are analyzed and is required
periodically throughout sample analysis as dictated by results of
continuing calibration checks. After initial calibration is
successful, a calibration check is required at the beginning and end
of each period during which analyses are performed and at requisite
intervals.
9.4.1 After the calibration has been established, it must be
initially verified for all analytes by analyzing the QCS
(Sect. 7.7). If measurements exceed ± 15% of the
established QCS value, the analysis should be terminated, the
source of the problem identified and corrected, the
instrument recalibrated and the new calibration verified
before continuing analyses.
9.4.2 To verify that the instrument is properly calibrated on a
continuing basis, run the calibration blank (Sect. 7.5.1) and
calibration standards (Sect. 7.4.1) as surrogate samples
after every ten analyses. The results of the analyses of the
standards will indicate whether the calibration remains
valid. If the indicated concentration of any analyte
deviates from the true concentration by more than 15%,
reanalyze the standard. If the analyte is again outside the
15% limit, the instrument must be recalibrated and the
previous ten samples reanalyzed. The instrument responses
from the calibration check may be used for recalioration
purposes.
9.5 INTERNAL STANDARDIZATION - Internal standardization should be used
in all analyses to correct for instrument drift. Internal standards
may be added directly to the samples and standards prior to
preconcentration or by mixing with the chelating column carrier
effluent prior to nebulization using a peristaltic pump and a mixing
coil. Information on the use of internal standards may be found in
Method 200.8(1). NOTE: Lithium and bismuth should not be used as
internal standards using the direct addition method as they are not
efficiently concentrated on the imino-diacetate column.
10. QUALITY CONTROL
10.1 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, fortified
blanks and samples as a continuing check on performance. The
laboratory should maintain performance records that define the
quality of the data generated.
163
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10.2 INITIAL DEMONSTRATION OF PERFORMANCE
10.2.1 The initial demonstration of performance is used to
characterize instrument performance (method detection limits
and linear calibration ranges) for analyses conducted by this
method.
10.2.2 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
limitc }. 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.
MDLs should be determined every six months or whenever a
significant change in background or instrument response is
expected.
10.2.3 Linear calibration ranges - The upper limit of the linear
calibration range should be established for each analyte.
Linear calibration ranges should be determined every six
months or whenever a significant change in instrument
response is expected.
10.3 ASSESSING LABORATORY PERFORMANCE - REAGENT AND FORTIFIED BLANKS
10.3.1 Laboratory reagent blank (LRB) - The laboratory must analyze
at least one LRB (Sect. 7.5.2) with each set of samples. LRB
data are used to assess contamination from the laboratory
environment. If an analyte value in the LRB exceeds its
determined MDL, then laboratory or reagent contamination
should be suspected. Any determined source of contamination
should be corrected and the samples reanalyzed.
10.3.2 Laboratory fortified blank (LFB) - The laboratory must
analyze at least one LFB (Sect. 7.8) with each batch of
samples. Calculate accuracy as percent recovery (Sect.
10.4.2) If the recovery of any analyte falls outside the
control limits (Sect. 10.3.3), that analyte is judged out of
control, and the source of the problem should be identified
and resolved before continuing analyses.
164
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10.3.3 Until sufficient LFB data become available from within the
laboratory (usually a minimum of 20 to 30 analyses), the
laboratory should assess laboratory performance against
recovery limits of 85-115%. 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
After each five to ten new recovery measurements, new control
limits should be calculated using only the most recent twenty
to thirty data points.
10.4 ASSESSING ANALYTE RECOVERY - LABORATORY FORTIFIED SAMPLE MATRIX
10.4.1 The laboratory must add a known amount of each analyte to a
minimum of 10% of the routine samples or one sample per
sample set, whichever is greater. The analyte concentrations
should be the same as those used in the LFB (Sect. 10.3.2).
Over time, samples from all routine sample sources should be
fortified.
10.4.2 Calculate the percent recovery for each analyte, corrected
for the concentrations measured in the unfortified sample,
and compare these values to the control limits established in
Sect. 10.3.3 for the analyses of LFBs. Recovery calculations
are not required if the concentration of the analyte added is
less than 10% of the sample concentration. Percent recovery
may be calculated in units appropriate to the matrix, using
the following equation:
cs - c
R = x 100
where, R = percent recovery
Cs = fortified sample concentration
C = sample concentration
s = concentration equivalent of
fortifier added to sample.
10.4.3 If recovery of any analyte falls outside the designated range
and laboratory performance for that analyte is shown to be in
control (Sect. 10.3), the recovery problem encountered with
the fortified sample is judged to be matrix related, not
system related. The result for that analyte in the
unfortified sample must be labelled "suspect/matrix" to
inform the data user that the results are suspect due to
matrix effects.
165
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11. PROCEDURE
11.1 SAMPLE PREPARATION - TOTAL RECOVERABLE ELEMENTS
11.1.1 For the determination of total recoverable elements, take a
100 mL aliquot from a well mixed, acid preserved sample and
transfer to a 250-mL Griffin beaker. Add 1 mL of
concentrated nitric acid and heat on a hot plate at 85°C
until the volume has been reduced to approximately 25 mL,
ensuring that the sample does not boil. Cover the beaker
with a watch glass and reflux for 30 min. Slight boiling may
occur but vigorous boiling should be avoided. Allow to cool
and dilute to 100 mL with ASTM type I water. Centrifuge the
sample or allow to stand overnight to separate insoluble
material.
11.2 Prior to first use, the preconcentration system should be thoroughly
cleaned and decontaminated using 0.2M oxalic acid.
11.2.1 Place approximately 500 mL 0.2M oxalic acid in the eluent and
carrier solution containers and fill the sample loop with
0.2M oxalic acid using the sample pump (P4) at a flow rate of
3-5 mL/min. With the preconcentration system disconnected
from the ICP-MS instrument, use the pump program sequence
listed in Table 2, to flush the complete system with oxalic
acid. Repeat the flush sequence three times.
11.2.2 Repeat the sequence described in Sect. 11.2.1 using 1.25M
nitric acid and again using ASTM type I water in place of the
0.2M oxalic acid.
11.2.3 Rinse the containers thoroughly with ASTM type I water, fill
them with their designated reagents (see Figure 1) and run
through the sequence in Table 2 once to prime the pump and
all eluent lines with the correct reagents.
11.3 Initiate ICP-MS instrument operating configuration. Tune and
calibrate the instrument for the analytes of interest (Sect. 9).
11.4 Establish instrument software run procedures for quantitative
analysis. Because the analytes are eluted from the preconcentration
column in a transient manner, it is recommended that the instrument
software is configured in a rapid scan/peak hopping mode.
11.5 Reconnect the preconcentration system to the ICP-MS instrument.
With valves A and B in the off position and valve C in the on
position, load sample through the sample loop to waste using pump P4
for 4 min at 4 mL/min. Switch on the carrier pump (P3) and pump 1%
nitric acid to the nebulizer of the ICP-MS instrument at a flow rate
of 0.8-1.0 mL/min.
166
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11.6 Switch on the buffer pump (P2), and pump 2M ammonium acetate at a
flow rate of 1 mL/min.
11 7 Preconcentration of the sample may be achieved by running through an
eluent pump program (PI) sequence similar to that illustrated in
Table 2. The exact timing of this sequence should be modified
according to the internal volume of the connecting tubing and the
specific hardware configuration used.
11.7.1 Inject sample - With valves A, B and C on, load sample from
the loop onto the column using 1M ammonium acetate for 4.5
min at 4.0 mL/min. The analytes are retained on the column,
while the majority of the matrix is passed through to waste.
11.7.2 Elute analytes - Turn off valves A and B and begin eluting
the analytes by pumping 1.25M nitric acid through the column
at 4.0 mL/min, then turn off valve C and pump the eluted
analytes into the ICP-MS instrument at 1.0 mL/min. Initiate
ICP-MS software data acquisition and integrate the eluted
analyte profiles.
11.7.3 Column Reconditioning - Turn on valve C to direct column
effluent to waste, and pump 1.25M nitric acid, 1M ammonium
acetate, 1.25M nitric acid and 1M ammonium acetate
alternately through the column at 4.0 mL/min. During this
process, the next sample can be loaded into the sample loop
using the sample pump (P4).
11.8 Repeat the sequence described in Sect. 11.7 for each sample to be
analyzed. At the end of the analytical run leave the column filled
with 1M ammonium acetate buffer until it is next used.
11.9 Samples having concentrations higher than the established linear
dynamic range should be diluted into range and re-analyzed.
12. CALCULATIONS
12.1 Analytical isotopes and elemental equations recommended for sample
data calculations are listed in Table 3. Sample data should be
reported in units of Mg/L. 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 Reported values should be calibration blank subtracted. If
additional dilutions were made to any samples, the appropriate
factor should be applied to the calculated sample concentrations.
167
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12.4 Data values should be corrected for instrument drift by the
application of internal standardization. Corrections for
characterized spectral interferences should be applied to the data.
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. PRECISION AND ACCURACY
13.1 Experimental conditions used for single laboratory testing of the
method are summarized in Table 4.
13.2 Data obtained from single laboratory testing of the method are
summarized in Tables 5 and 6 for two reference water samples
consisting of National Research Council Canada (NRCC), Estuarine
Water (SLEW-1) and Seawater (NASS-2). The samples were prepared
using the procedure described in Sect. 11.2.1. For each matrix,
three replicates were analyzed and the average of the replicates
used for determining the sample concentration for each analyte. Two
further sets of three replicates were fortified at different
concentration levels, one set at 0.5 /zg/L, the other at 10 /xg/L.
The sample concentration, mean percent recovery, and the relative
standard deviation of the fortified replicates are listed for each
method analyte. The reference material certificate values are also
listed for comparison.
168
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14. REFERENCES
1. USEPA Method 200.8, Office of Research and Development, USEPA,
Cincinnati, Ohio, August 1990.
2. A. Siraraks, H.M. Kingston and J.M. Riviello,
Anal Chem. 62 1185 (1990).
3. E.M. Heithmar, T.A. Hinners, J.T. Rowan and J.M. Riviello,
Anal Chem. 62 857 (1990).
4. "OSHA Safety and Health Standards, General Industry," (29 CFR 1910),
Occupational Safety and Health Administration, OSHA 2206, revised
January 1976.
5. "Proposed OSHA Safety and Health Standards, Laboratories,"
Occupational Safety and Health Administration, Federal
Register, July 24, 1986.
6. Code of Federal Regulations 40, Ch. 1, Pt. 136 Appendix B.
169
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TABLE 1: TOTAL RECOVERABLE METHOD DETECTION LIMITS FOR REAGENT WATER
ELEMENT
RECOMMENDED
ANALYTICAL MASS
MDL
Cadmium
Cobalt
Copper
Lead
Nickel
Uranium
Vanadium
111
59
63
206,207,208
60
238
51
0.041
0.021
0.023
0.074
0.081
0.031
0.014
170
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TABLE 2: Eluent PUMP PROGRAMMING SEQUENCE FOR PRECONCENTRATION
OF TRACE ELEMENTS
Time
(min)
0.0
4.5
5.1
5.5
7.5
8.0
10.0
11.0
12.5
Flow
mL/min
4.0
4.0
1.0
1.0
4.0
4.0
4.0
4.0
0.0
Eluent
1M ammonium acetate
1.25M nitric acid
1.25M nitric acid
1.25M nitric acid
1.25M nitric acid
1M ammonium acetate
1.25M nitric acid
1M ammonium acetate
Valve
A,B
ON
ON
OFF
OFF
OFF
OFF
OFF
OFF
OFF
Valve
C
ON
ON
ON
OFF
ON
ON
ON
ON
ON
171
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TABLE 3: RECOMMENDED ANALYTICAL ISOTOPES AND ELEMENTAL EQUATIONS
FOR DATA CALCULATIONS
Element Isotope
Elemental Equation
Note
Cd 106,108,111,114
Co 59
Cu 63,65
Pb 206,207.208
Ni 60
U 238
V 51
(1.000)(111C)-(1.073)[(108C)-(0.712)(106C)]
(1.000)(59C)
(1.000)(63C)
(1.000)(206C)+(1.000)(207C)+(1.000)(208C)
(1.000)(60C)
(1.000)(238C)
(1.000)(51C)
(1)
(2)
C - calibration blank subtracted counts at specified mass
(1) - correction for MoO interference. An additional isobaric
elemental correction should be made if palladium is present.
(Z) - allowance for isotopic variability of lead isotopes.
NOTE: As a minimum, all isotopes listed should be monitored. Isotopes
recommended for analytical determination are underlined.
172
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TABLE 4: EXPERIMENTAL CONDITIONS FOR SINGLE LABORATORY VALIDATION
Chromatography
Instrument
Preconcentration column
Dionex chelation system
Dionex MetPac CC-1
ICP-MS Instrument Conditions
Instrument
Plasma forward power
Coolant flow rate
Auxiliary flow rate
Nebulizer flow rate
Internal standards
Data Acquisition
Detector mode
Mass range
Dwell time
Number of MCA channels
Number of scan sweeps
VG PlasmaQuad Type I
1.35 kW
13.5 L/min
0.6 L/min
0.78 L/min
Sc, Y, In, Tb
Pulse counting
45-240 amu
160 /is
2048
250
173
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TABLE 5: PRECISION AND RECOVERY DATA FOR ESTUARINE WATER (SLEW-1)
Analyte
Cd
Co
Cu
Pb
Ni
mmm
Certificate
(09/L)
0.018
0.046
1.76
0.028
0.743
••»•»
••••••IMBMB
Sample
Concn.
(09/L)
<0.041
0.078
1.6
<0.074
0.83
1.1
1.4
Spike
Addition
(0g/L)
0.5
0.5
0.5
0.5
0.5
0.5
0.5
Average
Recovery
(%)
94.8
102.8
106.0
100.2
100.0
96.7
100.0
^••^•^
RSD
(%)
9.8
4.0
2.7
4.0
1.5
7.4
3.2
^^^_^^^__
••^^^•^^•^^••^H
Spike
Addition
(09/L)
10
10
10
10
10
10
10
Average
Recovery
(%)
99.6
96.6
96.0
106.9
102.0
98.1
97.0
RSD
(°/o)
1.1
1.4
4.8
5.8
2.1
3.6
4.5
— No certificate value
TABLE 6: PRECISION AND RECOVERY DATA FOR SEAWATER (NASS-2)
Analyte
Cd
Co
Cu
Pb
Ni
U
Certificate
0.029
0.004
0.109
0.039
0.257
3.00
^™~
Sample
Concn.
(pg/L)
<0.041
<0.021
0.12
<0.074
0.23
3.0
1.7
Spike
Addition
(/KJ/L)
0.5
0.5
0.5
0.5
0.5
0.5
0.5
^•^•^•^^^n
Average
Recovery
101.8
98.9
95.8
100.6
102.2
94.0
104.0
(^•i^M^HI
RSD
1.0
3.0
2.3
8.5
2.3
0.7
3.4
^••^•^•^•••i
Spike
Addition
(fig/L)
10
10
10
10
10
10
10
•••••••^•M
Average
Recovery
96.4
99.2
93.1
92.1
98.2
98.4
109.2
mtmmm
(%*
3.7
1.7
0.9
2.6
1.2
1.7
3.7
— No certificate value
174
-------
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o
o
X
LU
£
V)
-z.
o
I
O
O
LU
DC
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LL
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Z)
CD
LL
-z.
o
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LU
CC
175
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-------
METHOD 200.11
DETERMINATION OF METALS IN FISH TISSUE BY
INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY
Theodore D. Martin, Eleanor R. Martin
and
Larry B. Lobring
Inorganic Chemistry Branch
Chemistry Research Division
and
Gerald D. McKee
Office of the Director
Revision 2.1
April 1991
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
177
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METHOD 200.11
DETERMINATION OF METALS IN FISH TISSUE BY
INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY
1. SCOPE AND APPLICATION
1.1 This method is an inductively coupled plasma (ICP)-atomic emission
spectrometnc procedure for use in determination of naturally
occurring and accumulated toxic metals in the edible tissue portion
(fillet) of the fish. The tissue must be taken from a fresh, not
previously frozen, fish to prevent analyte loss or tissue
contamination due to cell lysis and resulting fluid exchange. The
method is not intended to be used for analysis of dried fish tissue
This method is applicable to the determination of the following
metals: 3
Analvte
1.2
1.3
Aluminum (Al)
Antimony (Sb)
Arsenic (As)
Beryllium (Be)
Cadmium (Cd)
Chromium (Cr)
Copper (Cu)
Lead (Pb)
Nickel (Ni)
Selenium (Se)
Thallium (Tl)
Zinc (Zn)
Chemical Abstract Services
Registry Numbers (CASRN)
7429-
7440-
7440-
7440-
7440-
7440-
7440-
7439-
7440-
7782-
7440-
7440-
-90-5
-36-0
-38-2
•41-7
•43-9
•47-3
50-8
92-1
02-0
49-2
28-0
66-6
This method also may be used for spectrochemical determination of
other elements commonly found in fish tissue. Specific analvtes
included are the following:
Analvte
Calcium (Ca)
Iron (Fe)
Magnesium (Mg)
Phosphorus (P)
Potassium (K)
Sodium (Na)
Chemical Abstract Services
Registry Numbers (CAS RN)
7440-70-2
7439-89-6
7439-95-4
7723-14-0
7440-09-7
7440-23-5
Specific instrumental operating conditions are given and should be
used whenever possible. However, because of the differences
between various makes and models of spectrometers, the analyst
should follow the instrument manufacturer's instructions in
178
-------
adapting the instrument's operation to approximate the recommended
conditions given in this method.
1.4 Table 1 lists the recommended wavelengths with locations for
background correction for the metals presently included in this
method. Also listed in Table 1 are typical method detection limits
(MDLs)1 for certain metals determined in fish tissue using
conventional pneumatic nebulization for sample introduction into
the ICP.
1 5 Once the tissue samples have been collected, approximately 20 fish
fillet samples including the mandatory quality control samples can
be analyzed using this method during the 1.5 day work period
required to complete the analysis.
2. SUMMARY OF METHOD
21 A 1 to 2 g sample of fish tissue is taken from a fresh (not
previously frozen) fish and transferred to a preweighed, labeled
polysulfone Oak Ridge type centrifuge tube. The tissue is
dissociated using tetramethylammonium hydroxide ' , low heat and
vortex mixing. The following day, the metals in the resulting
colloidal suspension are acid solubilized with nitric acid and heat,
and then diluted with deionized, distilled water to a weight volume
ratio equal to 1 g fish tissue per 10 ml of solution. The diluted
sample is vortex mixed, centrifuged and finally the acidified
aqueous solution is analyzed by direct aspiration background
corrected ICP atomic emission spectrometry. The determined metal
concentration is reported as microgram/gram (^g/g) wet fish tissue
weight.
2.2 The basis of the method determination step is the measurement of
atomic emission by optical spectroscopy. The sample is nebulized
and the aerosol that is produced is transported to the plasma torch
where excitation occurs. Characteristic atomic-line emission
specta are produced by a radio-frequency ICP. The spectra are
dispersed by a grating spectrometer and the intensities of the
lines are monitored by photomultiplier tubes. The photocurrents
from the photomultiplier tubes are processed and controlled by a
computer system. Background correction is required to compensate
for the variable background contribution of fish matrix and
reagents to the analyte determination. The location recommended
for background correction for each analyte is given in Table 1.
3. DEFINITIONS
3.1 FISH TISSUE - The skinless edible muscle tissue of the fish
commonly referred to as the fillet.
179
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3.2 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.
3.3 CALIBRATION BLANK - A volume of deionized, distilled water
containing all reagents used to prepare the tissue for analyses
The calibration Manlr ic a ™™ e+,^,-^ and is used to calibra{e
3.4 FIELD DUPLICATES (FD1 and FD2) - Two separate samples collected at
the same time and place under identical circumstances and treated
exactly the same throughout field and laboratory procedures
Analyses of FD1 and FD2 give a measure of the precision associated
with camniQ ™-n^,_ preservation, and storage, as well as with
3.5
hdrSYt^?G-NT,BLAf,(LRB).T A" a11quot of tetramethylammonium
hydroxide that is treated exactly as a sample including exposure to
all glassware, equipment, and reagents that are used with other
samples. The LRB is used to determine if method analytes or other
n ^ lab°rat°ry env1™"ment> ^agents,
.(FRB) I An emP^ Oak Rid9e Polysulfone sample
? 1S ^eated as a sample in all respects, including
samP]in9 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. 10.3.2).
3.7 LABORATORY PERFORMANCE CHECK SOLUTION (LPC) - A solution of method
analytes used to evaluate the performance of the instrument system
with respect to a defined set of method criteria (Sect. 7.10.1).
3'8
tABShAThRif FORTIFIED.BLANK (LFB) - An aliquot of tetramethylammonium
to which known quantities of the method analytes are added in the
laboratory. The LFB is analyzed exactly like a sample and its
tKhnifti! d?termine whether the method is in control and whether
the laboratory is capable of making accurate and precise
measurements at the required method detection limit (Sect. 10.3.4).
3'9
tABSRif FORTI™ SAMPLE MATRIX (LFM) - An aliquot of fish tissue
to which known quantities of the method analytes are added in the
T6 LFM-1S aalzed exactly 11k^ a samPle> and Its
n *- exactly 11k 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
background
3.10 STOCK STANDARD SOLUTION - A concentrated solution containing a
single certified standard that is a method analyte, or a
180
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concentrated solution of a single analyte prepared in the laboratory
with an assayed reference compound. Stock standard solutions are
used to prepare primary dilution standards (Sect. 7.6).
3.11 PRIMARY DILUTION STANDARD SOLUTION - A solution of several analytes
prepared in the laboratory from stock standard solutions and diluted
as needed to prepared calibration solutions and other needed analyte
solutions (Sect. 7.7).
3.12 CALIBRATION STANDARD (CAL) - A solution prepared from the primary
dilution standard solution. The CAL solutions are used to calibrate
the instrument response with respect to analyte concentration
(Sect. 7.9).
3.13 QUALITY CONTROL SAMPLE (QCS) - A solution of method analytes of
known concentrations which is used to fortify an aliquot of LRB
matrix. The QCS is obtained from a source external to the
laboratory and used to check laboratory performance with externally
prepared test materials (Sect. 10.2.2).
4. INTERFERENCES
4.1 Occurrences of chromium contamination of biological samples from^
the use of stainless steel have been reported in the literature.
Use of special cutting implements and dissecting board made from
materials that are not of interest is recommended. Knife blades
made of titanium with Teflon handles have been successfully used.
4.2 Sample contamination and losses are held to a minimum because the
collected sample is preserved, processed and analyzed in the same
polysulfone centrifuge tube. However, the stability of metals in
the analysis solution is not fully documented and therefore, the
sample should be analyzed within 24 h after completion of the
preparation procedure (Sects. 11.2 to 11.7).
4.3 The processed sample ready for analysis will contain a precipitate
and possibly floatable solids as a surface layer partially covering
the analysis solution. Nevertheless, physical occlusion of metals
in these solids is not expected. Percent recoveries of all metal
concentrations added, except antimony, are near or exceed 90%
(Sect. 13.4.)
4.4 Because all samples are diluted to the same weight volume ratio
(1 g/10 mL), all samples of the same type of fish tissue have
similar concentrations of the major constituents in the matrix.
These major constituent elements (Ca, K, Mg, Na and P) do not
suppress analyte signal intensities or cause interelement spectral
interferences for the wavelengths and analytical conditions
recommended. However, these elements represent a small portion
(<1500mg/L) of the approximate 5% dissolved solids in the solution
matrix that is aspirated. Tetramethylammonium hydroxide accounts
for the majority of the matrix and is believed to undergo chemical
181
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4.5
4.6
change during sample preparation (Sect. 11); this causes slight
shifts in background intensity and molecular band contribution to
wavelength signals near 190 nanometers (nm). Although background
correction adjacent to the wavelength will compensate for the
majority of the broad band interferences, LRB (Sect. 3.5) sub-
traction must be used to provide the additional correction needed
for the wavelengths of As (193.7 nm), Se (196.0 nm) and Th
(190.8 nm).
Dissolved solids exceeding 1500 to 2000 mg/L can cause a reduction
in atomic emission signal intensities. In this method, because the
calibration standard and sample solutions both contain approximately
5% dissolved solids, any resulting matrix effect is minimized. Of
greater importance is that partial clogging of the instrument
nebulizer and torch impinger tube does not occur.
The number of interelement spectral interferences in the fish
tissue matrix is minimal. Listed below are all interelement
correction factors determined for the wavelengths and background
correction locations recommended in this method. Although these
factors are only applicable to the instrument used in the
development of this method, they can be used as a guide and are
evidence that, except for fortified samples, most fish tissue
analyses do not require interelement correction factors. It
should be noted that if a listed interferant is present at a
concentration of 10 fig/g or less, its apparent concentration on the
analyte channel is less than the analyte's determined MDL.
INTERELEMENT CORRECTION FACTORS
Analvte Interferant Factor
As
As
As
Cr
Cr
Cr
Pb
Pb
Sb
Sb
Se
Zn
Zn
Al
Be
Ni
Cu
Ni
Fe
Al
Cu
Cr
Ni
Fe
Cu
Ni
+0.0080
-0.0027
-0.0056
-0.0007
+0.0006
-0.0003
-0.234
+0.0008
+0.0150
-0.0087
-0.0205
+0.0013
+0.0039
A 1 Mg/g concentration of interferant would either add to or
subtract from the analyte an apparent concentration in jug/g equal
to the value of the correction factor.
182
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4.7 The following "off-the-line" background correction locations-should
be avoided because of existing spectral interference.
4.7.1 The low side (- 0.07 nm) of the 190.8 nm Th wavelength has a
spectral interference from phosphorus.
4.7.2 Background correction on the low side of the 193.7 nm As
wavelength below - 0.06 nm may result in a severe negative
bias.
4.7.3 The high side (+ 0.07 nm) of the 196.0 nm Se wavelength has a
severe undefined spectral interference originating from the
tetramethylammonium hydroxide.
4.7.4 Background correction on the low side of the 259.9 nm Fe
wavelength below - 0.06 nm may result in spectral
interference from 259.8 nm Fe wavelength.
4.7.5 The low side (- 0.05 nm) of the 308.2 nm Al wavelength has a
spectral interference from argon.
4.7.6 The low side (- 0.04 nm) of the 213.8 nm Zn wavelength
read in the 2nd order has a weak spectral interference from
magnesium.
5. 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 Precautions should also be taken to minimize potential bacterial
infections from handling and dissecting fish. Basic good house-
keeping and sanitation practices and use of rubber or plastic
gloves are recommended.
5.3 Mobile and remote sampling locations should be equipped with a
communication system to summon help in case of an emergency. It is
recommended that field personnel not work alone.
5.4 Material safety data sheets for all chemical reagents should be
available to and understood by all personnel using this method.
Specifically, tetramethylammonium hydroxide (25%) 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. APPARATUS AND EQUIPMENT
6.1 TISSUE DISSECTING EQUIPMENT
183
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6.1.1. Dissecting Board: Polyethylene or other inert, nonmetallic
material; any non-wetting, easy-to-clean or disposable
surface is suitable. Adhesive backed Teflon or plastic
film may be convenient to use.
6.1.2 Forceps: Plastic, Teflon or Teflon coated.
6.1.3 Surgical Blades: Disposable stainless steel with stainless
steel or plastic handle (Sect. 4.1).
6.1.4 Scissors: Stainless steel.
6.1.5 Plastic bags with watertight seal, metal free.
6.1.6 Label tape: Self-adhesive, vinyl-coated marking tape,
solvent resistant, usable from -23°C to 122°C.
6.1.7 Polyvinyl chloride or rubber gloves, talc-free.
6.2 Labware - All reusable glassware, polysulfone and Teflon containers
must be soaked and washed with detergent, rinsed with tap water,
soaked for 4 h in a mixture of dilute nitric and hydrochloric acid
(1+2+9), rinsed again with tap water followed by deionized,
distilled water (Sect. 7.1) and oven drying. The use of chromic
acid must be avoided.
6.2.1 Glassware: Class A volumetric flasks of various volumes,
assorted calibrated pipettes and beakers.
6.2.2 Oak Ridge type centrifuge tubes: 30-mL capacity, polysulfone
tube with polypropylene screw closure (available from most
suppliers of laboratory equipment).
6.2.3 Storage bottles: Narrow-mouth bottles, Teflon FEP
(fluorinated ethylene propylene) with Tefzel ETFE
(ethylene tetrafluorethylene) screw closure, 125-mL and
250-mL capacities.
6.2.4 Wash bottle: One-piece stem, Teflon FEP bottle with
Tefzel ETFE screw closure, 125-mL capacity.
6.3 SAMPLE PROCESSING EQUIPMENT
6.3.1 Air Displacement Pipetter: Digital pipet capable of
delivering volumes ranging from 0.1 to 2500 microliters with
an assortment of high quality disposable pipet tips.
6.3.2 Hot Plate: Ceramic top, graduated dial 90°C to 450°C
(Corning PC100 or equivalent).
184
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6.3.3 Test tube rack: Polycarbonate tube size 25-30 mm, 3 x 8
array.
6.3.4 Single pan balance capable of weighing to the nearest 0.01 g.
6.3.5 Analytical balance capable of weighing to the nearest
0.0001 g.
6.3.6 Vortex mixer with neoprene mixing head and built-in rheostat
control.
6.3.7 Centrifuge: Steel cabinet with guard bowl, capable of
reaching 2000 r.p.m. compatible with centrifuge tubes
(Sect. 6.2.3), electric timer and brake. (International
Centrifuge, Universal Model UV or equivalent.)
6.3.8 Drying oven: Gravity convection oven, with thermostatic
control capable of maintaining 65°C and 100°C ± 5°C with an
interior dimension of no smaller than 14" x 6" x 6".
6.4 ANALYTICAL INSTRUMENTATION
6.4.1 The ICP instrument may be a simultaneous or sequential
spectrometer system that uses ionized argon gas as the
plasma. However, the system and the processing of
background corrected signals must be computer controlled.
The instrument must be capable of meeting and complying with
the requirements and description of the technique given in
Sect. 2.2. The instrument must be equipped with a nebulizer
and torch impinger tube that has an orifice capable of
accepting 5% dissolved solids.
6.4.2 A variable speed peristaltic pump is required to deliver
both standard and sample solutions to the nebulizer.
6.4.3 The use of mass flow controllers to regulate the argon
flow rates, especially through the nebulizer, are highly
recommended. Their use will provide more exacting control of
reproducible plasma conditions.
7. REAGENTS AND CONSUMABLE MATERIAL
7.1 Deionized, distilled water: Prepare by passing distilled water
through a mixed bed of cation and anion exchange resins. Use
deionized, distilled water for the preparation of all reagents and
as dilution or rinse water. The purity of this water must be
equivalent to ASTM Type II reagent water of Specification D 1193.
7.2 Nitric acid (HN03), cone, (sp.gr. 1.41) (CASRN 7697-37-2), ACS
reagent grade or equivalent. Redistilled acid is acceptable.
185
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7.3
7.4
7.5
7.6
7.2.1 Nitric acid, (1+1): Add 500 mL cone. HNO, (Sect. 7.2) to 400
ml deionized, distilled water (Sect. 7.1) and dilute to 1 L.
7.2.2 Nitric acid, (1 + 9): Add 100 mL cone. HNO, (Sect. 7.2) to
400 mL deionized distilled water (Sect. 7.1) and dilute to
X L *
Hydrochloric acid (HC1), cone. (sp. gr. 1.19, CASRN 7647-01-0),
ACS reagent grade or equivalent.
7.3.1 Hydrochloric acid, (1+1): Add 500 mL cone. HC1 (Sect. 7.3)
to 400 ml deionized, distilled water (Sect. 7.1) and dilute
to 1 L.
Tetramethylammonium hydroxide [(CH3)4NOH], (CASRN 75-59-2), TMAH 25%
aqueous solution, electronic grade 99.9999% (metals basis) ALFA
#20932 or equivalent.
Ammonium hydroxide (NH,OH) (CASRN 1336-21-6), ACS reagent grade or
equivalent (sp. gr. 0.902).
Standard stock solutions may be purchased or prepared from ultra-
high purity grade chemicals or metals. All salts must be dried
for 1 h at 105°C unless specified otherwise. (CAUTION: Wash hands
thoroughly after handling). Typical stock solution preparation
procedures follow.
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.
7.6.1 Aluminum solution, stock (1 ml = 1000 p,g Al) - Pickle
aluminum metal in warm (1+1) hydrochloric acid to an exact
weight of 0.100 g. Dissolve in an acid mixture of 5 mL
(1+1) hydrochloric acid and 1 mL cone, nitric acid in a
beaker. Warm gently to effect solution. When solution is
complete, transfer quantitatively to a 100-mL volumetric
flask and dilute to the mark with deionized, distilled water.
Store the solution in a screwcap Teflon FEP storage bottle
(Sect. 6.2.3).
7.6.2 Antimony solution, stock (1 mL = 1000 /xg Sb) - Dissolve.
0.100 g antimony powder (CASRN 7440-36-0) in 2 mL (1+1)
nitric acid and 0.5 mL cone, hydrochloric acid, heating to
effect solution. Cool, add 20 mL deionized, distilled water
and 0.15 g tartaric acid. Warm the solution to dissolve the
white precipitate. Cool and dilute to 100 mL in volumetric
flask with deionized distilled water. Store the solution in
a screwcap Teflon FEP storage bottle (Sect. 6.2.3).
186
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7.6.3 Arsenic solution, stock (1 ml = 1000 p.g As) - Dissolve
0.1320 g arsenic trioxide (AsA) (CASRN 1327-53-3) in 50 ml
deionized, distilled water ana l ml cone, ammonium hydroxide.
Heat gently to dissolve. Acidify the solution with 2 ml
cone, nitric acid and dilute to 100 ml in a volumetric flask
with deionized, distilled water. Store the solution in a
screwcap Teflon FEP storage bottle (Sect. 6.2.3).
7.6.4 Beryllium solution stock (1 ml = 500 jug Be) - Do not dry.
Dissolve 0.9830 g beryllium sulfate (BeS04«4H20) in
deionized, distilled water, add 1.0 ml cone, nitric acid and
dilute to 100 ml in a volumetric flask with deionized,
distilled water. Store the solution in a screwcap Teflon FEP
storage bottle (Sect. 6.2.3).
7.6.5 Cadmium solution stock (1 ml = 1000 fj.g Cd) - Pickle cadmium
metal in (1+9) nitric acid to an exact weight of 0.100 g.
Dissolve in 4 ml cone, nitric acid, dilute to 100 ml in a
volumetric flask with deionized, distilled water. Store the
solution in a screwcap Teflon FEP storage bottle
(Sect. 6.2.3).
7.6.6 Calcium solution stock (1 ml = 1000 jug Ca) - Suspend
0.2498 g calcium carbonate (CaCOj) dried at 180°C for 1 h
before weighing, in deionized, distilled water). Dissolve
cautiously reacting is vigorous) by adding dropwise 10.0 ml
(1+1) hydrochloric acid and dilute to 100 mL in a volumetric
flask with deionized, distilled water. Store the solution in
a screwcap Teflon FEP storage bottle (Sect. 6.2.3).
7.6.7 Chromium solution, stock (1 ml = 1000 p,g Cr) - Dissolve
0.1923 g chromium trioxide (CrO,) in deionized, distilled
water. When solution is complete, acidify with 1 ml cone.
nitric acid and dilute to 100 ml in a volumetric flask with
deionized, distilled water. Store the solution in a screwcap
Teflon FEP storage bottle (Sect. 6.2.3).
7.6.8 Copper solution, stock (1 ml = 1000 p.g Cu) - Pickle copper
metal in (1+9) nitric acid to an exact weight of 0.100 g.
Dissolve in 2 mL cone, nitric acid. Dilute to 100 ml in a
volumetric flask with deionized, distilled water. Store the
solution in a screwcap Teflon FEP storage bottle
(Sect. 6.2.3).
7.6.9 Iron solution, stock (1 ml = 1000 p.g Fe) - Pickle iron metal
in (1+1) hydrochloric acid to an exact weight of 0.100 g.
Dissolve in 10 ml (1+1) hydrochloric acid. Dilute to 100 ml
in a volumetric flask with deionized, distilled water
(Sect. 7.1). Store the solution in a screwcap Teflon FEP
storage bottle (Sect. 6.2.3).
187
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7.6.10 Lead solution, stock (1 ml = 1000 ^g Pb) - Dissolve 0.1613 g
lead nitrate [Pb(N03)2] in a minimum amount of (1+1) nitric
acid. Add 5 ml cone, nitric acid. Dilute to 100 ml in a
volumetric flask with deionized, distilled water. Store the
solution in screwcap Teflon FEP storage bottle (Sect. 6.2.3).
7.6.11 Magnesium solution, stock (1 ml = 1000 /zg Mg) - Dissolve
0.1658 g magnesium oxide (MgO in 10 mL (1+1) nitric acid,
heating to effect solution. Cool and dilute to 100 ml in a
volumetric flask with deionized, distilled water. Store the
solution in a screwcap Teflon FEP storage bottle
(Sect. 6.2.3).
7.6.12 Nickel solution, stock (1 mL = 1000 p.g Ni) - Dissolve
0.100 g nickel metal in 5 mL hot cone, nitric acid. Cool and
dilute to 100 mL in a volumetric flask with deionized,
distilled water. Store the solution in a screwcap Teflon FEP
storage bottle (Sect. 6.2.3).
7.6.13 Phosphorus solution, stock (1 mL = 1000 ng P) - Dissolve
0.3745 g ammonium phosphate, monobasic [(NH,)H,POJ (CASRN
7722-76-1) in deionized, distilled water and dilute to 100 mL
in a volumetric flask. Store the solution in a screwcap
Teflon FEP storage bottle (Sect. 6.2.3).
7.6.14 Potassium solution, stock (1 mL = 1000 jug K) - Dissolve
0.1907 g potassium chloride (KC1) previously dried at 110°C
for 3 h, in deionized, distilled water, add 2 mL (1+1)
hydrochloric acid and dilute to 100 mL in a volumetric flask.
Store the solution in a screwcap Teflon FEP storage bottle
(Sect. 6.2.3).
7.6.15 Selenium solution, stock (1 mL = 1000 ng Se) - Dissolve
0.1414 g selenium dioxide (Se02) in deionized, distilled
water and dilute to 100 mL in a volumetric flask. Store the
solution in a screwcap Teflon FEP storage bottle
(Sect. 6.2.3).
7.6.16 Sodium solution, stock (1 mL = 1000 ng Na) - Dissolve
0.2542 g sodium chloride (NaCl) in deionized, distilled
water. Add 1.0 mL cone, nitric acid and dilute to 100 mL in
a volumetric flask with deionized, distilled water. Store
the solution in a screwcap Teflon FEP storage bottle
(Sect. 6.2.3).
7.6.17 Thallium solution, stock (1 mL = 1000 p.g Tl) - Dissolve
0.1303 g thallous nitrate (T1N03) in deionized, distilled
water. Add 1.0 mL cone, nitric acid and dilute to 100 mL in
a volumetric flask with deionized, distilled water. Store
the solution in a screwcap Teflon FEP storage bottle
(Sect. 6.2.3).
188
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7.6.18 Zinc solution, stock (1 ml = 1000 M9 Zn) - Pickle zinc metal
in (1+9) nitric acid to an exact weight of 0.100 g. Dissolve
in 5 ml cone, nitric acid. Dilute to 100 ml in a volumetric
flask with deionized, distilled water. Store the solution in
a screwcap Teflon FEP storage bottle (Sect. 6.2.3).
7.7 Prepare four 100 ml primary standard solutions (Sect. 3.11) by
combining aliquots from the appropriate individual stock solutions
(Sect. 7.6) in volumetric flasks and diluting to the mark with
deionized, distilled water. For the wavelength and background
correction positions recommended, prepare the primary standard
solution using the following listed aliquot volumes of the
individual stock standards. Transfer the prepared primary standard
solutions in screwcap Teflon FEP storage bottles (Sect. 6.2.3).
7.7.1 Primary standard solution I (Volume = 100.0 ml)
Analvte
AT
Ca
Cd
Cu
Mg
Sb
Se
Stock
Solution
Aliquot
Vol.. ml
.6.1
.6.6
.6.5
.6.8
7.6.11
7.6.2
7.6.15
7.
7.
7,
7,
10.0
10.0
2.0
1.0
10.0
5.0
5.0
Analyte
Cone..ug/ml
100
100
20
10
100
50
50
7.7.2 Primary standard solution II (Volume = 100.0 ml)
Analvte
As
Cr
Stock
Solution
7.6.3
7.6.7
Aliquot
Vol.. ml
10.0
5.0
Analyte
Cone.. uq/mL
100
50
7.7.3 Primary standard solution III (Volume = 100.0 ml)
Analvte
Na
Pb
Tl
Zn
Stock
Solution
Aliquot
Vol.. ml
7.6.16
7.6.10
7.6.17
7.6.18
10.0
10.0
5.0
5.0
Analyte
Cone., uq/mL
100
100
50
50
189
-------
7.7.4 Primary standard solution IV (Volume = 100.0 ml)
Analvte
Be
Fe
K
Ni
P
Stock
Solution
7.6.4
7.6.9
7.6.14
7.6.12
7.6.13
Aliquot
Vol.. ml
2.0
10.0
20.0
2.0
10.0
Analyte
Cone.. ttg/mL
10
100
200
20
100
7.8 For calibrating the instrument, prepare four CAL solutions
(Sect. 3.12), each in 100-mL volumetric flask by adding 10 ml TMAH
(Sect. 7.4) and 5 ml of cone, nitric acid to 10 mL of each of the
four primary standard solutions (Sect. 7.7) and dilute to the mark
with deionized, distilled water. Transfer the prepared calibration
standards to screwcap Teflon FEP storage bottles (Sect. 6.2.3).
7.8.1 CAL solution I (Volume = 100.0 mL)
Analvte Cone.. ua/mL
Al
Ca
Cd
Cu
Mg
Sb
Se
7.8.2 CAL solution II (Volume
Analvte
As
Cr
10.0
10.0
2.0
1.0
10.0
5.0
5.0
100.0 mL)
Cone.. uq/mL
10.0
5.0
7.8.3 CAL solution III (Volume
Analvte
Na
Pb
Tl
Zn
100.0 mL)
Cone.. ua/mL
10.0
10.0
5.0
5.0
190
-------
7.8.4 CAL solution IV (Volume = 100.0 ml)
Analvte Cone.. ug/ml
Be 1.0
Fe 10.0
K 20.0
Ni 2.0
P 10.0
7.9 Prepare a calibration blank by diluting the combination solution
of 10 ml TMAH (Sect. 7.4) and 5 ml cone, nitric acid to 100 ml in a
volumetric flask with deionized, distilled water. Store the
calibration blank in a screwcap Teflon FEP storage bottle
(Sect. 6.2.4).
7.10 Prepare, a laboratory performance check (LPC) stock solution in a
100-mL volumetric flask by combining the following listed aliquot
volumes of the individual stock standards and diluting to the mark
with deionized, distilled water. Transfer the stock solution to a
screwcap Teflon FEP storage bottle (Sect. 6.2.3).
Stock Aliquot Analyte
Analvte Solution Vol.. ml Cone.. jug/tnL
Al 7.6.1 1.0 10.0
As 7.6.3 1.0 10.0
Be 7.6.4 2.0 10.0
Ca 7.6.6 2.0 20.0
Cd 7.6.5 1.0 10.0
Cr 7.6.7 1.0 10.0
Cu 7.6.8 1.0 10.0
Fe 7.6.9 1.0 10.0
K 7.6.14 10.0 100.0
Mg 7.6.11 2.0 20.0
Na 7.6.16 2.0 20.0
Ni 7.6.12 1.0 10.0
P 7.6.13 10.0 100.0
Pb 7.6.10 1.0 10.0
Sb 7.6.2 1.0 10.0
Se 7.6.15 1.0 10.0
Tl 7.6.17 1.0 10.0
Zn 7.6.18 1.0 10.0
7.10.1 At the time of calibration prepare the LPC in a 100-mL
volumetric flask by adding in the following order, 10 mL TMAH
(Sect. 7.4) and 5 mL cone, nitric acid to 10 mL of the LPC
stock solution (Sect. 7.10) and diluting to the mark with
deionized, distilled water. Transfer the LPC to a screwcap
Teflon FEP storage bottle (Sect. 6.2.3).
191
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Analvte
Al
As
Be
Ca
Cd
Cr
Cu
Fe
K
Mg
Na
Ni
P
Pb
Sb
Se
Tl
Zn
Calibration Check
Std. Cone.. uq/mL
10.0
2.0
2.0
1.0
10.0
1.0
1.0
7.11 Prepare the laboratory fortifying stock solution in a 200-mL
volumetric flask by combining the following listed aliquot volumes
of the individual stock solution and diluting to the mark with
deionized, distilled water. Transfer the laboratory fortifying
stock solution to a screwcap Teflon FEP storage bottle
(Sect. 6.2.3).
Analvte
AL
As
Be
Cd
Cr
Cu
Ni
Pb
Sb
Se
Tl
Zn
Stock
Solution
Aliquot
Vol.. ml
7.6.1
7.6.3
.6.4
.6.5
7.6.7
7.6.8
7.6.12
.6.10
.6.2
.6.15
7.6.17
7.6.18
7.
7.
7.
7.
7.
10.0
10.0
1.0
1.0
2.0
5.0
5.0
5.0
5.0
10.0
5.0
10.0
Analyte
Cone.. uq/mL
50
50
2.5
5
10
25
25
25
25
50
25
50
7.12 Prepare an instrument wash acid solution by diluting 50 mL of cone.
nitric acid to 1 L with deionized, distilled water. Store in a
convenient manner. This solution is to be used to flush the
solution uptake system and nebulizer between standards and samples.
192
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8. SAMPLE COLLECTION. PRESERVATION AND STORAGE
8.1 Fish samples are collected using a variety of equipment, methods
and techniques such as trot lines, trawls, seines, dredges, nets,
ichthyocides and electrofishing. The technique used must be free
from contamination by metals. For example, permanganate may be
used to detoxify Rotenone but should not come in contact with the
fish to be analyzed.6
8.2 Appropriate individual tissue samples should be taken soon after
collection of the fish and must be taken prior to freezing. If
dissection of the tissue cannot be performed immediately after
collection, each fish should be placed in a plastic bag
(Sect. 6.1.5), sealed and placed on ice or refrigerated at
approximately 4°C.
8.3 Prior to dissection, the fish should be rinsed with metal-free
water and blotted dry. Dissection should be performed within 24 h
of collection. Each individual fillet sample should also be rinsed
with metal-free water, blotted dry, placed in a preweighed,
labeled polysulfone centrifuge tube (Sect. 6.2.2) and frozen at
<-20°C (dry ice).
8.4 Skinless fillet samples of approximately 1-2 g (1 cm x 0.5 cm x 2
cm) should be cut from the fish using a special implement (Sect.
4.1) and handled with plastic forceps (Sect. 6.1.2).8'9
8.5 A maximum holding time for frozen samples has not been determined.
9. CALIBRATION AND STANDARDIZATION
9.1 Specific wavelengths and background correction locations given in
Table 1 and instrument operating conditions given in Table 2
should be used whenever possible. However, because of the
difference among various makes and models of spectrometers, the
analyst should follow the instrument manufacturer's instructions
in adapting the instrument's operation to approximate the
recommended operating conditions. Other wavelengths and
background correction locations may be substituted if they can
provide the needed sensitivity and are corrected for spectral
interference.
9.2 Allow the instrument to become thermally stable before beginning.
This usually requires at least 30 min of operation prior to
calibration.
9.3 Optically profile the instrument and adjust the plasma to a
previously established condition by regulating the argon flow rate
through the nebulizer while monitoring the intensity ratio of
selected atom/ion wavelengths [e.g., Cu (I) 324.75 nm/Mn (II) 257.61
nm].
193
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9.4
9.5
Calibrate the instrument according to the instrument manufacturer's
instructions using the prepared calibration blank (Sect. 7.9) and
CAL solutions (Sect. 7.8).
The following operational steps should be used for both CAL
solutions and samples.
9.5.1
to
9.6
Using a peristalic pump introduce the standard or sample
nebulizer at a uniform rate (e.g., 1.2 mL/min."1).
9.5.2 To allow equilibrium to be reached in the plasma, aspirate
the standard or sample solution for 30 sec after
reaching the plasma before beginning integration of the
background corrected signal.
9.5.3 Use the average value of four 4 sec background
corrected integration periods as the atomic emission signal
to be correlated to analyte concentration.
9.5.4 Between each standard or sample, flush the nebulizer and
solution uptake system with the wash acid solution
(Sect. 7.12) for 60 sec or for the required period of time to
ensure that analyte memory effects are not occurring.
Analyze the LPC solution (Sect. 7.10.1) and calibration blank
(Sect. 7.9) immediately following calibration, at the end of the
analyses and periodically throughout the sample run. The analyzed
value of the LPC solution should be within an interval of 95% to
105% of the expected value. If the value is outside the interval,
the instrument should be recalibrated and all samples following the
last acceptable LPC solution should be reanalyzed.
10. QUALITY CONTROL
10.1 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 reagent blanks, fortified blanks and
samples as a continuing check on performance. The laboratory is
required to maintain performance records that define the quality of
data thus generated.
10.2 INITIAL DEMONSTRATION OF PERFORMANCE
10.2.1 Initial demonstration of performance is used to
characterized instrument and laboratory performance,
(method detection limits and quality control verification)
for analyses conducted by this method.
10.2.2 When beginning the use of this method and on a quarterly
basis, verify acceptable laboratory performance with the
preparation and analyses of a quality control sample (QCS)
194
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(Sect. 3.13). The QCS is carried through the entire
analytical operation of the method. If the determined
concentrations are not within ± 5% stated values of
1 mg/L, laboratory performance is unacceptable. The
source of the problem should be identified and corrected
before continuing the analyses.
10.2.3 Method detection limit (MDL) (Sect. 3.2) in M9/9 must be
determined for each of the following analytes: Al, As,
Be, Cd, Cr, Cu, Ni, Pb, Sb, Se, Tl, and Zn. Except for
As, Cu and Zn, the MDLs for all analytes must be
determined in the fish tissue matrix. Because of
background concentrations in fish tissue, MDLs for As, Cu
and Zn should be determined by fortifying and analyzing
the LRB (Sect. 3.5) matrix. The MDL determinations should
be made using seven replicate samples prepared as
described in the procedure (Sect. 11.). The concentration
of the fortified analyte in the sample should be
approximately three times the estimated detection limit.
The determined MDL values tested in Table 1 can be used as
a guide. (Actual solution concentration in jug/mL are 10%
of the listed values). Appropriate dilutions of the
laboratory fortifying stock solution (Sect. 7.11) may be
used to determine MDL.
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.
MDLs should be determined yearly or whenever there is a
significant change in background or instrument response.
10.3 ASSESSING LABORATORY PERFORMANCE - REAGENT AND FORTIFIED BLANKS
10.3.1 A laboratory .reagent blank (LRB) (Sect. 3.5) is to be
analyzed with each group of samples. LRB data are used to
assess contamination from the laboratory environment and
to characterize spectral background from reagents used in
sample processing. Prepare the LRB by transferring 1.0 mL
TMAH (Sect. 7.4) to a clean preweighed, labeled 30-mL
polysulfone Oak Ridge type centrifuge tube (Sect. 6.2.3).
Carry the blank through the entire procedure (Sect. 11) as
a 1.0 g sample ending with a final solution volume of
10 mL. If the value for one or more of the following
195
-------
metals: Al, As, Be, Cd, Cr, Cu, Ni, Pb, Sb, Se, Tl, and Zn
exceeds its determined MDL or established control limits,
then laboratory or reagent contamination should be
suspected and attention should be given to the cleaning
procedure and the purity of the reagents should be
verified. The source of contamination should be corrected
before completing additional analyses.
10.3.2 A field reagent blank (FRB) (Sect. 3.6) that accompanies
each group of samples is to be analyzed in the same manner
as the LRB. Its purpose is to monitor sample collection
and storage condition. Criteria for rejection of analyses
data based on FRB data have not been determined.
10.3.3 A laboratory fortified blank (LFB) (Sect. 3.8) is to be
analyzed with each group of samples. The LFB should
contain the following metals: Al, As, Be, Cd, Cr, Cu, Ni,
Pb, Sb, Se, Tl, and Zn. To prepare the LFB, pi pet 0.1 mL
of the laboratory fortifying stock solution (Sect. 7.11)
into a clean preweighed, labeled 30-mL polysulfone Oak
Ridge type centrifuge tube (Sect. 6.2.2). Add 1 mL of
TMAH (Sect. 7.4) and carry the LFB through the entire
procedure (Sect. 11) as a sample ending with a final
volume of 10 mL. The analyzed values should be within ±
2 standard deviations of an established mean value
determined from seven prior replicate analyses. (Data in
Table 3 may be used as a guide until a sufficient number
of replicates have been determined.) If an analyzed value
is greater than ± 2 standard deviations, it is outside
the warning limits. If it is greater than ± 3 standard
deviations, the analysis is judged to be out of control.
When this is the case, take appropriate steps to identify
and resolve the problems before continuing with the
analyses.
10.4 ASSESSING ANALYTE RECOVERY - LABORATORY FORTIFIED SAMPLE MATRIX
10.4.1 To demonstrate analyte recovery from the tissue matrix
prepare and analyze a laboratory fortified matrix sample
(LFM) (Sect. 3.9) for each type of tissue under analysis.
Select one fish from each group of < 20 samples and at the
time of dissection collect two adjacent fillet or tissue
aliquots of nearly equal size (1 g). To one of the
aliquots add 0.1 mL of the laboratory fortifying stock
solution (Sect. 7.11). Carry both aliquots through the
entire procedure (Sect. 11).
••
10.4.2 Calculate the percent recovery for each analyte, corrected
for background concentrations measured in the unfortified
aliquot, and compare theses values to the control limits
established in Sect. 10.3.3 for the analyses of LFBs.
196
-------
Percent recovery may be calculated in units appropriate to
the matrix, using the following equation:
R = (CF - C) X 100
where, R = percent recovery.
CF = fortified sample concentration
C = sample background concentration
F = concentration equivalent of analyte added
to sample
10.4.3 If the recovery of any analyte in the LFM falls outside
the designated range and the laboratory performance for
that analyte is shown to be in control (Sect. 10.3), the
recovery problem encountered with the fortified sample is
judged to be matrix related, not system related. See
Sect. 13.4 and Table 5 for typical recovery data.
11. PROCEDURE
11.1 At the start of sample processing, remove the cap from the
preweighed, labeled centrifuge tube (Sect. 6.2.2) containing the
sample and reweigh the tube to determine the weight of the tissue
by difference. This can be done using the analytical balance
(Sect. 6.3.5). Wipe the outside of the centrifuge tube with a
Kimwipe or suitable paper tissue and place the tube horizontally
on the pan. The weight of the tissue should be between 1 and 2 g
and expressed to the nearest 10 mg. Record the tissue weight.
11.2 Using a 2-mL graduated pipet or an air displacement pipetter
(Sect. 6.3.1), add a volume of 25% tetramethylammonium hydroxide
(TMAH) (Sect. 7.4) equal to the weight of the tissue (1 ml TMAH =
1 g tissue). The aliquot of TMAH should be to the nearest tenth of
a milliliter equal to the tissue weight (e.g., 1.6 ml of TMAH for
1.62 g of tissue). With the TMAH added, replace and tighten the
cap securely. (This will minimize the odor caused in heating the
sample mixture.) Place the sample in an open rack for adequate
heating and place the rack in a drying oven preheated to 65°C ±
5°C and warm the sample for 1 h.
11.3 After an hour of heating, remove the sample from the oven,
retighten the cap if loose, and mix the sample for a few seconds
using a vortex mixer (Sect. 6.3.6) set at medium power setting.
Return the sample to the drying oven and heat for an additional
hour.
11.4 After the second hour of heating, again vortex mix the sample and
allow the capped sample to stand overnight at room temperature.
197
-------
11.5
11.6
11.7
11.8
The following morning, acidify the sample with cone, nitric acid
(Sect. 7.2) to between 4% and 5% (v/v) acid. The volume of nitric
acid added to each sample is based on the final volume of sample.
The final sample volume is calculated by multiplying the wet tissue
weight by 10. Using a 1-mL graduated pipet or an air displacement
pipetter (Sect. 6.3.1), add the appropriate volume of nitric acid
as indicated in the following table:
Weight of
Tissue, a
Final Sample
Volume. mL
0.80
1.05
1.25
1.45
1.65
1.85
2.05
- 1.04
- 1.24
- 1.44
- 1.64
- 1.84
- 2.04
- 2.24
8 to
10 to
12 to
14 to
10
12
14
16
16 to 18
18 to 20
20 to 22
Volume of
Cone. HN03 Added, ml
0.4
0.5
0.6
0.7
0.8
0.9
1.0
After the acid addition, recap the tube and lightly vortex mix the
sample. Place the tube to the drying oven preheated to 100°C and
heat the sample for an hour to solubilize the metals before
proceeding. Note: After the acid is added,' solids will fall out
of solution and a precipitate will form. This is normal and to be
expected.
After the period of solubilization, cool the tube to room
temperature. Uncap the tube and place the tube on the single pan
balance (Sect. 6.3.4) in a tared 100-mL Griffin beaker. Adjust the
final volume of the sample by adding deionized, distilled water
from a "squeeze" wash bottle (Sect. 6.2.4) while weighing the tube
to an appropriate weight to maintain the constant weight/volume
ratio of 1 g/10 ml. The appropriate weight is calculated by
multiplying the wet tissue weight by 10 and adding the product to
the recorded weight of the empty tube.
After dilution is completed, recap the tube and vortex mix the
sample. After mixing, centrifuge (Sect. 6.3.7) the sample at 2000
rpm. for 10 min. After centrifuging, the sample may contain
floatable solids as a surface layer as well as the precipitate.
Also, some particles may adhere to the wall of the tube. This
condition is normal and should not cause concern unless the
analysis solution actually contains suspended material. The sample
is now ready for analysis. Analyze the sample within 24 h of
preparation (Sect. See 4.2).
Aspirate the sample into the ICP using the same operating
conditions used in calibration (Sect. 9) while making certain the
precipitate is not disturbed and inadvertently aspirated. If the
surface of the analysis solution is partially covered with
floatable solids, proceed by removing the tip of the aspiration
tube from the wash solution (Sect. 7.12) and allow an air bubble
198
-------
segment to form in the sample uptake line. Reverse the pump flow
and, while back pumping the air bubble, insert the aspiration tube
past the floatable solids into the sample solution. Change the
pump flow back to uptake direction and aspirate the sample.
12. CALCULATIONS
12.1 If dilutions are performed, the appropriate factor must be
applied to sample values.
12.2 Data read from the instrument in /zg/mL should be rounded to the
thousandth place.
12.3 Subtract the LFB where appropriate (Sect. 4.4).
12.4 To express the data in concentrations of jug/9 wet tissue weight
multiply the rounded net ng/ml data by a factor of 10.
12.5 Report jug/g wet tissue weight data up to three significant
figures.
12.6 Do not report data below the determined MDL.
13. PRECISION AND ACCURACY
13.1 The precision and recovery data presented in this method are single
laboratory verification data only. The data were collected
utilizing the recommended instrument conditions described in the
method.
13.2 The precision and recovery data presented in Table 3 are for the
LFB concentrations recommended in this method. The data can be
used as a guide for quality control limits (Sect. 10.3) until the
time the method user establishes actual limits.
13.3 The comparative data for the four types of fish fillets (bluegill,
catfish, salmon, and tuna) presented in Table 4 are for
verification of version 2.0 of this method. In addition to version
2.0, data are included for the former version 1.3 of this method,
which incorporated the use of 50% hydrogen peroxide and a vigorous
acid digestion procedure that utilizes nitric acid and hydrogen
. peroxide with the digestate finally being diluted in 5% (v/v)
hydrochloric acid. The analytes listed are those naturally
occurring elements in fish tissue plus Ni found in the salmon and
the Cd and Se found in the tuna. The purpose of the comparison is
to demonstrate the effectiveness and usefulness of the TMAH
solubilization. For each type of fish all fillets were taken from
the same fish. Except as noted in the table, Method 200.11 mean
data for the analytes: As, Cd, Cu, Ni, Se and In are from the
analyses of four replicate fillets while the mean data for Ca, Fe,
K, Mg, Na and P are from the analyses of eight replicate fillets.
199
-------
The acid digestion mean data for all analytes are from the analyses
of four replicate fillets. The catfish, salmon and tuna data for
version 2.0 of Method 200.11 were statistically compared to version
1.3 data and the acid digestion data. The comparison was made
using a two tail Student's t test at alpha level 0.05. If a
statistical difference was determined, the data were tested for
practical difference by determining the relative percent difference
between the two means. If the relative percent difference was 10%
or less, it was concluded that there is no practical difference
between the methods. Listed in Sect. 13.3.1 are the relative
percent differences for version 1.3 data and in Sect. 13.3.2 the
relative percent differences for the acid digestion data for those
analytes where a statistical difference was proven. The large
difference for the salmon data between version 2.0 and 1.3 cannot
be explained. At present, the differences are attributed to the
individual fish used in the comparison. This was concluded from
analyses of other fillet segments from the same fish that indicated
good agreement between the two versions but gave extremely elevated
concentrations for Cu - 3 /jg/g, Fe - 18 /zg/g and Zn - 8 /zg/g.
13.3.1 RELATIVE PERCENT DIFFERENCES - VERSION 1.3
ANALYTE
Fe
K
Mg
Na
P
P
Zn
FISH TISSUE
Salmon
Salmon
Salmon
Salmon
Salmon
Tuna
Salmon
RELATIVE DIFFERENCE
37%
21%
18%
30%
14%
6%
19%
13.3.2 RELATIVE PERCENT DIFFERENCES - ACID DIGESTION
ANALYTE
As
As
Cu
K
Mg
Na
P
P
FISH TISSUE
Catfish
Salmon
Catfish
Tuna
Tuna
Salmon
Catfish
Tuna
RELATIVE DIFFERENCE
50%
82%
12%
11%
10%
27%
6%
14%
13.4 The precision and recovery data for the four types of fish fillets
(bluegill, catfish, salmon, and tuna) presented in Table 5 are from
the analyses of four replicate LFMs taken from the same fish and
fortified with the same concentrations as the LFB replicates listed
in Table 3. Sample concentration subtracted before calculation of
percent recovered were mean values taken from Table 4. Except for
200
-------
Sb, which shows consistently low recovery, all other analytes have
recoveries that range from 90 to 112% with an average of 101% and
RSD values that range from 0.7 to 10.7% with an average of 3.7%,
only slightly higher than the LFB average of 3.1% calculated from
Table 3 values.
13.5 Table 6 lists the mean, standard deviation, relative standard
deviation, and percent recovery data from the analysis of four,
0.25 g aliquots of dried NBS SRM 1566 Oyster Tissue. Data from the
analyses of reference material are included for support of the
procedure. Except for Cr and Fe, all recovery data are between 90
and 110%.
14. REFERENCES
1. Code of Federal Regulations 40, Ch. 1, Pt. 136 Appendix B.
2. Gross, S. B., and E. S. Parkinson, "Analyses of Metals in Human
Tissues Using Base (TMAH) Digests and Graphite Furnace Atomic
Absorption Spectrophotometry," Atomic Absorption Newsletter. Vol. 13,
No. 4, pp. 107-108, 1974.
3. Murthy, L., E. E. Menden, P. M. Eller, and H. G. Petering, "Atomic
Absorption Determination of Zinc, Copper, Cadmium and Lead in Tissues
Solubilized by Aqueous Tetramethylammonium Hydroxide," Analytical
Biochemistry. Vol. 53, pp. 365-372, 1973.
4. Versieck, J., and F. Barbier, "Sample Contamination as A Source of
Error in Trace-Element Analysis of Biological Samples," Talanta.
Vol. 29, pp. 973-984, 1982.
5. Annual Book of ASTM Standards, Volume 11.01, American Society for
Testing and Materials, 1916 Race St., Philadelphia, Pennsylvania,
19103.
6. Standard Methods for the Examination of Mater and Wastewater. 16th
Edition, 1985. Part 1006; "Fish: Sample Collection and Preservation."
7. Ney, J. J., and M. G. Martin, "Influences of Prefreezing on Heavy
Metal Concentrations in Bluegill Sunfish," Water Res.. Vol. 19, No. 7,
pp. 905-907, 1985.
8. "The Pilot National Environmental Specimen Bank," NBS Special
Publication 656, U. S. Department of Commerce, August, 1983.
9. Koirtyohann, S. R., and H. C. Hopps, "Sample Selection, Collection,
Preservation and Storage for Data Bank on Trace Elements in Human
Tissue," Federation Proceedings, Vol. 40, No. 8, June, 1981.
10. Method 200.11, "Determination of Metals in Fish Tissue by Inductively
Coupled Plasma-Atomic Emission Spectrometry," Revision 1.3, April 1987.
U.S. Environmental Protection Agency, Office of Research and
Development, Environmental Monitoring and Support Laboratory,
Cincinnati, Ohio 45268.
201
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TABLE 1. RECOMMENDED WAVELENGTHS WITH LOCATIONS
FOR BACKGROUND CORRECTION AND METHOD DETECTION LIMITS (MDL)
Analyte Wavelength,
nm
Location for
Bkgd. Correction
MDL, /xg/g
Wet Tissue Weight
(1)
(*)
AT
As
Be
Ca
Cd
Cr
Cu
Fe
K
Mg
Na
Ni
P
Pb
Sb
Se
Tl
Zn
Wavelength X 2
HDL determined
308.215
193.696
313.042
315.887
226.502
205.552
324.754
259.940
766.491
279.079
588.995
231.604
214.914
220.353
206.883
196.026
190.864
213.856
+ 0.061 nm
+ 0.061 nm
- 0.061 nm
+ 0.061 nm
+ 0.061 nm
X 2 - 0.030 nm
- 0.061 nm
+ 0.061 nm
- 0.061 nm
- 0.061 nm
+ 0.061 nm
X 2 - 0.030 nm
X 2 + 0.030 nm
+ 0.061 nm
+ 0.061 nm
- 0.061 nm
+ 0.061 nm
X 2 + 0.030 nm
indicates wavelength is read in
in LRB matrix.
0.3
0.4*
0.02
0.02
0.05
0.05*
0.08
0.2
0.2
0.6
0.5
0.07*
second order.
202
-------
TABLE 2. INDUCTIVELY COUPLED PLASMA INSTRUMENT OPERATING CONDITIONS
Forward rf power
Reflected rf power
Viewing height above
work coil
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
16 mm
Liquid argon
40 psi
19 L/min
630 mL/min
300 mL/min
1.2 mL/min
203
-------
TABLE 3. PRECISION AND RECOVERY OF DATA LABORATORY FORTIFIED BLANK
Concentration, /*g/g
Analyte
Al
As
Be
Cd
Cr
Cu
Ni
Pb
Sb
Se
Tl
Zn
Theo
Value
5.00
5.00
0.25
0.50
1.00
2.50
2.50
2.50
2.50
5.00
2.50
5.00
Analysis
Mean (1)
4.94
5.11
0.26
0.52
1.02
2.57
2.55
2.51
2.42
5.05
2.48
5.01
Std
Dev
0.14
0.13
0.01
0.01
0.04
0.07
0.08
0.09
0.22
0.16
0.09
0.13
RSD
2.8%
2.5%
3.7%
1.9%
3.9%
2.7%
3.1%
3.6%
9.1%
3.2%
3.6%
2.6%
Percent
Recovered
99%
102%
104%
104%
102%
103%
102%
100%
97%
101%
99%
100%
(1) Data from seven replicate determinations
204
-------
TABLE 4. COMPARATIVE METHODS DATA
Concentration, M9/9 Wet Tissue Weight
Fish Tissue - Blueaill Fillet
Analyte
As
Ca
Cu
Fe
K
Mg
Na
P
Zn
(1) Data from
Fish Tissue -
Analyte
As
Ca
Cu
Fe
K
Mg
Na
P
Zn
Method 200.11
Version 2.0 Version 1.3
Mean Std Dev Mean (1) Std Dev
1.08
141
0.18
1.57
4690
346
216
2640
4.74
duplicate
0.13
37
0.03
0.18
300
23
36
200
0.07
analyses
1.03
131
0.15
1.48
4870
370
247
2700
4.88
, standard
_«.
—
—
—
—
— —
—
—
— —
deviations
Acid Digestion
HNO,/H,0,
Mean (1) Std Dev
0.39
134
0.22
1.69
4140
340
235
2370
4.77
not provided
Catfish Fillet
Version
Mean
0.45
110
0.33
2.01
3400
244
460
1840
5.68
Method
2.0
Std Dev
0.10
5
0.09
0.30
240
16
17
90
0.58
200.11
Acid Digestion
Version 1.3
Mean Std Dev
0.47
111
0.35
1.95
3260
238
464
1750
6.02
0.14
15
0.10
0.23
370
38
19
200
1.07
HN03/H_2°2
Mean Sid Dev
0.20 0.
123
0.31 0.
2.38 0.
3640
230
467
1950
5.67 1.
06
2
01
53
70
7
6
30
68
205
-------
TABLE 4. COMPARATIVE METHODS DATA (Continued)
Concentration, /zg/g Wet Tissue Weight
Fish Tissue - Salmon Fillet
Analyte
As
Ca
Cu
Fe
K
Mg
Na
Ni
P
Zn
Version
Mean
0.79
118
0.70
3.12
3160
233
653
0.09
2090
4.37
Method
2.0
Std Dev
0.03
14
0.05
0.55
180
10
64
0.04
100
0.40
200.11
Version
Mean
0.84
98
0.69
2.15
280
280
481
0.07*
2410
3.60
1.3
Std Dev
0.13
28
0.06
0.25
90
7
22
0.04
90
0.30
Acid
HP
Mean
0.41
114
0.57
3.16
3110
229
496
0.07
2000
3.72
Digestion
JO /H 0
ttd Dev
0.07
27
0.13
0.48
360
27
66
0.03
160
0.46
*Data below MDL, normally not reported - listed only for comparison
Fish Tissue - Tuna Fillet
Analyte
As
Ca
Cd
Cu
Fe
K
Mg
Na
P
Se
Zn
/•n M n ~
Method 200.11
Version 2.0 Version 1.3
Mean Std Dev Mean Std Dev
3.01
33.4
0.020
0.23
6.14
4640
384
328
3060
0.95
3.12
0.45
3.7
0.006
0.10
1.51
110
8
35
50
0.22
0.24
3.29
37.0
0.020
0.22
5.15
4530
373
360
2890
0.73
2.83
0.15
6.5
0.006
0.04
1.01
160
13
34
80
0.05
0.09
Acid Digestion
HN03/H202
Mean(l) SW Dev
2.83
37.8
0.025
0.11
7.33
4140
347
342
2670
N.DxO.8
2.90
0.39
7.8
0.003
0.04
1.08
120
10
J. V
39
90
0.23
206
-------
TABLE 5. PRECISION AND RECOVERY DATA
Concentration, M9/9 Wet Tissue Weight
Fish Tissue - Blueaill Fillet
Analyte
Al
As
Be
Cd
Cr
Cu
Ni
Pb
Sb
Se
Tl
Zn
*Data below
Fish Tissue
AnaTyte
Al
As
Be
Cd
Cr
Cu
Ni
Pb
Sb
Se
Tl
Zn
Sample Cone.
Cone. Added
1.08
-
0.18
-
0.54*
4.74
MDL, reported
5.00
5.00
0.25
0,50
1.00
2.50
2.50
2.50
2.50
5.00
2.50
5.00
for exp
Analysis
Mean
5.06
6.41
0.28
0.52
1.03
2.74
2.65
2.57
2.27
5.58
2.56
9.77
lanation of
Std
Dev
0.15
0.32
0.012
0.018
0.03
0.10
0.10
0.19
0.15
0.19
0.07
0.45
elevated If I
RSD
3.0%
5.0%
4.3%
3.5%
2.9%
3.6%
3.8%
7.4%
6.6%
3.4%
2.7%
4.6%
1
Percent
Recovery
101%
107%
112%
104%
103%
102%
106%
103%
91%
112%
102%
101%
-Catfish Fillet
Sampl e
Cone.
0.45
0.33
-
-
5.68
Cone.
Added
5.00
5.00
0.25
0.50
1.00
2.50
2.50
2.50
2.50
5.00
2.50
5.00
Analysis
Mean
4.94
5.50
0.26
0.49
0.98
2.85
2.42
2.43
2.09
4.60
2.43
11.0
Std
Dev
0.16
0.07
0.005
0.008
0.02
0.04
0.10
0.10
0.07
0.40
0.16
1.18
RSD
3.2%
1.3%
1.9%
1.6%
2.0%
1.4%
4.1%
4.1%
3.3%
8.7%,
6.6%
10.7%
Percent
Recovery
99%
101%
104%
98%
98%
101%
97%
97%
84%
92%
97%
106%
207
-------
TABLE 5. PRECISION AND RECOVERY DATA (Continued)
Concentration, /zg/g Wet Tissue Weight
Fish Tissue - Salmon F^i^t
Analyte
Al
As
Be
Cd
Cr
Cu
Ni
Pb
Sb
Se
Tl
Zn
Fish Tissue
Analyte
Al
As
Be
Cd
Cr
Cu
Ni
Pb
Sb
Se
Tl
Zn
Sample
Cone.
0.79
0.70
0.09
4.37
- Tuna Fillet
Sample
Cone.
3.01
0.02
0.23
-
0.95
3.12
Cone.
Added
5.00
5.00
0.25
0.50
1.00
2.50
2.50
2.50
2.50
5.00
2.50
5.00
Cone.
Added
5.00
5.00
0.25
0.50
1.00
2.50
2.50
2.50
2.50
5.00
2.50
5.00
Analysis
Mean
4.67
5.59
0.25
0.47
0.93
3.20
2.41
2.38
2.01
5.05
2.36
8.85
Analysis
Mean
5.09
8.29
0.28
0.54
0.99
2.74
2.56
2.57
2.00
6.33
2.70
7.99
Std
Dev
0.23
0.13
0.002
0.015
0.03
0.12
0.11
0.09
0.15
0.28
0.90
0.62
Std
Dev
0.60
0.53
0.003
0.024
0.01
0.02
0.06
0.08
0.11
0.27
0.13
0.20
RSD
4.9%
2.3%
0.8%
3.2%
3.2%
3.8%
4.6%
3.8%
7.4%
5.5%
3.8%
7.0%
RSD
1.2%
6.4%
1.1%
4.4%
1.0%
0.7%
2.3%
3.1%
5.5%
4.3%
3.7%
2.5%
Percent
Recovery
93%
96%
100%
94%
93%
100%
93%
95%
80%
101%
94%
90%
Percent
Recovery
102%
106%
112%
104%
99%
100%
102%
103%
80%
108%
108%
97%
208
-------
TABLE 6. ANALYSES DATA - NBS SRM 1566 OYSTER TISSUE
Concentration, /Ltg/g Dry Weight
Analyte
As
Ca
Cd
Cr
Cu
Fe
K
Mg
Na
Ni
P
Pb
Se
Zn
Certified
Value
13.4 ± 1.9
1500 ± 200
3.5 ±0.4
0.69 ± 0.27
63.0 ± 3.5
195 ± 34
9690 ± 50
1280 ± 90
5100 ± 300
', 1.03 ± 0.19
8100*
0.48 ± 0.04
2.1 ± 0.5
852 ± 14
Analysis
Mean (1)
14.6
1560
3.39
N.DxO.02
63.0
128
9860
1270
4790
1.28
7360
N.DX0.8
N.D.<2.4
832
Std
Dev
0.2
80
0.05
-
1.5
16
50
30
110
0.41
180
-
- -
5
RSD
1.5%
5.1%
1.5%
-
2.4%
13%
0.5%
2.4%
2.3%
32%
2.4%
-
-
0.6%
Percent
Recovered
109%
104%
97%
-
100%
66%
102%
99%
94% .
124%
94%
'.';
-
98%
(1) N.D. - Not detected below MDL
*Phosphorus value not certified
209
-------
-------
METHOD 218.6
DETERMINATION OF DISSOLVED HEXAVALENT CHROMIUM
IN DRINKING WATER, GROUNDWATER, AND INDUSTRIAL WASTEWATER
EFFLUENTS BY ION CHROMATOGRAPHY
Elizabeth J. Arar, Stephen E. Long
Technology Applications, Inc.
and
John D. Pfaff
Inorganic Chemistry Branch
Chemistry Research Division
Revision 3.2
April 1991
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
211
-------
METHOD 218.6
™uJERMINATION OF DISSOLVED HEXAVALENT CHROMIUM IN DRINKING WATER,
GROUNDWATER, AND INDUSTRIAL WASTEWATER EFFLUENTS BY ION CHROMATOGRAPHY
SCOPE AND APPLICATION
1.1
1.2
1.3
1.4
This method provides procedures for determination of dissolved
nexavalent chromium in drinking water, groundwater, and industrial
wastewater effluents.
The method detection limits (MDL, defined in Sect. 3) for 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.
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.
This method should be used by analysts experienced in the use of ion
chromatography and the interpretation of ion chromatograms.
2. SUMMARY OF METHOD
2.1 An aqueous sample is filtered through a 0.45-/im filter and the
filtrate is adjusted to a pH of 9 to 9.5 with a buffer solution A
measured volume of the sample (50-250 /zL) is introduced into the ion
cnromatograph. A guard column removes organics from the sample
before the Cr(VI) as CrO^' is separated on an 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. DEFINITIONS
3.1 DISSOLVED - Material that will pass through a 0.45 urn membrane
filter.
3.2
3.3
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- it
is determined from data produced by analyzing a sample in a qiven
matrix containing analyte1.
LINEAR DYNAMIC RANGE - The concentration range over which the
analytical working curve remains linear.
212
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3 4 LABORATORY REAGENT BLANK (LRB) - An aliquot of reagent water that is
treated exactly like a sample including exposure to all glassware,
equipment, solvents, and reagents that are used with.samples, me
LRB is used to determine if the method analyte is present in the
laboratory environment, reagents, or apparatus.
3 5 STOCK STANDARD SOLUTION - A concentrated, certified standard
solution of the method analyte. The stock standard solution is used
to prepare calibration standards.
3.6 CALIBRATION STANDARD (CAL) - A solution prepared from the stock
standard and used to calibrate the instrument response with respect
to analyte concentration.
3.7 LABORATORY FORTIFIED BLANK (LFB) - An aliquot of reagent water to
which a known quantity of method analyte is added in the laboratory.
The LFB is analyzed exactly like a sample, and its purpose is to
determine whether the method is within accepted control limits.
3.8 LABORATORY FORTIFIED SAMPLE MATRIX (LFM) - An aliquot of an
environmental sample to which a known quantity of 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 result. 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 the concentration found.
3.9 QUALITY CONTROL SAMPLE (QCS) - A solution containing a known
concentration of analyte prepared by a laboratory other than the
laboratory performing the analysis. The sample is used to check
laboratory performance.
3 10 LABORATORY DUPLICATES (LD) - Two aliquots of the same sample that
are treated exactly the same throughout preparative and .analytical
procedures. Analyses of laboratory duplicates indicate precision
associated with laboratory procedures.
3 11 LABORATORY PERFORMANCE CHECK STANDARDS (LPC) - A solution of the
analyte prepared in the laboratory by making appropriate dilutions
of the stock standard in reagent water. The LPC is used to evaluate
the performance of the instrument system within a given calibration
curve.
4. 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,
213
-------
4.1.2
4.1.3
4.1.4
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.
Oxidation of soluble Cr(III) to Cr(VI) can occur in an
alkaline medium in the presence of oxidants such as
Fe(III) and oxidized Mn or as a result of the aeration
that occurs in most extraction procedures2"5.
Reduction of Cr(VI) to Cr(III) can occur in the presence
of reducing species in an acidic medium. At a pH of 6 5
or greater, however, HCrO" is converted to CrO/'which is
less reactive than the HCr04'. 4
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 chloride6. Poor
recoveries from fortified samples and tailing peaks are
typical manifestations of column overload.
5. SAFETY
6.
oH c^°miUm 1S ^OX1C and a susPfcted carcinogen and should
5 Tth aPP™Pnate precautions3'4. Extreme care should be
cd Wce", w?19hinf the salt for preparation of the stock
standard. Each laboratory is responsible for maintaining a current
rhpS6iSS flle-^ SS?A Ration* regarding the safe having of
s^tv aiftfP ehlfied ^ this., method. A reference file of material
safety data sheets should also be available to all personnel
involved in the chemical analysis7-8. p^onnei
APPARATUS AND EQUIPMENT
6.1 ION CHROMATOGRAPH
6.1.1
6.1.2
6.1.3
6.1.4
6.1.5
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!
Helium gas supply (High purity, 99.995%).
Pressurized eluent container, plastic, 1- or 2-L size.
Sample loops of various sizes (50-2500L).
A pressurized reagent delivery module with a mixing tee
and beaded mixing coil.
214
-------
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 resolving Cr04 " 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 volumetric flasks and a graduated
cylinder.
6.2.2 Assorted Class A calibrated pipettes.
6.2.3 10-mL male luer-lock disposable syringes.
6.2.4 0.45-/wn syringe filters.
6.2.5 Storage bottle - High density polyproplene, 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-/um filter discs, 7.3-cm diameter (Gelman Aero 50A,
Mfr. No. 4262 or equivalent).
215
-------
6.3.5 Plastic syringe filtration unit (Baxter Scientific, Cat.
No. 1240 IN or equivalent).
7. REAGENTS AND CONSUMABLE MATERIALS
7.1 REAGENTS - All chemicals are ACS grade unless otherwise indicated.
7.1.1
7.1.2
7.1.3
7.1.4
7.1.5
Ammonium hydroxide, NH,OH, (sp.gr. 0.902),
(CASRN 1336-21-6). '
Ammonium sulphate, (NH4)2S04, (CASRN 7783-20-2).
1,5-Diphenylcarbazide, (CASRN 140-22-7).
Methanol, HPLC grade.
Sulfuric acid, concentrated (sp.gr. 1.84).
7.2 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. 3
7.3 Cr(VI) STOCK SOLUTION - Dissolve 4.501 g of Na2CrO,'4H20 in ASTM
Type I water and dilute to 1 L. Transfer to a polypropylene storaqe
container. b
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 /tg/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.
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
216
-------
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. 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-/«n 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 should be analyzed within 24 h of
collection.
9. CALIBRATION
9.1 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.
9.1.1 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 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.
9.1.2 Injection loop size is chosen based on standard and sample
concentrations and the selected attenuator setting. A
250-/iL loop was used to establish the method detection
limits in Table 1. A 50-jiL loop is normally sufficient
for higher concentrations. The sample volume used to load
the injection loop should be at least 10 times the loop
217
-------
9.1.3
9.2
size so that all tubing in contact with sample is
thoroughly flushed with new sample to prevent cross-
contamination.
A calibration curve of analyte response (peak height or
area) versus analyte concentration should be constructed.
IhL«oefflc1ent of correlation for the curve should be
0.999 or greater.
PE?™RMANCE - Check the performance of the instrument and
it "^^ation using data gathered from analyses of
laboratory blanks, calibration standards, and a QCS.
9.2.1
9.2.2
After the calibration has been established, it should be
TI ire y analyzi?2 a QCS (7'6>- If the measured value
of a QCS exceeds ± 10% of the established value, a second
analysis should be performed. If the value still exceeds
the established value, the analysis should be terminated
until the source of the problem is identified and
corrected.
To verify that the instrument is properly calibrated on a
continuing basis, run a LRB and a LPC after every ten
analyses. The results of analyses of standards will
indicate whether the calibration remains valid. If the
measured concentration of the analyte deviates from the
true concentration by more than ±5%, the instrument must
be recalibrated and the previous ten samples reanalyzed
The instrument response from the calibration check may be
used for recall oration purposes.
10. QUALITY CQNTROI
10.1 Each laboratory using this method is required to operate a formal
Troalll rnntr°J (?C) "W™: The minim requireLti of this
program consist of an initial demonstration of laboratory
hi3"? the analy?1s of laboratory reagent blanks, and
n ?lank- and samples as a c°ntinuing check on performance.
«ab?£atorVf reSu1£ed to maintain performance records that
define the quality of the data thus generated.
10.2 INITIAL DEMONSTRATION OF PERFORMANCE
The initial demonstration of performance is used to
characterize instrument performance (MDLs and linear
calibration range) for analyses conducted by this method.
A MDL should be established using reagent water fortified
at a concentration of two-five times the estimated
S^T 1i"1t\ T°.dejerm1ne the MDL value, take seven
replicate aliquots of the fortified reagent water and
process through the entire analytical method. Perform all
218
10.2.1
10.2.2
-------
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 = 3.143 for seven replicates].
s = standard deviation of the replicate analyses.
10.2.3 Linear dynamic range - Linear dynamic ranges are governed
by Beer's Law. A set of at least five standards covering
the estimated linear range should be prepared fresh from
the stock solution and one analysis of each performed. A
log vs. log plot of peak height vs. analyte concentration
having a slope between 0.98 and 1.02 will indicate
linearity (7). The linear dynamic range for this method
covered four orders of magnitude (1 /zg/L to 10,000 /*g/L)
when peak height was used.
10.3 ASSESSING LABORATORY PERFORMANCE - REAGENT AND FORTIFIED BLANKS
10.3.1 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 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.
10.3.2 The laboratory must analyze at least one LFB (Sect. 7.5)
with each set of samples. Calculate accuracy as percent
recovery (Sect. 10.4.2). If the recovery of Cr(VI) falls
outside the control limits (Sect. 10.3.3), then the
procedure is judged out of control, and the source of the
problem should be identified and resolved before
continuing the analysis.
10.3.3 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
219
-------
10.4 ASSESSING ANALYTE RECOVERY - LABORATORY FORTIFIED SAMPLE MATRIX
10.4.1
10.4.2
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).
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. 10.3.3 for the analysis of LFBs.
Fortified recovery calculations are not required if the
fortified concentration is less than 10% of the sample
background concentration. Percent recovery may be
calculated in units appropriate to the matrix, using the
following equation:
R = CF -
C X 100
10.4.3
where:
R = percent recovery.-
CF= fortified sample concentration.
C - sample background concentration.
F = concentration equivalent of Cr(VI) added to sample.
If the recovery of Cr(VI) falls outside control limits,
while the recovery obtained for the LFB was shown to be in
control (Sect. 10.3), 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 matrix1.
10.5 QUALITY CONTROL SAMPLE (QCS) - Each quarter, the laboratory should
analyze one or more QCS (if available). If criteria provided with
the QCS are not met, corrective action should be taken and
documented.
11. PROCEDURE
11.1 SAMPLE PREPARATION
Filtered, pH adjusted samples at 4°C should be brought to ambient
temperature prior to analysis.
11.2 Initiate instrument operating configuration and calibrate (Sect. 9).
11.3 Draw into a new, unused syringe (Sect. 6.2.3) approximately 3 mL of
sample and attach a syringe filter to the syringe. Discard 0.5 mL
through the filter and load 10X the sample loop volume. Samples
220
-------
having concentrations higher than the established linear dynamic
range should be diluted into the calibration range.and reanalyzed.
12. CALCULATIONS
12.1 From the calibration curve the concentration of the sample can be
determined. Report values in ng/L. Data should be corrected if any
dilution of the sample occured. Data should be corrected for any
Cr(VI) contamination found in reagent blanks.
12.2 The QC data obtained during sample analyses provide an indication of
the quality of sample data and should be provided with sample
results.
13. PRECISION AND ACCURACY
13.1 Instrument operating conditions used for single-laboratory testing
of the method are summarized in Table 2. Dissolved Cr(VI) MDLs
(Sect. 10.2.2) are listed in Table 1.
13.2 Data obtained from single-laboratory testing of the method are
summarized in Table 3 for five water samples representing drinking
water, deionized water, groundwater, treated municipal sewage
wastewater, and treated electroplating wastewater. Samples were
fortified with 100 and 1000 fig/I of Or(VI) and recoveries determined
(Sect. 10.4.2).
14. REFERENCES
1. Glaser,*J.A., Foerst, D.L., McKee, 6.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. Bartlett, R. and James, B., "Behavior of Chromium in Soils: III.
Oxidation", J. Environ. Qua!.. Vol.8, No.l, 1979, pp.31-35.
3. Zatka, V.J., "Speciation of Hexavalent Chromium in Welding Fumes
Interference by Air Oxidation of Chromium", Am. Ind. Hvg. Assoc. J.,
Vol.46, No.7, 1985, pp.327-331.
4. Pedersen, B., Thomsen, E. and Stern, R.M., "Some Problems in
Sampling, Analysis and Evaluation of Welding Fumes Containing
Cr(VI)", Ann. Occup. Hvg.. Vol.31, No.3, 1987, pp. 325-338.
5. Messman, J.D., Churchwell, M.E., et.al. Determination of Stable
Valence States of Chromium in Aqueous and Solid Waste Matrices-
Experimental Verification of Chemical Behavior. EPA/600/S4-86/039,
U.S. Environmental Protection Agency, Cincinnati, Ohio, 1987, 112pp.
6. Dionex Technical Note No. 26, May 1990.
221
-------
7.
8.
"Proposed OSHA Safety and Health Standards, Laboratories,"
Occupational Safety and Health Administration, Federal Register,
July 24, 1986.
"OSHA Safety and Health Standards, General Industry," (29 CFR 1910),
Occupational Safety and Health Administration, OSHA 2206, revised
January 1976.
9. Johnson, D.C., Anal. Chim. Acta, Vol. 204, No.l, 1988.
222
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TABLE 1. METHOD DETECTION LIMIT FOR CR(VI)
Matrix Type
Cone. Used to Compute MDL
uq/L
MDL (a)
ug/L
Reagent Water
Drinking Water
Ground Water
Primary Sewage
wastewater
Electroplating
wastewater
1
2
2
2
0.4
0.3
0.3
0.3
0.3
(a) MDL concentrations are computed for final analysis concentration
(Sect. 10.2).
223
-------
TABLE 2. ION CHROMATOGRAPH1C CONDITIONS
Columns: Guard Column - Dionex lonPac NG1
Separator Column - Dionex lonPac AS7
Eluent: 250 mM (NH,),SO,
100 mM NH,OH
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
224
-------
TABLE 3. SINGLE-LABORATORY PRECISION AND ACCURACY
Cr(VI)
Sample Type (/jg/L) (a)
Reagent Water
Drinking Water
Groundwater
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.
225
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METHOD 245.1
DETERMINATION OF MERCURY IN WATER
BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY
Edited by Larry B. Lobring and Billy B. Potter
Inorganic Chemistry Branch
Chemistry Research Division
Revision 2.3
April 1991
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
227
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METHOD 245.1
DETERMINATION OF MERCURY IN WATER
BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY
SCOPE AND APPLICATION
1.1 This procedure1 measures total mercury (organic + inorganic) in
drinking, surface, ground, sea, brackish, industrial and domestic
wastewater.
1.2 The range of the method is 0.2 to 10 p.g Hg/L. The range may be
extended above or below the normal range by increasing or decreasing
sample size or by optimizing instrument sensitivity.
SUMMARY OF METHOD
2.1 A 100-mL portion of a water sample is transferred to a BOD bottle
(or an equivalent flask fitted with a ground glass stopper). It is
digested in diluted potassium permanganate-potasssium 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.
DEFINITIONS
3.1
3.2
3.3
3.4
3.5
3.6
BIOCHEMICAL OXYGEN DEMAND (BOD) BOTTLE - BOD bottle, 300 ± 2 mL with
a ground glass stopper or an equivalent flask, fitted with a ground
glass stopper.
CALIBRATION BLANK - A volume of ASTM type II reagent water prepared
in the same manner (acidified) as the calibration standard.
CALIBRATION STANDARD (CAL) - A solution prepared from the mercury
stock standard solution which is used to calibrate the instrument
response with respect to analyte concentration.
INSTRUMENT DETECTION LIMIT (IDL) - The mercury concentration that
produces a signal equal to three times the standard deviation of the
blank signal.
LABORATORY FORTIFIED BLANK (LFB) - An aliquot of ASTM type II
reagent water to which known quantities of inorganic and/or organic
mercury are added in the laboratory. The LFB is analyzed exactly
like a sample, and its purpose is to determine whether method
performance is within accepted control limits.
LABORATORY FORTIFIED SAMPLE MATRIX (LFM) - An aliquot of a water
sample to which known quantities of a calibration standard are added
228
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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 the
concentrations found.
3.7 LABORATORY REAGENT BLANK (LRB) - An aliquot of ASTM type II reagent
water that is treated exactly as a sample including exposure to all
glassware, equipment, and reagents used in analyses. The LRB is
used to determine if method analyte or other interferences are
present in the laboratory environment, reagents or apparatus.
3.8 LINEAR DYNAMIC RANGE (LDR) - The concentration range over which the
analytical working curve remains linear.
3.9 METHOD DETECTION LIMIT (MDL) - The minimum concentration of mercury
that can be identified, measured and reported with 99% confidence
that the analyte concentration is greater than zero and determined
from analysis of seven LFMs.
3.10 QUALITY CONTROL SAMPLE (QCS) - A water sample containing known
concentration of mercury derived from externally prepared test
materials. The QCS is obtained from a source external to the
laboratory and is used to check laboratory performance.
3.11 WATER SAMPLE - For the purpose of this method, a sample taken
from one of the following sources: drinking, surface, ground,
sea, brackish, industrial or domestic wastewater.
3.12 STOCK STANDARD SOLUTION - A concentrated mercury solution containing
prepared in the laboratory using assayed mercuric chloride or stock
standard solution purchased from a reputable commercial source.
4. 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. 10) must be
strictly followed.
4.2 Volatile materials 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 BOD bottle should be purged
before addition of starinous chloride solution.
5. 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
229
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a potential health hazard and exposure to these compounds should be
minimized by good laboratory practices2. 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 *' 4.
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.
6. APPARATUS AND EQUIPMENT
6.1 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.
6.2 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.
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.
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. Instruments designed
specifically for mercury measurement using the cold vapor technique
are commercially available and may be substituted for the atomic
absorption spectrophotometer.
6.5 BIOCHEMICAL OXYGEN DEMAND (BOD) BOTTLE - See Sect. 3.1.
6.6 DRYING TUBE - Tube (6-in. x 3/4-in. OD) containing 20 g of magnesium
perch!orate. The filled tube is inserted (in-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.
6.3
6.4
230
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6.7 FLOWMETER - Capable of measuring an air flow of 1 L/min.
6 8 MERCURY HOLLOW CATHODE LAMP - Single element hollow cathode lamp or
electrodeless discharge lamp and associated power supply.
6 9 RECORDER - Any multi-range variable speed recorder that is
compatible with the UV detection system is suitable.
6 10 WATER BATH - The water bath should have a covered top and capacity
to sustain a water depth of 2-in. to 3-in. at 95°C ± 1°C. The
dimensions of the water bath should be large enough to accommodate
BOD bottles containing CAL, LFB, LFM, LRB, QCS and water samples
with the lid on.
7. REAGENTS AND CONSUMABLE MATERIALS
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. It is
recommended that the laboratory analyst assay all reagents for
mercury.
7.1.1 Hydroxylamine Hydrochloride (NHpOH'HCl), (CASRN 5470-11-1)
may be used in place of hydroxylamine sulfate (Sect. 7.6);
assayed mercury level of compound is not to exceed 0.05 ppm.
7.1.2 Hydroxylamine Sulfate [(NH2OH)2'H2Sq4], (CASRN 10039-54-0);
assayed mercury level of compound is not to exceed 0.05 ppm.
7.1.3 Mercuric Chloride (HgCl2), (CASRN 7487-94-7).
7.1.4 Nitric Acid (HN03), concentrated (sp.gr. 1.41), (CASRN 7697-
37-2); assayed mercury level is not to exceed 1 ppb.
7.1.5 Potassium Permanganate (KMn04), (CASRN 7722-64-7);
assayed mercury level is not to exceed 0.05 ppm.
7.1.6 Potassium Persulfate (K2S208), (CASRN 7727-21-1); assayed
mercury level is not to exceed 0.05 ppm.
7.1.7 Reagent Water, ASTM type II5.
7.1.8 Sodium Chloride (NaCl), (CASRN 7647-14-5); assayed
mercury level is not to exceed 0.05 ppm.
7.1.9 Stannous Chloride (SnCl2-2H20), (CASRN 10025-69-1);
assayed mercury level is not to exceed 0.05 ppm.
7.1.10 Stannous Sulfate, (SnSO,), (CASRN 7488-55-3); assayed mercury
level is not to exceed 0.05 ppm.
231
,~,
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7.1.11
Sulfunc Acid (H?S04), concentrated (sp.gr. 1.84),
(CASRN 7664-93-9); assayed mercury level is not to
exceed 1 ppb.
7.2
MERCURY CALIBRATION STANDARD - To each volumetric flask used for
serial dilutions, acidify with (0.1 to 0.2% by volume) HNO,
(Sect. 7.1.4). Using mercury stock standard (Sect. 7.3), make
serial dilutions to obtain a concentration of 0.1 0g Hg/mL. This
standard should be prepared just before analyses.
7.3 MERCURY STOCK STANDARD - Dissolve in a 100-mL volumetric flask
0.1354 g HgCl, (Sect. 7.1.3) with 75 ml of reagent water (Sect.
7.1.7). Add 10 ml of cone. HN03 (Sect. 7.1.4) and dilute to mark.
Concentration is 1.0 mg Hg/mL.
7.4 POTASSIUM PERMANGANATE SOLUTION - Dissolve 5 g of KMnO
(Sect. 7.1.5) in 100 mL of reagent water (Sect. 7.1.7);
7.5 POTASSIUM PERSULFATE SOLUTION - Dissolve 5 g of K,S,Oft (Sect. 7 1 6)
in 100 mL of reagent water (Sect. 7.1.7).
7.6 SODIUM CHLORIDE-HYDROXYLAMINE SULFATE SOLUTION - Dissolve 12 q of
N!CJu(nuuV-, 7/c1'8) and 12 g of (NH2OH)2'H2S04 (Sect. 7.1.2) or 12 g
of NH2OH'HC1 (Sect. 7.1.1) reagent water (Sect. 7.1.7) to 100 mL.
7.7 STANNOUS CHLORIDE SOLUTION - Add 25 g of SnCl2'2H20 (Sect. 7.1 9) or
25 g of SnS04 to 250 mL of 0.5 N H2S04 (Sect. ^.8?. This mixture is
a suspension and should be stirrecT continuously during use.
7.8 SULFURIC ACID, 0.5 N - Slowly add 14.0 mL of cone. H?SO,
(Sect. 7.1.11) dilute to 1 L with reagent water (Sect. 7.1.7).
8- SAMPLE COLLECTION. PRESERVATION AND STQRAGF
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
n»Eor,V A11 1tems used in san)Ple preparation should be soaked in 30%
LJMf| /v*-»**^**«1J'\— — -I .-. J _ _ I • i •• .
7.1^7).
> 7i>!\ j r.—r^i »» • u., .JMISU i u i/c ouartcu 111
3 (beet. 7.1.4) and rinsed three times in reagent water (Sect.
8.2
The water sample should be preserved with HN03 (Sect. 7.1.4) to
pH ^ 2.
9. CALIBRATION AND STANDARDIZATION
9.1
Transfer 0.5, 1.0, 2.0, 5.0 and 10 mL aliquots of the 0.1 jug/mL CAL
(Sect. 7.2) to a series of 300-mL BOD bottles. Dilute standards to
232
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100 ml and process as described in Sect. 11.2. These BOD bottles
will contain 0.5 to 1.0 /zg of Hg and are used to calibrate the
instrument.
9.2 Construct a standard curve by plotting peak height or maximum
response of the standards as obtained in Sect. 11.7, versus
micrograms of mercury contained in the bottles. The standard curve
should comply with Sect. 10.2.3. Calibration using computer or
calculator based regression curve fitting techniques on
concentration/response data is acceptable.
10. QUALITY CONTROL
10.1 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 capa-
bility 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.
10.2 INITIAL DEMONSTRATION OF PERFORMANCE.
10.2.1 The initial demonstration of performance is used to
characterize instrument performance (MDLs and linear
calibration ranges) for analyses conducted by this method.
10.2.2 A mercury MDL should be established using reagent water
(blank) fortified at a concentration of two to five times
the estimated detection limit6. 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 is, t = 3.14 for seven replicates.
S = standard deviation of the replicate analyses.
A MDL should be determined every six months or whenever a
significant change in background or instrument response is
expected (e.g., detector change).
10.2.3 Linear calibration ranges - The upper limit of the linear
calibration range should be established for mercury by
233
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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. Linear calibration
ranges should be determined every six months or whenever a
significant change in instrument response is observed.
10.3 ASSESSING LABORATORY PERFORMANCE - REAGENT AND FORTIFIED BLANKS
10.3.1 The laboratory must analyze at least one LRB (Sect. 3.7)
with each set of samples. LRB data are used to assess
contamination from the laboratory environment and to
characterize spectral background from the reagents used in
sample processing. If a mercury value in a LRB exceeds its
determined MDL, then laboratory or reagent contamination is
suspect. Any determined source of contamination should be
eliminated and the samples reanalyzed.
10.3.2 The laboratory must analyze at least one LFB (Sect. 3.5)
with each batch of samples. Calculate accuracy as percent
recovery (Sect. 10.4.2). If recovery of mercury falls
outside control limits (Sect. 10.3.3), the method is judged
out of control. The source of the problem should be
identified and resolved before continuing analyses.
10.3.3 Until sufficient data (usually a minimum of 20 to 30
analyses) become available, each laboratory should assess
its performance against recovery limits of 85-115%. When
sufficient internal performance data become 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
fol1ows:
UPPER CONTROL LIMIT = x + 3S
LOWER CONTROL LIMIT = x - 3S
After each five to ten new recovery measurements, new
control limits should be calculated using only the most
recent 20 to 30 data points.
10.4 ASSESSING ANALYTE RECOVERY - LABORATORY FORTIFIED SAMPLE MATRIX
10.4.1 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. Select a water sample that is
representative of the type of water sample being analyzed
which has a low mercury background. It is recommended that
this sample be analyzed prior to fortification. The
fortification should be 20% to 50% higher than the analyzed
value. Over time, samples from all routine sample sources
should be fortified.
234
-------
10.4.2 Calculate the percent recovery, corrected for background
concentrations measured in the unfortified sample, and
compare these values to the control limits established in
Sect. 10.3.3 for the analyses of LFBs. A recovery
calculation is not required if the concentration of the
analyte added is less than 10% of the sample background
concentration. Percent recovery may be calculated in units
appropriate to the matrix, using the following equation:
_ Q
x 100
10.4.3
11. PROCEDURE
where, R = percent recovery
Cs = fortified sample concentration
C = sample background concentration
s = concentration equivalent of fortifier added to
water sample.
If mercury recovery falls outside the designated range, and
the laboratory performance is shown to be in control
(Sect. 10.3), 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.
11.1 Transfer 100 ml of the water sample [or an aliquot diluted
with reagent water (Sect. 7.1.7) to 100 ml] into a BOD
bottle.
11.2 Add 5 ml of H2S04 (Sect. 7.1.11) and 2.5 ml of HN03
(Sect. 7.1.4) to the sample.
11.3 To each bottle add 50 ml reagent water (Sect. 7.1.7) and 15 ml KMnOA
solution (Sect. 7.4). For sewage or industry wastewaters,
additional KMn04 may be required. Shake and add additional portions
of KMn04 solution, if necessary, until the purple color persist for
at least 15 min. Add 8 ml of KpS208 solution (Sect. 7.5) to each
bottle. Mix thoroughly, cap and cover the top of the BOD bottle
with aluminum foil or other appropriate cover. Heat for 2 h in a
water bath at 95°C.
11.4 Turn on the spectrophotometer and circulating pump. Adjust the pump
rate to 1 L/min. Allow the spectrophotometer and pump to stabilize.
11.5 Cool the BOD bottles to room temperature and dilute in the following
manner:
235
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11.5.1 To each BOD bottle containing the instrument calibration LFB
and LRB, add 50 ml of reagent water (Sect. 7.1.7).
11.5.2 To each BOD bottle containing a water sample, QCS or LFM,
add 55 ml of reagent water (Sect. 7.1.7).
11.6 To each BOD bottle, add 6 ml of NaCl-(NH2OH)2'H2S04 solution
(Sect. 7.6) to reduce the excess permanganate.
11.7 Treating each bottle individually:
11.7.1 Placing the aspirator inside the BOD bottle and
above the liquid, purge the head space (20 to 30
sec) to remove possible gaseous interference.
11.7.2 Add 5 ml of SnCl2 solution (Sect. 7.7) and
immediately attach the bottle to the aeration
apparatus.
11.7.3 The absorbance, as exhibited either on the
spectrophotometer or the recorder, will increase
and reach maximum within 30 sec. As soon as the
recorder pen levels off, approximately 1 min, open
the bypass value (or optionally remove aspirator
from the BOD bottle if it is vented under the
hood) and continue aeration until the absorbance
returns to its minimum value.
11.8 Close the by-pass value, remove the aspirator from the BOD
bottle and continue aeration. Repeat (Sect. 11.7) until
all BOD bottles have been aerated and recorded.
12. CALCULATIONS
12.1 Measure the peak height of the unknown from the chart and read the
mercury value from the standard curve.
12.2 Calculate the mercury concentration in the sample by the formula:
Ha/L =
0911,
n
aliquot
1,000 \
of aliquot)
12.3 Report mercury concentrations as follows: Below 0.2 /zg/L,
< 0.2 /jg/L; between 1 and 10 /w}/L, one decimal; above 10 #g/L, whole
numbers.
13. PRECISION AND ACCURACY
13.1 In a single laboratory (EMSL), using a Ohio River composite sample
with a background mercury concentration of 0.35 Hg /jg/L and
236
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fortified with concentration of 1.0, 3.0, and 4.0 Hg /jg/L, the
standard deviations were ± 0.14, ± 0.10 and ± 0.08 Hg fig/I,
respectively. Standard deviation at the 0.35 Hg /ig/L level was ±
0.16 Hg /jg/L. 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. REFERENCES
1. Kopp, J.F., Longbottom, M.C., and Lobring, L.B., " 'Cold Vapor1
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.
237
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TABLE 1. INTERLABORATORY PRECISION AND ACCURACY DATA
FOR FLAHELESS ATONIC ABSORPTION
Number True Values
of Labs UQ/L
Mean Value
fla/L
Standard
Deviation
RSD Mean
% Accuracy as
% Bias
76
80
82
77
82
79
79
78
0.21
0.27
0.51
0.60
3.4
4.1
8.8
9.6
0.349
0.414
0.674
0.709
.41
.81
8.77
9.10
3.
3.
0.276
0.279
0.541
0.390
49
12
69
3.57
89
67
80
55
44
29
42
39
66
53
32
18
0.34
-7.1
-0.4
-5.2
238
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O * BUBBLER
ABSORPTION
CELL
SAMPLE SOLUTION
IN BOO BOTTLE
SCRUBBER
0-4*"* CONTAINING
A MERCURY
ABSORBNO
MEDIA
Flgurt 1. Apparatus for FlaaeUss Itercury Iteterainatlon
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 a exhaust hood or pass the vapor through some absorbing media, such
as: a) equal volumes of 0.1 N KMnO, and 10% H2S04
b) 0.25% iodine in a 3X KI 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.
239
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METHOD 245.3
DETERMINATION OF INORGANIC MERCURY (II) AND SELECTED OR6ANOMERCURIALS IN
DRINKING AND GROUND WATER BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY
(HPLC) WITH ELECTROCHEMICAL DETECTION (ECD)
Otis Evans and Betty Jacobs
Inorganic Chemistry Branch
Chemistry Research Division
Revision 1.1
April 1991
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
241
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METHOD 245.3
DETERMINATION OF INORGANIC MERCURY (II AND SELECTED ORGANOMERCURIAL S IN
HELS
SCOPE AND APPLICATION
lpl ™™,meth°d -S aPP]ic?b?? to the determination of certain dissolved
mercury species in drinking and ground water.
1.2 The analytical range is approximately 2 /*g/L to 10 mg/L inorganic
mercury (II) and organometallic mercury compounds.
1.3
The method detection limits (MDLs) are 1.8 ng/i for mercury (II)
1.9 /*g/L for methyl mercury, 1.7 jug/L for ethylmercury, and 0.8 '
for phenyl mercury.
1.4 This method should be used by analysts experienced in liquid
chromatography with electrochemical detection (LCEC).
2. SUMMARY OF METHOD
2.1
This method describes a procedure for the speciation of certain
dissolved mercury ionic analytes in drinking and ground water
Inorganic mercury (II), methyl mercury, ethylmercury, and
phenylmercury are determined by reversed-phase HPLC with reductive
amperometric electrochemical detection1'6. The mercury analytes are
neural I°HP° *" ?lth ^captoethanol (2-ME) to form charge
SI* i ?? *: T?e mercury complexes are eluted with 60% (w/w)
methanol (isocratic elution conditions) buffered at pH 5 5 The
1ll at a f1ow rat^ °f 0.6
3. DEFINITIONS
3>1
3.2
hp«rf a!Id F52) - Two separate sat"Ples collected at
the same time and placed under identical circumstances and treated
of FD yan5%nr-thr°U9h field andulab°^tory procedures. Analyses
of FD1 and FD2 give a measure of the precision associated with
sample collection, preservation and storage, as well as with
laboratory procedures.
FIELD REAGENT BLANK (FRB) - Reagent water placed in a sample
container in the laboratory and treated as a sample in all respects
including exposure to sampling site conditions, storage respects'
preservation and all analytical procedures. The -purpose of the FRB
r^Pnde-eThnVfifth°? analytes or other interferences are
present in the field environment.
242
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3 3 LABORATORY DUPLICATES (LD1 and LD2) - Two sample aliquots taken in
the analytical laboratory and analyzed separately with identical
procedures. Analyses of LD1 and LD2 give a measure of the precision
associated with laboratory procedures, but not with sample
collection preservation, or storage procedures.
3.4 LABORATORY FORTIFIED BLANK (LFB) - An aliquot of reagent water 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 at the required detection limit.
3 5 LABORATORY PERFORMANCE CHECK SOLUTION (LPCS) - A solution of method
analytes used to evaluate the performance of the LCEC system with
respect to a defined set of method criteria.
3.6 LABORATORY REAGENT BLANK (LRB) - An aliquot of reagent water that is
treated exactly as a sample. It is exposed to all the glassware,
method solvents, and reagents that are used with other samples. The
purpose of the LRB is to determine if method analytes or other
interferences are present in the laboratory environment, the
reagents, or the apparatus.
3 7 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.
3.8 ORGANOMETALLIC COMPOUNDS - Compounds in which the carbon atoms of
organic groups are bound to metal atoms.
' 39 PRIMARY DILUTION STANDARD SOLUTION - A solution of several analytes
prepared in the laboratory from stock standard solutions and diluted
as needed to prepare calibration solutions and fortified blanks.
3.10 SPECIATION - The determination of certain individual physico-
chemical forms of an element.
3.11 STOCK STANDARD SOLUTION - A concentrated solution containing a
single certified standard that is a method analyte, or a
concentrated solution of a single analyte prepared in the laboratory
with an assayed reference compound. Stock standard solutions are
used to prepare primary dilution standards.
3.12 QUALITY CONTROL SAMPLE (QCS) - A sample matrix containing method
analytes or a solution of method analytes in a water miscible
solvent which is used to fortify reagent water or environmental
samples. The QCS is obtained from a source external to the
laboratory, and is used to check laboratory performance with
externally prepared test materials.
243
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i 1
dil
n! SOlUti°n prePared from the
standard solution and stock standard solutions. The CAL
the
3.14 AMPEROMETRIC DETECTOR - An electrochemical detector employing a
rp£Sg elefr?deji whi'h is kePt at a constant potential verLs a
reference electrode. A small portion of the electroactive species
JifrJI9! ? electrode is electrolyzed (reduced or oxidized) and the
electrolysis current is a function of the concentration of the
eluted electroactive material.
ELECTRODE (GAME> - A
gold
4. INTERFERENCES
4.1
4.2
4.3
4'4
cnivl ferences m this method may be caused by contaminants in
solvents, reagents, glassware, Teflon bottles (metals storage), and
JrJlftS? Pr°ef^H aP?aratus- These interferences may lead to
artifacts or elevated baselines in liquid chromatograms All
reagents and apparatus must be routinely demonstrated to be free
°f the
4.1.1 Glassware and Teflon bottles must be scrupulously cleaned
Soak in concentrated nitric acid and -rinse thoroughly with
organic free deionized, distilled water. If these
containers are used for free metal and organometal solution
preparation and storage they should be soaked and filled
SS J 5 ^i1? ()[/Vl Solut1on of m'tric acid for one week,
rinsed, sealed and stored containing deionized, distilled
water.
4.1.2 The use of high purity reagents and solvents helps to
minimize interference problems. Purification of solvents by
distillation in all-glass systems may be required.
Interfering contamination may occur when a sample containing low
concentrations of analytes is analyzed immediately following a
sample containing relatively high concentrations of analytes A
preventive technique is between-sample rinsing of the sample 'syrinqe
and sample loop with methanol and/or water. After analysis of I
sample containing high concentrations of analytes, one or more
laboratory reagent blanks should be analyzed.
tho eamni -TU" may ?e "used by contaminants that are present
... the sample. The extent of matrix interference will vary
considerably from source to source, depending upon the sample type.
Electrochemical interferences are caused by species which are
electrochemically active (i.e., reducible at the surface of the
244
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GAME) and have retention times which are the same or very similar to
the analytes (or because of the type of reduction process can
produce broad chromatographic responses which obscure large portions
of the resultant chromatograms).
Amperometric (reductive) electrochemical detection of mercury
analytes requires the complete removal of oxygen from the eluent and
sample (1,2,10,11,13-15). (Solutions in atmospheric equilibrium
typically contain 10~4 to 10~3 M oxygen. The specific reaction(s)
depends on electrode material, potential, and electrolyte
composition). The presence of oxygen results in two distinct yet
closely related problems: mobile phase oxygen and sample oxygen.
Mobile phase oxygen contributes to onerous residual currents that
make trace measurements virtually impossible. To lower mobile phase
oxygen to acceptable levels, deoxygenation can be facilitated by a
combination of sparging with inert gas (insufficient alone) and
warming of the eluent solution.
4.4.1 Sample oxygen is retained on reversed-phase columns (not
eluted in the void volume) and elutes as a broad, tailing
band. Its retention time is independent of the
concentrations of the mobile phase constituents; therefore,
manipulation of the elution position is difficult. Oxygen
is detected as a peak when only the mobile phase is purged
(sparged) with inert gas. Elimination of the sample oxygen
interference can be accomplished by purging with an inert
gas prior to injection. The sample is placed in a 3 to 5 ml
vial, as shown in Figure 2b, and purged with a stream of
inert gas for « 5 min. The sample aliquot is introduced
into the sample injection loop via a closed system to
prevent reentry of oxygen .
4.4.2 Mobile phase oxygen. Both positive and negative oxygen
peaks can arise in LCEC. The former occurs when the sample
solution is not purged with an inert gas. A negative oxygen
peak occurs when the mobile phase contains more oxygen than
the sample. The negative peak has the same retention time
and shape but may be lower in magnitude then the positive
oxygen peak.
5. SAFETY
5.1 The toxicity or carcinogenicity of each reagent used in this method
has not been precisely defined; however, each chemical compound must
be treated as a potential health hazard. The 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 safety data sheets
should also be made available to all personnel involved in the
chemical analysis. Additional references to laboratory safety
should be identified and made available for the information of the
personnel using this method.
245
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The current OSHA standard for organo (alkyl) mercury is 0.01 mg of
organo (alkyl) mercury per cubic meter of air (mg/m*) averaged over
an eight-hour work shift with a ceiling level of 0.04 mg/m?. Organo
(alkyl) mercury can affect the body if it is inhaled, cSmes 1nUrgan°
contact with the eyes or skin, or is swallowed. It may enter the
body through the skin. Skin that becomes contaminated with organo
(alkyl) mercury should be immediately washed or showered with soao
or mild detergent and water.
If organo (alkyl) mercury compounds are spilled or leaked:
1. Remove ignition sources.
2. Ventilate area of spill or leak.
3. If in the solid form, collect for reclamation or
disposal.
5.1.1
5.1.2
5.1.3
5.1.4
6.
4. If in the liquid form, absorb on paper towels.
Evaporate in a safe place (such as a fume hood).
The addition of the complexing agent, 2-Mercaptoethanol (2-
ME), should be performed in a hood.
The eluent pH should be adjusted in a hood.
Precautions must be taken in the preparation of the GAME to
prevent aerosols and spills.
Disposal of waste (solvents, analytes, etc.) from the
system must be according to local regulations.
APPARATUS AND EQUIPMENT (Some specifications are suggested)
6.1 HIGH PERFORMANCE LIQUID CHROMATOGRAPH
6.1.1 An HPLC system designed for pumping solvents at precisely
controlled flow rates and pressures. The system should be
capable of injecting 10- to 200- juL aliquots.
NOTE: Amperometric reductive electrochemical detection of
the mercury analytes requires the complete removal of oxygen
from the eluent and samples. Copper tubing (1/8 in.) may be
used for lines from the purge gas (Ar) tank to the mobile
phase flask. Fittings and tubing (1/16 in. o.d )
. .
constructed ^om type 316 stainless steel should be used for
all other connections '10f11'14'15.
6.1.2 Analytical column— 25 cm x 4.6 mm I.D. stainless steel
packed with LiChrosorb RP-18 (5 urn irregularly shaped
246
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particles) hydrocarbon phase (C-18 (ODS)) bonded silica (EM
Science) or equivalent.
613 Guard column—70 mm x 4.6 mm I.D. stainless steel packed
with Perisorb RP-18 (30-40 urn) (EM Science) or equivalent.
6.1.4 Pre-column (saturator column)—70 mm x 4.6 mm I.D. stainless
steel packed with spherical silica (18 urn) (EM Science) or
equivalent.
6.1.5 Electrochemical detector (potentiostat/current amplifier).
6.1.5.1 Working electrode. - GAME.
6.1.5.2 Reference electrode - Ag/AgCl 3M NaCl).
6.1.6 Other columns or detectors may be used if the requirements
of Sect. 10.5 can be met.
6.2 Strip Chart Recorder - Variable speed.
6.3 Balance—Analytical, capable of accurately weighing to the nearest
0.01 mg.
6.4 General purpose laboratory, top-loading, metric, automatric
calibration, full range-taring readibility to 0.01 g.
6.5 Filtration Apparatus—To filter samples and mobile phases used in
HPLC, use 250 ml glass reservoir (connects to 1 L bottle or vacuum
flask), funnel base and stopper, clamp, stainless steel holder,
screen and Teflon gaskets (Figure 3). Recommended are 47-mm filters
(Millipore Type HA, 0.45 /xm, for water and Millipore Type FH, 0.5-
nm, for organics or equivalent).
6.6 GLASSWARE
6.6.1 Three-neck distillation flask with all equivalent height
necks of I 24/40 joints.
6.6.2 Condenser, Graham, Drip Tip Inner (bottom) and Outer (top) I
24/40 Joints. .
6.6.3 Reaction vials—5-mL capacity serve as sample cells and
purge gas saturation chambers.
6.6.4 Bubbler—I 29/42 joints (frit not required).
6.6.5 Connecting Adapter, I 24/40 joint (condenser end).
6.7 Standard 1-L heating mantle.
247
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6'8
°f maintain1n9 temperatures within
6.9 Thermistor probe— Heavy duty laboratory style (~20 cm long).
6.10 Septa— White rubber for I 24/40 joints.
6.11 Refrigerated Recirculating Cooler— With sealable reservoir
temperature controller, recirculating pump, air cooled refrigeration
(± l.OC). Circulation is in a closed loop configuration (system).
6.12 SYRINGES
6.12.1 Hypodermic syringe— 5 mL glass (gas tight).
6.12.2 Microliter gas tight syringe— 50 /*L an 100 ;uL needle: 90°
blunt tip, 2" long, 0.028" OD (22S gauge), no electrotaper.
7- REAGENTS AND CONSUMABLE MATERIALS
7.1 Acetonitrile (CASRN-75-05-8)— HPLC grade.
7.2 Deionized, distilled water (CASRN-7732-18-5): Prepared by passing
distilled water through mixed bed cation and anion exchange resin?.
^?i^??nZed; dHStilled/^?r for a11 ^agents, eluent solutions,
calibration standards and dilutions. In this method, the term
deionized distilled water will be used interchangeably with reagent
mShL(H'?"^ater-1-/hIch,an interferent is not observed at the
method detection limit of the compounds of interest).
7.3 Inert Gas— High purity argon or helium for degassing eluents and
samp i es .
7.4 HPLC MOBILE PHASE
7.4.1 Acetic acid, Glacial (CASRN-64-19-7)— Ultrex grade (for
eluent pH adjustment). y v
7.4.2 Ammonium hydroxide (CASRN-1336-21-6)-Ultrex grade, 20% (for
eluent pH adjustment).
7.4.3 Eluent: Mix 600 g of methanol (Sect. 7.4.5) and 400 g water
(Sect. 7.2.), pH 5.5, add 200 juL of 2-mercaptoethanol to 1-
L of solution. (The total volume is « 1.125 L.) Allow to
cool, adjust the pH, transfer to a 1-L volumetric flask
(refrigerate the remainder) and add the complexing agent
(Sect. 7.4.4)).
7.4.4 2-Mercaptoethanol (CASRN-60-24-2)-CAUTION: Combustible
stench, harmful vapor; store in hood.
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7.4.5 Methanol (CASRN-67-56-l)--High purity solvent, HPLC grade.
7.5 Ethylmercury chloride (CASRN-107-27-7).
7.6 Mercuric chloride (CASRN-7487-94-7).
7.7 Mercury, metal (CASRN-7439-97-6)—Triple distilled.
7.8 Methylmercury chloride (CASRN-115-09-3).
7.9 Nitric acid, cone. (CASRN-7697-37-2)--sp gr 1.41.
7.10 Nitric acid, 1:1: Add 50 ml cone. HNO, (Sect. 7.9) to 40 ml of
distilled, deionized water (Sect. 7.2), cool, and dilute to 100 ml.
7.11 Phenylmercury acetate (CASRN-62-38-4).
7.12 Sodium chloride (CASRN-7647-14-5)—CrystalI, ACS grade, 3M. Dissolve
43.8 g of sodium chloride in deionized, distilled water (Sect. 7.2)
and dilute to 250 ml.
7.13 Stock standard solutions (1000 ng/ml) of the mercury analytes may
be prepared from reagent grade chemicals. Typical metal stock
solution preparation procedures follow. The amount of organic
solvent, acetonitrile, (Sect. 7.1) is added as needed in order to
dissolve the particular mercury organometal.
7.13.1 Mercury (II) solution, stock, 1 mg/mL: Dissolve 0.1354 g of
mercuric chloride (Sect. 7.6) in deionized, distilled water
with stirring until completely dissolved. Transfer to a
100 ml volumetric flask and dilute to volume. Transfer to a
125-mL Teflon bottle and refrigerate. This solution can be
stored and used for at least six months.
7.13.2 Methylmercury solution, stock, 1 mg/mL methylmercury:
Dissolve 0.5822 g of methyl mercuric chloride (Sect. 7.8) in
deionized, distilled water (minimum volume of water added
initially) with constant stirring. Add acetonitrile (Sect.
7.1) slowly until dissolution is complete. In 500 ml total
volume, approximately 10% (V/V) CH3CN is sufficient to
dissolve this amount of material. Dilute to 500 ml total
volume and transfer to a Teflon bottle for refrigeration and
storage. This solution can be stored and used for at least
six months.
7.13.3 Ethylmercury solution, stock, 1 mg/mL ethylmercury:
Dissolve 0.5771 g of ethylmercuric chloride (Sect. 7.5) in
deionized distilled water with constant stirring. Because
Ethylmercuric chloride is difficult to dissolve in water,
add acetonitrile (Sect. 7.1) until there is complete
dissolution. Approximately 200 ml of 40% (V/V) acetonitrile
249
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7.13.4
NOTE:
(Sect. 7.1), is needed. Dilute to 500 mL with distilled,
deionized water (Sect. 7.2), transfer to a Teflon bottle for
refrigeration and storage. This solution can be stored and
used for at least six months.
Phenylmercury solution, stock, 1 mg/rnL phenylmercury:
Dissolve 0.6063 g of phenylmercuric acetate (Sect. 7 in
Add approximately 10% (V/V) acetonitrile (Sect. 7.1) to aid
in dissolution. Dilute to 500 ml with deionized, distilled
water (Sect. 7.2) and refrigerate in a Teflon bottle. This
solution can be stored and used for at least six months.
For analysts who do not routinely perform mercury analyses
or do not wish to generate excessive amounts of mercury
waste, the stated volumes and/or amounts of organometal
salts should be reduced proportionately. Primary and
secondary dilution standards may be diluted to 10 mL or 25
ml of solution to avoid this problem.
8- SAMPLE COLLECTION. PRESERVATION AND HAMni TMfi
8'2
rn n lectlon:-?aniples should be collected in duplicate in amber
colored glass containers or glass containers wrapped in aluminum
collection containers should not be Prerinsed with sample prior to
8.1.1
8.1.2
When sampling from a water tap, open the tap and allow the
system to flush until the water temperature has stabilized
Adjust the flow to about 500 mL/min and collect duplicate
samples from the flowing stream. MH'".*HJ
When sampling from an open body of water, fill the sample
container with water from a representative area. Sampling
equipment, including automatic samplers, must be free of
plastic tubing and other components that may leach
interferents into the water. Automatic samplers that
composite samplers over time must use refrigerated
glass/Teflon sample containers.
be iced or refrigerated at
until filtration. The samples
poss1ble
-------
8.4 FIELD BLANKS
8.4.1 Processing a field reagent blank (FRB) is recommended along
with each sample set, which is composed of the samples
collected from the same general sample site at approximately
the same time. At the laboratory, fill a sample container
with reagent water, seal, and ship to the sampling site
along with the empty sample containers. Return the FRB to
the laboratory with filled sample bottles.
NOTE: The prevention of contamination and losses is of paramount
importance in organomercury speciation and analysis.
Potential sources of contamination in the laboratory
environment are dust, reagent impurities, and sample contact
with laboratory apparatus (resulting in contamination by
leaching or surface desorption). Depletion of mercury via
adsorption onto container surfaces must also be considered.
9. CALIBRATION AND STANDARDIZATION
9.1 Establish LCEC operating conditions equivalent to those indicated in
Table 1. Calibrate the HPLC system using the external standard
technique.
9.2 EXTERNAL STANDARD CALIBRATION PROCEDURE
9.2.1 An external standard is a solution containing a known amount
of a pure compound that is analyzed with the same procedures
and conditions that are used to analyze samples containing
that compound. From measured detector responses to known
amounts of the external standard, a sample concentration of
that compound can be calculated from measured detector
response to that compound in a sample analyzed with the same
procedures.
9.2.2 At least three calibration standards are needed. One should
contain each analyte at a concentration near to but greater
than its method detection limit (MDL) (Table 2); the other
two should bracket the concentration range expected in the
samples or define the working range of the detector. For
example, if the MDL is 1.0 M9/L and a sample is expected to
contain approximately 5.0 Atg/L, aqueous standards should be
prepared at concentrations of 2.0 p.g/1, 5.0 p.g/1, and
10.0
9.2.3 Inject 0.1 mL of each calibration standard and tabulate peak
height or area response versus the concentration of the
standard. The results are to be used to prepare a
calibration curve for each analyte by plotting the peak
height or area versus the concentration.
251
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9.2.4 The working calibration curve must be verified on each
working day by the measurement of one or more calibration
standards (and when/if the working electrode is changed
between analyses). If the response for an analyte varies
from the response predicted by the calibration curve (Sect.
9.2.2) by more than ± 10%, the test must be repeated using
a fresh calibration standard. If the results still do not
agree (i.e., the response is off by more than
± 10%), generate a new calibration curve for each analyte.
(Assuming that the electrode surface is "fatigued", the
analyst should change the GAME before proceeding further)
Generally the electrode can be used 3 to 4 days before the
old amalgam surface has to be removed.
9.2.5 Single point calibration is sometimes an acceptable
alternative to a calibration curve. Single point standards
should be prepared from the primary dilution standard
solutions. The single point calibration standard(s) should
be prepared at a concentration that produces a response
close (± 10%) to that of the unknowns.
10. QUALITY CONTROL
10.1 Each laboratory using this method is required to operate a quality
control (QC) program. The minimum requirements of this program
consist of the following: an initial demonstration of laboratory
capability and regular analyses of laboratory reagent blanks
(including sol vent/eluent blanks) and laboratory fortified blanks
(laboratory QC samples). The laboratory must maintain records to
document the quality of the data generated.
10.2 Initial demonstration of low system (detector) background response
(i.e., minimum residual (background) current and low noise output).
10.2.1 The system must operate with the minimum absolute background
current in order to optimize sensitivity. Detection of
analytes at low concentrations (e.g., 20 /zg/L) can result
in chromatograms being superimposed on a background current
which may exceed the peak heights of the analytes. High
background currents may increase instrumental susceptibility
to flow variation noise and possibly lead to nonlinear
deviations in the calibration curve(s). The Faradaic
response, which may arise from an electrochemical reaction
of the electroactive impurities in the mobile phase (eluent)
is the principal component of the current produced at a
constant potential detector. The most common sources of
background current are the oxidation/reduction of the eluent
or buffer salts, oxygen (either eluent or sample), ferrous
and/or ferric iron and other metals ions.
252
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10.2.2 The noise associated with an electrochemical detector is
dependent on the magnitude of the background signal. In
general, the higher the background, the higher the noise.
The ratio of the noise to the background current stays about
the same. Noise can be random or periodic and superimposed
on the steady state background signal. The noise represents
the collective contributions from pump pulsations, flow cell
hydrodynamics, surface reactions, static electricity, power
line noise, and electronic signal amplification. Noise can
be minimized by (a) obtaining pulseless flow, (b) frequent
system passivation, (c) proper maintenance of pump seals and
check values in order to minimize flow fluctuations, (d)
proper system grounding, and (e) careful scrutiny of the
working electrode surface—a smooth, shiny mirror-like
finish is desirable.
10.3 Another possible source of noise is the reference electrode which
provides a stable, reproducible voltage to which the working
electrode potential maybe referenced. The potential value should
not vary with time and should be reproducible from electrode to
electrode. Leaks can occur due to drying and cracking of the porous
plug. As a consequence, the internal electrolyte concentration
changes and subsequently the reference potential.
10.4 Air bubbles trapped around and/or between the working and reference
electrode can cause noise, random as well as periodic with constant
amplitude and frequency.
10.5 Initial demonstration of laboratory accuracy and precision. Analyze
seven replicates of a laboratory fortified blank solution
(laboratory QC samples) containing each analyte at concentration
levels near the low calibration standard. (See regulations and
maximum contaminant levels for guidance on appropriate
concentrations.)
10.5.1 Prepare each replicate by adding an appropriate aliquot of
the primary/secondary dilution standard solution, or other
certified quality control sample, to reagent water. Analyze
each replicate according to the procedure described in
Sect. 11.
10.5.2 Calculate the measured concentration of each analyte in each
replicate and the mean accuracy (as mean percentage of true
value) and precision (as relative standard deviation, RSD)
of the seven measurements of each analyte.
10.5.3 For each analyte at 50 M9/U the mean accuracy expressed as
a percentage of the true value is approximately 93% and the
RSD is < 11%.
253
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10.5.4 Analysts should develop and maintain a system of control
charts to plot the precision and accuracy of analyte
measurements over time.
10.5.5 It is recommended that the laboratory periodically document
and determine its detection limit capabilities for the
analytes of interest. NOTE: The determination of the
method detection limit (MDL) for this method was performed
under special (ideal) experimental conditions in order to
achieve the desired level. The GAME was specially prepared
and the system was allowed to equilibrate over a 4 day
period. Eluent flow was maintained at approximately 0.3-
0.4 mL/min. The current sensitivity was increased until the
lowest setting was achievable. The MDL of each analyte was
calculated (Table 2) using procedures described in12. The
listed MDLs should be achievable or lower with commercially
available instrumentation, which include improved solvent
delivery systems, new transducer cell designs, and
installable in-line deoxygenators that remove at least 99%
of the oxygen in the sample and mobile phase without
affecting their integrity. Analyte detection at regulatory
levels should be achievable.
10.6 Laboratory Reagent Blanks (LRB) Before processing any samples, the
analyst must demonstrate that all glassware and reagent
interferences are under control. Each time a set of reagents is
changed (fresh eluent added) or a new working or reference electrode
installed, a LRB must be analyzed. If within the retention time
window of any analyte of interest the LRB produces a peak that would
prevent the determination of that analyte, determine the source of
contamination and eliminate the interference before processing
samples.
10.7 A single laboratory fortified blank containing each mercury analyte
at a concentration as specified in Sect. 10.5 must be analyzed with
each set of samples. Evaluate the accuracy of the measurements.
Any problems must be located and corrected before further analyses
are performed.
10.8 A field reagent blank should be analyzed with each set of field
samples. Data/information from these analyses will be used to help
define and determine contamination related to field sampling and
transportation activities.
10.9 Each quarter, replicate laboratory fortified blanks must be analyzed
to determine the precision of the laboratory measurements. These
data will be used in documenting data quality.
10.10 Each quarter, the laboratory must analyze a quality control sample
obtained from an external source. A quality control sample should
be analyzed each time a new set of standards are used. The entire
254
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analytical procedure must be checked, if unacceptable accuracy data
is obtained.
10.11 The laboratory must analyze an unknown performance evaluation
sample (if available) at least once per year. Results for each
analyte must be within established acceptance limits.
11. PROCEDURE-LIQUID CHROHATOGRAPHY WITH ELECTROCHEMICAL DETECTION (LCEC)
11.1 Table 1 summarizes the recommended operating conditions for LCEC
and presents analyte retention times observed using this method.
The operating conditions may be changed (e.g., flow rate, modifier
percent, electrode potential, etc.) in order to enhance the
separation or detection.
11.2 CHROMATOGRAPHIC PROCEDURES
11.2.1 Electrode (cell) preparation: The cell should be polished
before use . From beginning use, and regularly during
its use, a new mercury film must be deposited on the gold
disk. Follow the procedure for electrode preparation as
stated in the operator's manual.
Mercury application—This process should be carried out in
a tray in the event of an accidental spill. Follow the
precautions for handling mercury. NOTE: Mercury has a
high vapor pressure and should always be stored in a
closed container or under water. Prior to mercury
application rinse the electrode surface with a small
amount of methanol and air-dry before proceeding.
Deposition of the mercury film on the gold disk
is accomplished by placing a small drop of mercury on the
gold surface. Cover the entire surface with mercury using
a disposable pi pet. Wait ~ 3-5 minutes, then remove the
excess mercury gently with the sharp edge of an index
card. (This step may be repeated 2 to 4 times). The
mercury surface can be smoothed with a soft tissue (lens
tissue works best) to obtain a shiny, mirror finish.
(DISPOSE OF WASTE MERCURY CAREFULLY.) If excess mercury
is left on the electrode, there is a possibility of a
short circuit with the auxiliary electrode (stainless
steel top). In some instances, the insertion of a second
gasket between the electrode cube halves can remedy the
problem. Sometimes it is not necessary to remove the old
amalgam surface before a fresh mercury surface can be
applied. The new mercury surface can be formed on top of
the old amalgam. Follow the same procedure as for a fresh
gold surface.
255
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The amalgam requires a period of equilibration following
its formation. Usually allowing the amalgam to rest
overnight is sufficient.
11.3 SYSTEM OPERATION
11.3.1
11.3.2
11.3.3
11.3.4
12. CALCULATIONS
The instrumentation should be turned on and allowed to
become stable before beginning.
The following chromatographic start-up procedure is
recommended for reductive LCEC analysis f2.
DEOXYGENATION: Before initiating flow through the LC
system, the eluent, which is placed in a 2-L distillation
flask, is refluxed at 40 ± 5°C while being purged
vigorously with inert gas (argon or helium) for
approximately 1-2 hours (Figure 2A). Then the degassed
mobile phase is pumped through the LCEC system to force
out any oxygen entrained in the stationary phase pores
(column interstices). Degassing the system may require
100-150 mL of mobile phase. The system must be flushed
thoroughly. Next, the working electrode is turned on
(after flushing) using the least sensitive gain setting.
The current is monitored until the background current has
stabilized in the desired range, usually 80 to 100 nA.
Sample degassing is necessitated when working at
potentials more negative than -0.1 V for the GAME10'14'15.
Care must be taken in order to preserve the sample's
original composition. The purge gas should be
presaturated with mobile phase or water and flowed gently
through the sample to minimize its evaporation. Degassing
a 3.5-4 mL sample requires approximately 5 min.
Sample injection requires a closed system. The
injection valve inlet is immersed in the filtered and
degassed sample solution and the sample aliquot is slowly
drawn into the injection loop by gentle suction
(Figure 2C)1'11'1"'Ti. Exposure to oxygen is avoided and
the integrity of the closed system is preserved.
12.1
12.2
Calculate analyte concentrations in the sample by utilizing the
calibration curve(s) generated from the responses of analytes in
standard solutions.
Data should be rounded to the tenths place and reported in
micrograms per liter.
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13. PRECISION AND ACCURACY
13.1 In a single laboratory the MDL12 was determined for each analyte.
Seven aliquots of the fortified distilled water sample were
measured and the results used to calculate the MDL at the 99%
confidence level. The calculated MDLs (Table 2) ranged from 0.8 to
1.9 M9/L.
13.2 In a single laboratory, analyte recoveries from laboratory
distilled water, tap water, and two groundwaters were determined at
analyte concentrations ranging from 50 to 200 /zg/L (Tables 3-5).
Recoveries averaged 90 ± 7% RSD with comparable values obtained
over the entire range of concentrations. The standard deviation of
the measurements on all waters was approximately 1.52 jug/L with an
RSD of approximately 0.64%.
14. REFERENCES
1. Evans, 0. and McKee, 6.D., Analyst. 1987, 112, 983.
2. Evans, 0. and McKee, G.D., Analyst. 1988, 113, 243.
3. MacCrehan, W.A., Durst, R.A., and Bellama, J.M., Anal. Lett.. 1977,
10, 1175.
4. MacCrehan, W.A., Durst, R.A., and Bellama, J.M., Nat. Bur. Stand.
(U.S.), Spec. Pub!., 1977, No.519, 57.
5. MacCrehan, W.A. and Durst, R.A., Anal. Chem.. 1978, 50, 2108.
6. MacCrehan, W.A., Anal. Chem.. 1981, 53, 74.
7. Holak, W., >L. Liq. Chromatoqr.. 1985, 8, 563.
8. Holak, W., Analyst. 1982, 107, 1457.
9. Krull, I.S., Bushee, D.S., Schleicher, R.G., and Smith, S.B., Jr.,
Analyst. 1986, 111, 345.
10. "Installation/Operations Manual for Amperometric Controller and
Transducer Package," Bioanalytical Systems, West Lafayette, IN,
1984.
11. Jacobs, W. Curr. Sep. 1982, 4, 45.
12. Glaser, J.A., Foerst, D.L., McKee, G.D., Quave, S.A., and Budde,
W.L., Environ. Sci. Techno!.. 1981, 15, 1426.
13. Lewis, J.Y., Zodda, J.P., Deutsch, E., and Heineman, W.R., Anal.
Chem.. 1983, 55, 708.
257
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14. Bratin, K., and Kissinger, P.T., Talanta. 1982, 29, 365.
15. Bratin, K., and Kissinger, P.T., J. Lia. Chromatoqr.. 1981, 4,
(Suppl.2), 321.
258
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TABLE 1. PRIMARY CHROMATOGRAPHIC CONDITIONS
Absolute Retention Time, Min
Analyte
Mercury (II)
Methyl mercury
Ethyl mercury
Phenyl mercury
(a)
3.3
3.5
4.2
5.3
(b)
5.4
5.9
6.9
9.2
(a) Flow rate - 1.0 mL/min.
(b) Flow rate - 0.6 mL/min.
Primary Conditions:
Analytical Column: 25 cm x 4.6 mm i.d., EM Science LiChrosorb
RP-18 (5/zm)
Pre-Column: Saturator Column, 70 mm x 4.6 mm i .d. (18 /xm) EM
Science
Guard Column: 70 mm X 4.6 mm i.d., EM Science
Peri sorb RP-18 (30-40
Mobile Phase: Isocratic elution - 60% (w/w) methanol ,
0.01% (V/V) 2-mercaptoethanol , pH 5.5 acetate
buffered
Flow Rate: 1.0 mL/min or 0.6 mL/min*
Injection volume: 100 juL
Detector: Electrochemical (GAME); - 0.800 V vs. Ag/AgCl
*The optimum flow rate is « i.o mL/min. However, in some instances it is
desirable to use a lower flow rate. A flow rate of 0.6 mL/min allows a
slightly better separation between Hg(II) and CH,Hg+ than a flow rate of 1.0
mL/min. The lower flow rate does, however, result in approximately a 6-12%
decrease in the analytical signals.
259
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TABLE 2. METHOD DETECTION LIMIT (MDL) (a)
Parameter
Retention time, min
MDL*, /tg/L
Hg(II)
=5.3
*1.8
CH3Hg+
=5.8
*1.9
C2H5Hg+
=6.9
=1.7
C6H5Hg+
=9.5
=0.8
(a) Experimental conditions: 60% (W/W) CH3OH, pH 5.5 acetate buffer, 200 pi
of 2-mercaptoethanol (ME). Potential, - 0.800V vs. Ag/AgCl; flow rate
0.6 mL min- 1. Other conditions: 100 fj,l sample loop; « 45.5°C, « 2250
Ib in "2; current offset ca. - 20 nA; GAME; and LiChrosorb RP-18 (5 jum)
(25cm x 4.6mm i.d.). *For the MDL determination seven replicate
measurements were made on solutions containing each analyte (12). The
fortified value (true concentration) of each analyte is 10
260
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TABLE 3. RECOVERY OF ANALYTES FROM REAGENT WATER (a)
Mixture
A
B
C
Hg Analytes
HgdD
CH3Hg+
C2H5Hg+
C6H5Hg+
Hg(H)
CH3Hg+
C2H5Hg
C6H5Hg+
Hg(ll)
CH3Hg+
C2H5Hg'f
C6H5Hg+
Hg added
M9 L'1
120
120
120
120
150
150
150
150
250
250
250
250
Hg determined
M9 L"1
(mean ± s.d.)
113.2 ± 2.1
117.1 ± 1.4
118.4 ± 1.5
123.2 ± 0.8
153.0 ± 1.3
154.6 ± 1.4
154.4 ± 1.4
143.3 ± 0.3
249.0 ± 0.8
255.7 ± 1.6
255.2 ± 2.2
250.5 ± 0.8
Recovery, %
(mean ± s.d.)
94.4 ± 1.8
97.6 ± 1.2
98.7 ± 1.3
102.6 ± 0.6
102.0 ± 0.9
103.1 ± 1.0
103.0 ± 0.9
95.5 ± 0.2
99.6 ± 0.3
102.3 + 0.6
102.1 ± 0.9
100.2 ± 0.3
(a) Three determinations per solution; 40% (W/W) methanol;
flow rate =1.0 mL/min.
261
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TABLE 4. RECOVERY OF ANALYTES FROM GROUNDWATER (LAKOTA HILLS) (a)
Mixture
A
B
C
D
E
F
Hg Analytes
Hg(H)
CH3Hg+
C2H5Hg+
C6H5Hg+
Hg(ii)
CH3Hg+
C2H5Hg*
C6H5Hg+
Hg(H)
CH3Hg*
C2H5Hg+
C6H5Hg*
Hg(ii)
CH3Hg+
C2H5Hg+
C6H5Hg+
Hg(ii)
CH3Hg+
C2H5Hg+
C6H5Hg+
Hg(ii)
CH3Hg+
C2H5Hg+
C6H5Hg+
Hg added
M9 L"1
50
50
50
50
70
70
70
70
90
90
90
90
120
120
120
120
150
150
150
150
200
200
200
200
Hg determined
M9 L'1
(mean ± s.d.)
38.5 ± 0.3
45.8 ± 0.0
51.9 ± 0.2
41.2 ± 0.4
58.1 ± 0.1
65.0 ± 3.5
64.5 ± 2.4
68.5 ± 0.8
72.9 ± 0.3
84.2 ± 3.0
85.8 ± 1.2
98.0 ± 1.8
99.8 ± 0.0
114.5 ± 1.9
115.4 ± 1.0
118.5 ± 1.0
143.9 ± 0.4
143.3 ± 0.9
144.9 ± 0.2
145.9 ± 0.7
200.1 ± 2.3
192.8 ± 1.3
190.1 ± 1.6
185.1 ± 1.2
Recovery, %
(mean + s.d.)
77.0 ± 0.6
91.6 ± 0.0
103.8 ± 0.4
82.4 ± 0.9
83.0 ± 0.2
92.9 ± 5.0
92.1 ± 3.5
97.9 ± 1.1
81.0 ± 0.3
93.6 ± 3.4
95.3 ± 1.3
100.0 ± 2.0
83.2 ± 0.0
95.4 ± 1.6
96.1 ± 0.8
98.8 ± 0.9
95.9 ± 0.2
95.5 ± 0.6
96.6 ± 0.1
97.3 ± 0.5
100.0 ± 1.1
96.4 ± 0.7
95.1 ± 0.8
92.6 ± 0.6
(a) Two determinations per solution; 40% (W/W) methanol;
flow rate =1.0 mL/min.
262
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TABLE 5. RECOVERY OF ANALYTES FROM GROUND WATER (CLERMONT COUNTY, OH)
AND TAP WATER (CINCINNATI, OH) (A)
Hg added
Mixture Hg Analytes
Hg measured
in groundwater
W L'1
(mean ± s.d.
Hg measured
in tap water
M9L'1
(mean ± s.d.)
Recovery, % Recovery, %
(mean ± s.d.) (mean ± s.d.)
A Hg(II)
CH3Hg+
C2H5Hg+
C6H5Hg+
B Hg(II)
CH3Hg+
C2H5Hg*
C6H5Hg+
C Hg(II+)
^t CH3ng
P C2H5Hg+
C6H5Hg+
D Hg(II)
CH3Hg+
C2H5Hg+
C6H5Hg+
50
50
50
50
100
100
100
100
120
120
120
120
150
150
150
150
52.3 ± 2.0
43.6 ± 2.0
42.7 ± 3.9
49.0 ± 2.3
98.6 ± 4.0
93.3 ± 3.5
97.0 ± 2.6
94.9 ± 3.0
120.1 ± 0.5
111.5 ± 1.3
109.4 ± 4.0
120.6 ± 0.4
—
—
— — —
49.5 ± 4.5
51.7 ± 3.3
44.8 ± 5.4
47.6 ± 4.6
100.7 ± 0.9
103.1 ± 1.9
88.0 ± 6.5
99.3 ± 0.8
—
—
—
—
150.5 ± 3.6
153.3 ± 2.4
129.5 ± 3.8
138.9 ± 2.0
104.6 ± 4.0
87.2 ± 4.3
85.4 ± 7.9
96.8 ± 4.5
98.6 + 4.0
93.3 ± 3.5
97.0 ± 2.6
94.9 ± 3.0
100.1 ± 0.4
92.9 ± 4.1
91.2 ± 3.5
100.5 ± 0.3
—
___
99.0 ± 9.0
103.4 ± 6.7
89.6 ±11.0
95.2 ± 9.1
101.9 ± 0.9
103.1 ± 1.9
88.0 ± 6.5
99.3 ± 0.8
—
—
—
—
100.3 ± 2.4
102.2 ± 1.6
86.3 + 2.6
92.6 ± 1.3
(a) Three determinations per solution; 60% (W/W) methanol, flow rate =1.0 mL/min.
263
-------
100-1
80 -
V)
60 -
c
CO
O
I
I 40
20 -
0 2
Retention Time (min.)
Figure 1. Separation of four charge-neutral mercury analytes.
Conditions: eluent, 60% (W/W) methane!, column, LiChrosorb RP-18 (5 pi), 25 x
0,46 cm; pH 5.5 acetate buffer; 0.01% (V/V) 2-ME; flow rate, 1.0 ml min'1;
standard mixture, 10 /zg ml/1 each analyte; sample loop, 100 pL. (1) Hgll; (2)
methylmercury; (3) ethylmercury; and (4) phenylmercury.
264
-------
265
-------
Stainless Steel
Screen and
Teflon Gasket
Rubber Stopper
To Vacuum
250 ml Reservoir
Clamp
1 Liter
Vacuum Flask
Figure 3. Sample and Mobile Phase Filtration Apparatus
266
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METHOD 245.5
DETERMINATION OF MERCURY IN SEDIMENTS
BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY
Edited by Larry B. Lobring and Billy B. Potter
Inorganic Chemistry Branch
Chemistry Research Division
Revision 2.3
April 1991
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
267
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METHOD 245.5
DETERMINATION OF MERCURY IN SEDIMENTS
BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY
1. SCOPE AND APPLICATION
1.1 This procedure1-2 measures total mercury (organic + inorganic) in
soils, sediments, bottom deposits and sludge type materials.
1.2 The range of the method is 0.2 to 5 /zg/g. The range may be
extended above or below the normal range by increasing or decreasing
sample size or by optimizing instrument sensitivity.
2. SUMMARY OF METHOD
2.1 A weighed portion of the sediment sample is transferred to a BOD
bottle (or equivalent flask fitted with a ground glass stopper) and
digested in aqua regia for 2 min at 95°C. The digested sediment
sample is diluted. Potassium permanganate is added to the sediment
sample. The BOD bottle is transferred to the water bath where the
sediment sample is oxidized for 30 min at 95°C. Mercury in the
digested sediment sample is reduced with stannous chloride to
elemental mercury and measured by the conventional cold vapor atomic
absorption technique.
2.2 An alternate digestion3 involving the use of an autoclave is
described in (Sect. 11.3).
3. DEFINITIONS
3.1 BIOCHEMICAL OXYGEN DEMAND (BOD) BOTTLE - BOD bottle, 300 ± 2 mL with
a ground glass stopper or an equivalent flask, fitted with a ground
glass stopper.
3.2 CALIBRATION BLANK - A volume of ASTM type II reagent water prepared
in the same manner (acidified) as the calibration standard.
CALIBRATION STANDARD (CAL) - A solution prepared from the mercury
stock standard solution used to calibrate the instrument response
with respect to analyte concentration.
INSTRUMENT DETECTION LIMIT (IDL) - The mercury concentration that
produces a signal equal to three times the standard deviation of the
blank signal.
LABORATORY FORTIFIED BLANK (LFB) - An aliquot of ASTM type II
reagent water to which known quantities of inorganic and/or organic
mercury are added in the laboratory. The LFB is analyzed exactly
3.3
3.4
3.5
268
-------
like a sample, and its purpose is to determine whether method
performance is within accepted control limits.
3.6 LABORATORY FORTIFIED SAMPLE MATRIX (LFM) - An aliquot of a sediment
sample to which known quantities of calibration standard 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 the
concentrations found.
3.7 LABORATORY REAGENT BLANK (LRB) - An aliquot of ASTM type II reagent
water that is treated exactly as a sample including exposure to all
glassware, equipment, and reagents used in analyses. The LRB is
used to determine if method analyte or other interferences are
present in the laboratory environment, reagents, or apparatus.
3.8 LINEAR DYNAMIC RANGE (LDR) - The concentration range over which the
analytical working curve remains linear.
3.9 METHOD DETECTION LIMIT (MDL) - The minimum concentration of mercury
that can be identified, measured and reported with 99% confidence
that the analyte concentration is greater than zero and determined
from analysis of seven LFMs.
3.10 QUALITY CONTROL SAMPLE (QCS) - A sediment sample containing known
concentration of mercury derived from externally prepared test
materials. The QCS is obtained from a source external to the
laboratory and is used to check laboratory performance.
3.11 SEDIMENT SAMPLE - A fluvial, sand and/or humic sample matrix exposed
to a marine, brackish or fresh water environment. It is limited by
this method to that portion which may be passed through a number
10 sieve or a 2 mm mesh sieve.
3.12 STOCK STANDARD SOLUTION - A concentrated mercury solution prepared
in the laboratory using assayed mercuric chloride or stock standard
solution purchased from a reputable commercial source.
4. 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. 10) must be
strictly followed.
4.2 Volatile materials which absorb at 253.7 nm will cause a positive
interference. In order to remove any interfering volatile
269
-------
materials, the dead air space in the BOD bottle should be purged
before addition of stannous chloride solution.
5. 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 practices4. 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 * 6.
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.
6. APPARATUS AND EQUIPMENT
6.1 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.
6.2 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 sediment sample in the BOD bottle.
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.
6.4 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. Instruments designed
specifically for mercury measurement using the cold vapor technique
are commercially available and may be substituted for the atomic
absorption spectrophotometer.
6.3
6.5 BIOCHEMICAL OXYGEN DEMAND (BOD) BOTTLE - See Sect.
3.1.
270
-------
6.6 DRYING TUBE - Tube (6-in. x 3/4-in. OD) containing 20 g of magnesium
perch!orate. The filled tube is inserted (in-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.
6.7 FLOWMETER - Capable of measuring an air flow of 1 L/min.
6.8 MERCURY HOLLOW CATHODE LAMP - Single element hollow cathode lamp or
electrodeless discharge lamp and associated power supply.
6.9 PYREX DISH - Any appropriate size, (8-in. x 8-in.) or (8-in. x 12-
in.).
6.10 RECORDER - Any multi-range variable speed recorder that is
compatible with the UV detection system is suitable.
6.11 SIEVE -/High-density polyethylene; polyester mesh, no. 10 mesh, 12-
in. Q.D and 3 1/2-in.; depth.
6.12 WATER BATH - The water bath should have a covered top and capacity
to sustain a water depth of 2-in. to 3-in. at 95°C ± 1°C. The
dimensions of the water bath should be large enough to accommodate
BOD bottles containing CAL, LFB, LFM, LRB, QCS and sediment samples
With the lid on.
REAGENTS AND CONSUMABLE MATERIALS
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. It is
recommended that the laboratory analyst assay all reagents for
mercury.
7.1.1 Hydrochloric Acid (HCL), concentrated (sp.gr. 1.19),
(CASRN 7647-01-0); assayed mercury level is not to exceed
1 ppb.
7.1.2 Hydroxylamine Hydrochloride (NH.OH-HCl), (CASRN 5470-11-1)
may be used in place of hydroxylamine sulfate (Sect. 7.6);
assayed mercury level of compound is not to exceed
0.05 ppm.
7.1.3 Hydroxylamine Sulfate [(NHgOHJ^H.SOJ (CASRN 10039-54-0);
assayed mercury level of compound is not to exceed
0.05 ppm.
7.1.4 Mercuric Chloride (HgCl2), (CASRN 7487-94-7).
271
-------
i (HN°3)' concentrated (sp.gr. 1.41), (CASRN
-37-2); assayed mercury level is not to exceed 1 ppb.
Potassium Permanganate (KMnOJ, (CASRN 7722-64-7); assayed
mercury level is not to exceed 0.05 ppm.
Reagent Water, ASTM type II.7
Sodium Chloride (NaCl), (CASRN 7647-14-5); assayed mercury
level is not to exceed 0.05 ppm.
Stannous Chloride (SnCl2'2H20), (CASRN 10025-69-1);
assayed mercury level is not to exceed 0.05 ppm.
Stannous Sulfate (SnS04), (CASRN 7488-55-3); assayed
mercury level is not to exceed 0.05 ppm.
7.1.5
7.1.6
7.1.7
7.1.8
7.1.9
7.1.10
7'1'11 7ciru«ic Acid (H2S04)> concentrated (sp.gr. 1.84), (CASRN
7664-93-9); assayed mercury level is not to exceed 1 ppb.
7.2 AQUA REGIA - Prepare immediately before use by carefully addina
three volumes of cone. HC1 (Sect. 7.1.1) to one volume of cone HNO,
(o6Ct. 7.1.5). •*
7.3 MERCURY CALIBRATION STANDARD - To each volumetric flask used for
serial dilutions, acidify with (0.1 to 0.2% by volume) HNO,
(Sect. 7.1.5). Using mercury stock standard (Sect. 7.4), make
serial dilutions to obtain a concentration of 0.1 ug Hq/mL This
standard should be prepared just before analyses.
7-4 UEKr?Y STOCK STANDARD - Dissolve in a 100-mL volumetric flask
0.1354 g HgCl, (Sect. 7.1.4) with 75 mL of reagent water (Sect.
7'5
of
-------
8. 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
contamination. All items used in the sample preparation should be
soaked in 30% HNO, (Sect. 7.1.5) and rinsed three times in reagent
water (Sect. 7.1.7).
8.2 The sediment sample should be preserved with nitric acid to an
approximate pH of 2.
8.3 Slowly decant the water from the settled sediment sample. Transfer
the sediment sample into a Pyrex tray and mix thoroughly with a
Teflon spatula. Discard sticks, stones, shells, living or dead
tissues and other foreign objects from the sediment sample.
8.4 Transfer the sediment from the Pyrex tray to a 10-mesh
(approximately 2-mm) sieve collecting the sediment sample in an
appropriate container. If enough sample has been collected, a
second container may be used for the percent wet weight
determination.
8.5 While the sample may be analyzed without drying, it has been found
to be more convenient to analyze a dry sample. Moisture may be
driven off in a drying oven at a temperature of 60°C. No mercury
losses have been observed by using this drying step. The dry sample
should be pulverized and thoroughly mixed before the aliquot is
weighed.
9. CALIBRATION AND STANDARDIZATION
9.1 Transfer 0.5, 1.0, 2.0, 5.0 and 10 ml aliquots of the 0.1 jug/mL CAL
(Sect. 7.3) to a series of 300-mL BOD bottles. These BOD bottles
will contain 0.5 to 1.0 /zg of Hg and are used to calibrate the
instrument.
9.2 To each of the BOD bottles add enough reagent water (Sect. 7.1.7) to
make a total volume of 10 ml. Add 5 mL of aqua regia (Sect. 7.2)
immediately cap and cover the top of the BOD bottle with aluminum
foil or other appropriate cover.
9.3 Construct a standard curve by plotting peak height or maximum
response of the standards (obtained in Sect. 11.7) versus micrograms
of mercury contained in the bottles. The standard curve should
comply with Sect. 10.2.3. Calibration using computer or calculator
based regression curve fitting techniques on concentration/response
data is acceptable.
273
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10.2.2
10. QUALITY CONTROL
10>1 S-labora+°7 /n^9 this method is ™Wired to operate a formal
quality control (QC) program. The minimum requirements of this
program consist of an initial demonstration of laboratory capa-
bility by analyses of laboratory reagent blanks, fortified blanks
and samples used for continuing check on method performance.
Standard Reference Materials (SRMs)8- 9- 10 are available and
should be used to validate laboratory performance. Commercially
available sediment reference materials are acceptable for routine
vTn£! !3[ SSS'*.^laboratory is required to maintain performance
records that define the quality of the data generated.
10.2 INITIAL DEMONSTRATION OF PERFORMANCE.
10.2.1 The initial demonstration of performance is used to
characterize instrument performance (MDLs and linear
calibration ranges) for analyses conducted by this method.
A mercury MDL should be established using LFM at a
concentration of two to five times the estimated detection
limit . To determine MDL values, take seven replicate
aliquots of the LFM 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 is, t = 3.14 for seven
replicates.
S = standard deviation of the replicate analyses.
A MDL should be determined every six months or whenever a
significant change in background or instrument response is
expected (e.g., detector change).
Linear calibration ranges - The upper limit of the linear
calibration range should be established for mercury 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. Linear
calibration ranges should be determined every six months
or whenever a significant change in instrument response is
observed.
10.3 ASSESSING LABORATORY PERFORMANCE - REAGENT AND FORTIFIED BLANKS
10.2.3
274
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10.3.1 The laboratory must analyze at least one LRB (Sect. 3.7)
with each set of samples. LRB data are used to assess
contamination from the laboratory environment and to
characterize spectral background from the reagents used in
sample processing. If a mercury value in a LRB exceeds
its determined MDL, then laboratory or reagent
contamination is suspect. Any determined source of
contamination should be eliminated and the samples
reanalyzed.
10.3.2 The laboratory must analyze at least one LFB (Sect. 3.5)
with each batch of samples. Calculate accuracy as percent
recovery (Sect. 10.4.2). If recovery of mercury falls
outside control limits (Sect. 10.3.3), the method is
judged out of control. The source of the problem should
be identified and resolved before continuing analyses.
10.3.3 Until sufficient data (usually a minimum of 20 to 30
analyses) become available, each laboratory should assess
its performance against recovery limits of 85-115%. When
sufficient internal performance data become 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
After each five to ten new recovery measurements, new
control limits should be calculated using only the most
recent 20 to 30 data points.
10.4 ASSESSING ANALYTE RECOVERY - LABORATORY FORTIFIED SAMPLE MATRIX
10.4.1 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. Select a sediment sample that is
representative of the type of sediment being analyzed and
has a low mercury background. It is recommended that this
sample be analyzed prior to fortification. The
fortification should be 20% to 50% higher than the
analyzed value. Over time, samples from all routine
sample sources should be fortified.
10.4.2 Calculate the percent recovery, corrected for background
concentrations measured in the unfortified sample, and
compare these values to the control limits established in
Sect. 10.3.3 for the analyses of LFBs. A recovery
calculation is not required if the concentration of the
analyte added is less than 10% of the sample background
concentration. Percent recovery may be calculated in
275
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units appropriate to the matrix, using the following
equation: 3
R
CS-C
x 100
where, R
I-
s
percent recovery
fortified sample concentration
sample background concentration
concentration equivalent of
fortifier added to sediment sample,
10.4.3
If mercury recovery falls outside the designated range,
and the laboratory performance is shown to be in control
(beet. 10.3) the recovery problem encountered with the
fortified sediment 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
11. PROCEDURE
°f dry sample and Place in bo«om of a BOD
(Sect 7 ^ Water (56Ct' 7'L7) and 5 mL of aa.ua
hntti -JI* I'2) ! """^lately cap and cover the top of the BOD
bottle with aluminum foil or other appropriate cover. Optionally a
s^v^tTAh033!? t0 3'4 9 ma£ be Used to adJust ^e respon e to
stay within the linear range of the standards.
11.2 Mix thoroughly, and place in the water bath for 2 min at 95<>C.
11.3 Remove the BOD bottles and allow to cool. Add 50 ml reagent water
1
are
are
emP1oyin9 an autoclave may also be
cone' Him rrt 7i L0n,C' H2S04 (Sect" 7-1-11> and 2 «"- °
cone. HN03 (Sect. 7.1.5) are added to 0.2 g sediment sample. Then
BoS hnLSat"rated P;ta??,lum Permanganate solution is added and the
BOD bottle is capped with a piece of aluminum foil. The samples a
then autoclaved at 121-C/15 psi. for 15 min. samples a
11.4 Turn on the spectrophotometer and circulating pump. Adiust the
?0 1 L/min' A11°W the sPect™Photomete? and pump to
B°D b°UleS t0 r°°m temPerature and dilute in the following
276
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11.5.1 To BOD bottles containing the instrument calibration
standards laboratory fortified blank (LFB) and laboratory
reagent blank (LRB) add 50 ml of reagent water
(Sect. 7.1.7).
11.5.2 To BOD bottles containing the sediment samples, quality
control sample (QCS) and laboratory fortified sample
matrix (LFM) add 55 ml of reagent water (Sect. 7.1.7).
11.6 To each BOD bottle, add 6 ml of NaCl-(NH2OH)2'H2S04 (Sect. 7.6) to
reduce the excess permanganate.
11.7 Treating each bottle individually:
11.7.1 Placing the aspirator inside the BOD bottle and above the
liquid, purge the head space (20 to 30 sec) to remove
possible gaseous interferents.
11.7.2 Add 5 ml of SnCl2 solution (Sect. 7.7) and immediately
attach the bottle to the aeration apparatus.
11.7.3 The absorbance, as exhibited either on the
spectrophotometer or the recorder, will increase and reach
maximum within 30 sec. As soon as the recorder pen levels
off, approximately 1 min, open the bypass value (or
optionally remove aspirator from the BOD bottle if it is
vented under the hood) and continue the aeration until the
absorbance returns to its minimum value.
11.8 Close the bypass value, remove the aspirator from the BOD bottle and
continue the aeration. Repeat step (Sect. 11.7) until all BOD
bottles have been aerated and recorded.
12. CALCULATIONS
12.1 Measure the peak height of the unknown from the chart and read the
mercury value from the standard curve.
12.2 Calculate the mercury concentration in the sample by the formula:
ir I - V-9 H& i-n the aliquot
ng/g -
Qf the a2iqu0t in grams
12.3 Report mercury concentrations as follows: Below 0.1 Mg/9.
< 0.1 Mg/g; between 0.1 and 1 ng/g, to the nearest 0.01 pg; between
1 and 10 M9/9, to nearest 0.1 M9; above 10 jug/g, to nearest M9-
277
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13. PRECISION AND ACCURACY
13.1 The standard deviation for mercury in sediment samples are reported
mi h«? S™ ^ 5^g a"d 0.82 ± 0.03 jig Hg/g with recoveries for
LFM being 97% and 94% respectively. These sediment samples were
fortified with methyl mercuric chloride.
Hu^lirLassurance data for the sediment survey was contributed by
U.S. EPA, Environmental Research Laboratory - Duluth. See Table 1.
9.
10.
14. REFERENCES
2.
3.
4.
5.
6.
7.
8.
"' °ntari° water
Glass, G.E.; Sorensen, J.A.; Schmidt, K.W.; Rapp Jr., G.R.; "New
Source Identification of Mercury Contamination in the Great Lakes"
Envion. Sci. and Techno!.. Vol. 24, No. 7, 1990. '
Salma, M., private communication, EPA Cal/Nev Basin Office, Almeda,
California. '
"Safety in Academic Chemistry Laboratories", American Chemical
1979 Publlcatlon' Committee on Chemical Safety, 3rd Edition,
"OSHA Safety and Health Standards, General Industry", (29CFR 1910)
Occupational Safety and Health Administration, OSHA 2206, revised
January, 1976.
"Proposed OSHA Safety and Health Standards, Laboratories"
Occupational^Safety and Health Administration, Federal Register,
"Specification for Reagent Water", D1193, Annual Book of ASTM
Standards, Vol. 11.01, 1990.
National Institute of Standards and Technology, Office of Standards
VIST?£^ aT6rialr; Gaithel"sburg, MD 20899: Estuarine Sediment
(SRM 1646), Trace Elements in a Calcerous Loam Soil (CRM 8032),
IS SS:!^.!:!!^8^^!.!?1?,???3). T«« El-ents in
in Sewer Sludge-
12201
National Research Council of Canada, Marine Analytical Chemistry
Standards Program, Division of Chemistry, Montreal Road, Ottawa
Ontario K1A OR9,. Canada: Marine Sediments (BCSS-1, MESS-1, and
rALb—l ) .
11. Code of Federal Regulations 40, Ch. 1, Pt. 136 Appendix B.
278
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TABLE 1. QUALITY ASSURANCE SUMMARY FOR 15 SEDIMENT ANALYSES
IQfift SURVEY OF MINNESOTA LAKES1' z.
Number of Samples or
Parameter Value Sample Pairs
Detection Limit in Flask3
(ng Hg/L) 6.6 471
Precision (ng Hg/L)
Lab
Field
Bias (%)
Spike Recovery (%)
Loss on Drying (%)
27
26
-2
100 + 7
5.3 + 1.0
29
96
30
27
72
1 Data were furnished by Gary Glass, U.S. EPA, Environmental Research
Laboratory - Duluth, Minnesota 55804, and John A. Sorensen, College of Science
and Engineering, University of Minnesota, Duluth, Minnesota 55812.
2 The analytical instrument used to achieve the precision and accuracy
included: Perkin Elmer atomic absorption spectrophotometers (Model 403 and
5000) equipped with deuterium background correctors, electrodeless discharge
lamp (ME-782) and power supply (APR), and Heath Schlumberger (SR-206) chart
recorder. A slit width of 1 mm (spectral band with 0.07 nm) was used at a
wavelength of 253.7 nm. The instruments were operated in the concentration
mode (10 x) with the integration set at 10 average (ten samples of the signal
are averaged as one value per second). The concentration readout of the
signal was recorded on the strip chart at 20 mv/25 cm chart width. The
elemental mercury analyte was circulated (1 L/min) through a (18 x 1.8 cm)
cylindrical absorption cell using a Neptune Dyna Pump. After the atomic
absorption resulting from the presence of mercury vapor reached a maximum in
about 0.5-1.0 min, the pump was turned off and the absorption peak climbed to
its final value.
3 Long, G.L.; Winefordner, J.D.; Anal. Chem. 1983, Vol. 55: 712A-724A.
279
-------
BUBBLER
SAMPLE SOLUTION
IN BOO BOTTLE
ABSORPTION
CELL
SCRUBBER
CONTAINING
A MERCURY
ABSORBING
MEDIA
Flgurt 1. Apparatus for Flaneless Mercury Determination
Because of the toxic nature of mercury vapor, inhalation must be avoided.
SS3 ?£?' a byEa" hp been Included in the system to either vent the mercury
vapor into a exhaust hood or pass the vapor through some absorbing media, such
as: a) equal volumes of 0.1 N KMnO, and 10% H,S P<°' B°X 2526> Columbus« OH «216. Catalog No! 580-
280
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METHOD 245.6
DETERMINATION OF MERCURY IN TISSUES
BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY
Edited by Larry B. Lobring and Billy B. Potter
Inorganic Chemistry Branch
Chemistry Research Division
Revision 2.3
April 1991
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
281
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METHOD 245.6
DETERMINATION OF MERCURY IN TISSUES
BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY
SCOPE AND APPLICATION
1.1 This procedure measures total mercury (organic + inorganic) in
biological tissue samples.
1.2 The range of the method is 0.2 to 5 /ug/g. The range may be extend-
ed above or below the normal range by increasing or decreasing
sample size or by optimizing instrument sensitivity.
SUMMARY OF METHOD
2.1
A weighed portion of the tissue sample is digested with sulfuric and
nitric acid at 58°C followed by overnight oxidation with potassium
permanganate and potassium persulfate at room temperature. Mercury
in the digested sample is reduced with stannous chloride to
elemental mercury and measured by the conventional cold vapor atomic
absorption technique.
DEFINITIONS
3.1
3.2
3.3
3.4
3.5
3.6
BIOCHEMICAL OXYGEN DEMAND (BOD) BOTTLE - BOD bottle, 300 ± 2 mL with
a ground glass stopper or an equivalent flask, fitted with a ground
glass stopper.
CALIBRATION BLANK - A volume of ASTM type II reagent water prepared
in the same manner (acidified) as the calibration standard.
CALIBRATION STANDARD (CAL) - A solution prepared from the mercury
stock standard solution used to calibrate the instrument response
with respect to analyte concentration.
INSTRUMENT DETECTION LIMIT (IDL) - The mercury concentration that
produces a signal equal to three times the standard deviation of the
blank signal.
LABORATORY FORTIFIED BLANK (LFB) - An aliquot of ASTM type II
reagent water to which known quantities of inorganic and/or organic
mercury are added in the laboratory. The LFB is analyzed exactly
like a sample, and its purpose is to determine whether method
performance is within accepted control limits.
LABORATORY FORTIFIED SAMPLE MATRIX (LFM) - A portion of a tissue
sample to which known quantities of calibration standard are added
in the laboratory. The LFM is analyzed exactly like a sample, and
its purpose is to determine whether the sample matrix contributes
282
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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 the
concentrations found.
3.7 LABORATORY REAGENT BLANK (LRB) - An aliquot of ASTM type II reagent
water that is treated exactly as a sample including exposure to all
glassware, equipment, and reagents used in analyses. The LRB is
used to determine if method analyte or other interferences are
present in the laboratory environment, the reagents or apparatus.
3.8 LINEAR DYNAMIC RANGE (LDR) - The concentration range over which the
analytical working curve remains linear.
3.9 METHOD DETECTION LIMIT (MDL) - The minimum concentration of mercury
that can be identified, measured and reported with 99% confidence
that the analyte concentration is greater than zero and determined
from analysis of laboratory fortified tissue sample matrix (LFM).
3.10 QUALITY CONTROL SAMPLE (QCS) - A tissue sample containing known
concentration of mercury derived from externally prepared test
materials. The QCS is obtained from a source external to the
laboratory and is used to check laboratory performance.
3.11 TISSUE SAMPLE - A biological sample matrix exposed to a marine,
brackish or fresh water environment. It is limited by this method
to the edible tissue portion.
3.12 STOCK STANDARD SOLUTION - A concentrated solution containing mercury
prepared in the laboratory using assayed mercuric chloride or stock
standard solution purchased from a reputable commercial source.
4. 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. 10) must be
strictly followed.
4.2 Volatile materials 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 BOD bottle should be purged
before the addition of stannous chloride solution.
4.3 Interferences associated with the tissue matrix are corrected for in
calibration procedure (Sect. 9).
283
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SAFETY
5.1
5.2
5.3
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 practices1. 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 ?' 3.
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.
All personnel handling tissue samples should beware of biological
hazards associated with tissue samples. Bivalve mollusk may
concentrate toxins and pathogenic organisms. Tissue dissection
should be conducted in a bio-hazard hood and personnel should wear
surgical mask and gloves.
6. APPARATUS AND EQUIPMENT
6.1
6.2
6.3
6.4
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.
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 tissue sample in the BOD bottle.
AIR PUMP - Any pump (pressure or vacuum system) capable of passing
air at 1 L/min is used. Regulated compressed air can be used in an
open one-pass system.
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. Instruments designed
specifically for mercury measurement using the cold vapor technique
284
-------
are commercially available and may be substituted for the atomic
absorption spectrophotometer.
6.5 BIOCHEMICAL OXYGEN DEMAND (BOD) BOTTLE - See Sect. 3.1.
6.6 DRYING TUBE - Tube (6-in. x 3/4-in. OD) containing 20 g of magnesium
perchlorate. The filled tube is inserted (in-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.
This avoids water condensation in the cell.
6.7 FLOWMETER - Capable of measuring an air flow of 1 L/min.
6.8 MERCURY HOLLOW CATHODE LAMP - Single element hollow cathode lamp or
electrodeless discharge lamp and associated power supply.
6.9 RECORDER - Any multi-range variable speed recorder that is
compatible with the UV detection system is suitable.
6.10 WATER BATH - The water bath should have a covered top and capacity
to sustain a water depth of 2-in. to 3-in. at 95°C ± 1°C. The
dimensions of the water bath should be large enough to accommodate
BOD bottles containing CAL, LFB, LFM, LRB, QCS and tissue samples
with the lid on.
REAGENTS AND CONSUMABLE MATERIALS
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.
7.1.1 Hydroxylamine Hydrochloride (NHpOH'HCl), (CASRN 5470-11-1)
may be used in place of hydroxyI amine sulfate in Sect.
7.6. The assayed mercury level of either compound is not
to exceed 0.05 ppm.
7.1.2 Hydroxylamine Sulfate [(NH2OH)2'H2S04] (CASRN 10039-54-0);
assayed mercury level is not to exceed 1 ppb.
7.1.3 Mercuric Chloride (HgCl2), (CASRN 7487-94-7).
7.1.4 Nitric Acid (HN03), concentrated (sp.gr. 1.41), (CASRN
7697-37-2); assayed mercury level is not to exceed 1 ppb.
7.1.5 Potassium Permanganate (KMn04), (CASRN 7722-64-7); assayed
mercury level is not to exceed 0.05 ppm.
7.1.6 Potassium Persulfate (K2S208), (CASRN 7727-21-1); assayed
mercury level is not to exceed 0.05 ppm.
7.1.7 Reagent Water, ASTM type II.4
285
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7.1.8
7.1.9
7.1.10
7.1.11
Sodium Chloride (NaCl), (CASRN 7647-14-5); assayed mercury
level is not to exceed 0.05 ppm.
Stannous Chloride (SnCl2'2H20), (CASRN 10025-69-1);
assayed mercury level is not to exceed 0.05 ppm.
Stannous Sulfate (SnSOJ, (CASRN 7488-55-3); assayed
mercury level is not to exceed 0.05 ppm.
Sulfuric Acid (H2S04), concentrated (sp.gr. 1.84), (CASRN
7664-93-9); assayed mercury level is not to exceed 1 ppb.
7.2 MERCURY CALIBRATION STANDARD - To each volumetric flask used for
serial dilutions, acidify with (0.1 to 0.2% by volume) HNO,
(Sect. 7.1.4). Using mercury stock standard (Sect. 7.3), make
serial dilutions to obtain a concentration of 0.1 /ig Hg/mL. This
standard should be prepared just before analyses.
7.3 MERCURY STOCK STANDARD - Dissolve in a 100-mL volumetric flask
0.1354 g HgCl2 (Sect. 7.1.3) with 75 mL of reagent water
(Sect. 7.1.7). Add 10 ml of cone. HNO, (Sect. 7.1.4) and dilute to
mark. Concentration is 1.0 mg Hg/mL.
7.4 POTASSIUM PERMANGANATE SOLUTION - Dissolve 5 g of KMnO,
(Sect. 7.1.5) in 100 mL of reagent water (Sect. 7.1.7)!
7.5 POTASSIUM PERSULFATE SOLUTION - Dissolve 5 g of K,S,0« (Sect. 7 1 6)
in 100 mL of reagent water (Sect. 7.1.7).
7.6 SODIUM CHLORIDE-HYDROXYLAMINE SULFATE SOLUTION - Dissolve 12 g of
NaCl (Sect. 7.1.8) and 12 g of (NH,OH)2-H,SO, (Sect. 7.1.2) or 12 q
of NH-.OH-HC1 (Sect. 7.1.1) dilute with reagent water (Sect. 7.1.7)
to 100 mL.
7.7 STANNOUS CHLORIDE SOLUTION - Add 25 g SnCl2'2H?0 (Sect. 7.1 9) or
25 g of SnS04 to 250 mL of 0.5 N H,SOA (Sect. 7.8). This mixture is
a suspension and should be stirrecf continuously during use.
7.8 SULFURIC ACID, 0.5 N - Slowly add 14.0 mL of cone. H,SO,
(Sect. 7.1.10) dilute to 1 L with reagent water (Sect. 7.1.7).
8. 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 contact or airborne mercury
contamination.
286
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8.2 The tissue sample should be preserved and dissected in accordance
with Method 200.3, "Sample Preparation Procedure for Spectrochemical
Determination of Total Recoverable Elements in Biological Tissues",
only Sect. 8. Tissue Dissection, is used in this method.
8.3 Weigh 0.2- to 0.3-g portions of each sample and place in the bottom
of a dry BOD bottle. Care must be taken that none of the sample
adheres to the side of the bottle. Immediately cap and cover the
top of the BOD bottle with aluminum foil.
9. CALIBRATION AND STANDARDIZATION
9.1 The calibration curve is prepared from values determined for
portions of fortified tissue treated in the manner used for the
tissue samples being analyzed. For preparation of the calibration
standards, blend a portion of tissue in a Waring blender.
9.2 Transfer accurately weighed portions to each of five dry BOD
bottles. Each sample should weigh about 0.2 g. Add 4 ml of cone.
H2SO, and 1 ml of cone. HN03 to each bottle and place in a water
bath maintained at 58°C until the tissue is completely dissolved (30
to 60 minutes).
9.3 Cool and transfer 0.5, 2.0, 5.0 and 10.0 ml aliquots of the CAL
(Sect. 7.2) solution containing 0.5 to 1.0 p.g of Hg to the BOD
bottles containing tissue. Cool to 4°C in an ice bath and
cautiously add 15 ml of potassium permanganate solution (Sect. 7.4)
and 8 ml of potassium persulfate (Sect. 7.5). Allow to stand
overnight at room temperature under oxidizing conditions.
9.4 Construct a standard curve by plotting peak height or maximum
response of the standard (obtained in Sect. 11.7) versus micrograms
of mercury contained in the bottles. The standard curve should
comply with Sect. 10.2.3. Calibration using computer or calculator
based regression curve fitting techniques on concentration/response
data is acceptable.
10. QUALITY CONTROL
10.1 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 analyses of laboratory reagent blanks, fortified blanks and
samples used for continuing check on method performance. Standard
Reference Materials (SRMs)5' are available and should be used to
validate laboratory performance. Commercially available tissue
reference materials are acceptable for routine laboratory use. The
laboratory is required to maintain performance records that define
the quality of data generated.
287
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10.2 INITIAL DEMONSTRATION OF PERFORMANCE
10.2.1 The initial demonstration of performance is used to
characterize instrument performance (MDLs and linear
calibration ranges) for analyses conducted by this method.
10.2.2 A mercury MDL should be established using LFM at a
concentration of two to five times the estimated detection
limit'. To determine MDL values, take seven replicate
aliquots of the LFM 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.
A MDL should be determined every six months or whenever a
significant change in background or instrument response is
expected (e.g., detector change).
10.2.3 Linear calibration ranges - The upper limit of the linear
calibration range should be established for mercury 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. Linear calibration
ranges should be determined every six months or whenever a
significant change in instrument response is observed.
10.3 ASSESSING LABORATORY PERFORMANCE - REAGENT AND FORTIFIED BLANKS
10.3.1 The laboratory must analyze at least one LRB (Sect. 3.7)
with each set of samples. LRB data are used to assess
contamination from the laboratory environment and to
characterize spectral background from the reagents used in
sample processing. If an mercury value in a LRB exceeds
its determined MDL, then laboratory or reagent
contamination is suspect. Any determined source of
contamination should be corrected and the samples
reanalyzed.
10.3.2 The laboratory must analyze at least one LFB (Sect. 3.5)
with each batch of samples. Calculate accuracy as percent
recovery (Sect. 10.4.2). If the recovery of mercury falls
outside control limits (Sect. 10.3.3), the method is
288
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judged out of control. The source of the problem should
be identified and resolved before continuing analyses.
10.3.3 Until sufficient data (usually a minimum of 20 to 30
analyses) become available, each laboratory should assess
its performance against recovery limits of 85-115%. When
sufficient internal performance data become 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
After each five to ten new recovery measurements, new
control limits should be calculated using only the most
recent 20 to 30 data points.
10.4 ASSESSING ANALYTE RECOVERY - LABORATORY FORTIFIED SAMPLE MATRIX
10.4.1 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. Select a tissue sample that is
representative of the type of tissue being analyzed and
has a low mercury background. It is recommended that this
sample be analyzed prior to fortification. The
fortification should be 20% to 50% higher than the
analyzed value. Over time, samples from all routine
sample sources should be fortified.
10.4.2 Calculate the percent recovery, corrected for background
concentrations measured in the unfortified sample, and
compare these values to the control limits established in
Sect. 10.3.3 for the analyses of LFBs. A recovery
calculation is not required if the concentration of the
analyte added is less than 10% of the sample background
concentration. Percent recovery may be calculated in
units appropriate to the matrix, using the following
equation:
Cs - C
R = x 100
where, R = percent recovery
Cs = fortified sample concentration
C = sample background concentration
s = concentration equivalent of
fortifier added to tissue sample.
289
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10.4.3
If mercury recovery falls outside the designated range,
and the laboratory performance is shown to be in control
(Sect. 10.3), the recovery problem encountered with the
fortified tissue 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.
11. PROCEDURE
11.1 Add 4 ml of cone. H2SO, (Sect. 7.1.10) and 1 mL of cone. HNO,
(Sect. 7.1.4) to each Tpottle and place in a water bath maintained at
58°C until the tissue is completely dissolved (30 to 60 min).
11.2 Cool to 4°C in an ice bath and cautiously add 5 ml of potassium
permanganate solution (Sect. 7.4) in 1 ml increments. Add an
additional 10 ml or more of permanganate, as necessary to maintain
oxidizing conditions. Add 8 mL of potassium persulfate solution
(Sect. 7.5). Allow to stand overnight at room temperature.
As an alternative to the overnight digestion, tissue solubilization
may be carried out in a water bath at 80°C for 30 min. The sample
is cooled and 15 mL of potassium permanganate solution (Sect. 7.4)
added cautiously followed by 8 mL of potassium persulfate solution
(Sect. 7.5). At this point, the sample is returned to the water
bath and digested for an additional 90 min at 30°C. Calibration
standards are treated in the same manner.
11.3 Turn on the spectrophotometer and circulating pump. Adjust the pump
rate to 1 L/min. Allow the spectrophotometer and pump to stabilize.
11.4 Cool the BOD bottles to room temperature and dilute in the following
manner:
11.4.1
11.4.2
To each BOD bottle containing the CAL, LFB and LRB, add 50
mL of reagent water (Sect. 7.1.7).
To each BOD bottle containing a tissue sample, QCS or LFM,
add 55 mL of reagent water (Sect. 7.1.7).
11.5 To each BOD bottle, add 6 mL of sodium chloride-hydroxylamine
sulfate solution (Sect. 7.6) to reduce the excess permanganate.
11.6 Treating each bottle individually:
11.6.1
11.6.2
Placing the aspirator inside the BOD bottle and above the
liquid, purge the head space (20 to 30 sec) to remove
possible gaseous interferents.
Add 5 mL of stannous chloride solution (Sect. 7.7) and
immediately attach the bottle to the aeration apparatus.
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11.6.3 The absorbance, as exhibited either on the spectro-
photometer or the recorder, will increase and reach
maximum within 30 sec. As soon as the recorder pen levels
off, approximately 1 min, open the bypass value (or
optionally remove aspirator from the BOD bottle if it is
vented under the hood) and continue the aeration until the
absorbance returns to its minimum value.
11.7 Close the bypass value, remove the aspirator from the BOD bottle and
continue the aeration. Repeat step (Sect. 11.6) until all BOD
bottles have been aerated and recorded.
12. CALCULATIONS
12.1 Measure the peak height of the unknown from the chart and read the
mercury value from the standard curve.
12.2 Calculate the mercury concentration in the sample by the formula:
Hal a = _ W Hg in the
* * wt. of the aliquot in grams
12.3 Report mercury concentrations as follows: Below 0.1 jug/g, <
0.1 M9/g; between 0.1 and 1 M9/9> to the nearest 0.01 /ug; between 1
and 10 p,g/g, to nearest 0.1 jug; above 10 jug/g, to nearest /ug.
13. PRECISION AND ACCURACY
13.1 The standard deviation for mercury in fish tissue samples are
reported as 0.19 ± 0.02 #g Hg/g , 0.74 ± 0.05 fig Hg/g and 0.74 ±
0.05 tig Hg/g with recoveries for LFM being 112%, 93%, and 86%,
respectively. These tissue samples were fortified with methyl
mercuric chloride.
14. REFERENCES
1. "Safety in Academic Chemistry Laboratories", American Chemical
Society Publication, Committee on Chemical Safety, 3rd Edition,
1979.
2. "OSHA Safety and Health Standards, General Industry", (29CFR 1910),
Occupational Safety and Health Administration, OSHA 2206, revised
January, 1976.
3. "Proposed OSHA Safety and Health Standards, Laboratories",
Occupational Safety and Health Administration, Federal Register,
July 24, 1986.
4. "Specification for Reagent Water," Annual Book of ASTM Standards,
D1193, Vol. 11.01, 1990.
291
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5. National Institute of Standards and Technology, Office of Standards
Reference Materials, Gaithersburg, MD 20899: Aquatic Plant -
Lagarosiphon major (CRN 8030), Aquatic Plant - Platihypnidium
riparioides (CRM 8031), Oyster Tissue (SRM 1566a), Albacore Tuna
(RM 50).
6. National Research Council of Canada, Marine Analytical Chemistry
Standards Program, Division of Chemistry, Montreal Road, Ottawa,
Ontario K1A OR9, Canada: Dogfish Liver (DOLT-1), Dogfish Muscle
(DORM-1), Non Defatted Lobster Hepatopancreas (LUTS-1), Lobster
Hepatopancreas (TORT-1).
7. Code of Federal Regulations 40, Ch. 1, Pt. 136 Appendix B.
292
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O* BUBBLER
ABSORPTION
CELL
SAMPLE SOLUTION
IN BOO BOTTLE
SCRUBBER
CONTAINING
A MERCUR*
ABSORBMG
MEDIA
Figurt 1. Apparatus for Flaaeltss Mercury Determination
Because of the toxic nature of mercury vapor, inhalation must be avoided.
Therefore, a bypass has been Included 1n the system to either vent the mercury
vapor Into a exhaust hood or pass the vapor through some absorbing media, such
as: a) equal volumes of O.i N KMn04 and 10% H2SO,
b) 0.25% Iodine in a 3% KI 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.
293
•U.S. Government Printing Office: 1991— 54S-187/40551
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