Method 200.10 Determination of Trace Elements in Marine Waters by On-Line Chelation Preconcentration and Inductively Coupled Plasma


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
Chemical Exposure Research Branch
Human Exposure Research Division
Revision 1.6
September 1997
Edited by
John T. Creed
National Exposure Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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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
1.0	Scope and Application
1.1	This method describes procedures for
preconcentration and determination of total recoverable
trace elements in marine waters, including estuarine
water, seawater, and brines.
1.2	Acid solubilization is required prior to the
determination of total recoverable elements to facilitate
breakdown of complexes or colloids that 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:
Chemical Abstracts Service
Element	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
1.4	Method detection limits (MDLs) for these ele-
ments will be dependent on the specific instrumentation
employed and the selected operating conditions. How-
ever, the MDLs should be essentially independent of the
matrix because elimination of the matrix is a feature of
the method. Reagent water MDLs, which were deter-
mined using the procedure described in Section 9.2.4,
are listed in Table 1.
1.5	A minimum of 6-months experience in the use of
commercial instrumentation for inductively coupled
plasma mass spectrometry (ICP-MS) is recommended.
2.0	Summary of Method
2.1	This method is used to preconcentrate trace
elements using an iminodiacetate functionalized chelating
resin.12 Following acid solubilization, the sample is
buffered prior to the chelating column using an on-line
system. Groups 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.
2.2 The determinative step in this method is ICP-
MS.35 Sample material in solution is introduced by
pneumatic nebulization into a radio frequency 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 continuous dynode elec-
tron multiplier or Faraday detector and the ion information
is processed by a data handling system. Interferences
relating to the technique (Section 4) must be recognized
and corrected. Such corrections must include
compensation for isobaric elemental interferences and
interferences from polyatomic ions derived from the
plasma gas, reagents or sample matrix. Instrumental drift
must be corrected for by the use of internal standard-
ization.
3.0	Definitions
3.1	Calibration Blank (CB) - A volume of reagent
water fortified with the same matrix as the calibration
standards but without the analytes, internal standards, or
surrogate analytes.
3.2	Calibration Standard (CAL) — A solution pre-
pared from the primary dilution standard solution or stock
standard solutions and the internal standards and surro-
gate analytes. The CAL solutions are used to calibrate the
instrument response with respect to analyte concen-
tration.
3.3	Instrument Detection Limit (IDL) - The mini-
mum quantity of analyte or the concentration equivalent
that gives an analyte signal equal to three times the
standard deviation of the background signal at the se-
lected wavelength, mass, retention time, absorbance line,
etc.
3.4	Instrument Performance Check Solution (IPC)
- A solution of one or more method analytes, surrogates,
internal standards, or other test substances used to
evaluate the performance of the instrument system with
respect to a defined set of criteria.
3.5	Internal Standard (IS) - A pure analyte(s) added
to a sample, extract, or standard solution in known
amount(s) and used to measure the relative responses
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of other method analytes and surrogates that are compo-
nents of the same sample or solution. The internal
standard must be an analyte that is not a sample compo-
nent.
3.6	Laboratory Fortified Blank (LFB) — An aliquot
of reagent water or other blank matrices to which known
quantities of the method analytes are added in the
laboratory. The LFB is analyzed exactly like a sample,
and its purpose is to determine whether the methodology
is in control and whether the laboratory is capable of
making accurate and precise measurements.
3.7	Laboratory Fortified Sample Matrix (LFM) - An
aliquot of an environmental sample to which known
quantities of the method analytes are added in the
laboratory. The LFM is analyzed exactly like a sample,
and its purpose is to determine whether the sample matrix
contributes bias to the analytical results. The background
concentrations of the analytes in the sample matrix must
be determined in a separate aliquot and the measured
values in the LFM corrected for background
concentrations.
3.8	Laboratory Reagent Blank (LRB) — An aliquot
of reagent water or other blank matrices that are treated
exactly as a sample including exposure to all glassware,
equipment, solvents, reagents, internal standards, and
surrogates that are used with other samples. The LRB is
used to determine if method analytes or other interfer-
ences are present in the laboratory environment, the
reagents, or the apparatus.
3.9	Linear Dynamic Range (LDR) — The absolute
quantity or concentration range over which the instrument
response to an analyte is linear.
3.10	Material Safety Data Sheet (MSDS) - Written
information provided by vendors concerning a chemical's
toxicity, health hazards, physical properties, fire, and
reactivity data including storage, spill, and handling
precautions.
3.11	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.
3.12	Quality Control Sample (QCS) - A solution of
method analytes of known concentrations that is used to
fortify an aliquot of LRB or sample matrix. The QCS is
obtained from a source external to the laboratory and
different from the source of calibration standards. It is
used to check laboratory performance with externally
prepared test materials.
3.13	Stock Standard Solution (SSS) — A concen-
trated solution containing one or more method analytes
prepared in the laboratory using assayed reference
materials or purchased from a reputable commercial
source.
3.14	Total Recoverable Analyte (TRA) — The
concentration of analyte determined to be in either a solid
sample or an unfiltered aqueous sample following
treatment by refluxing with hot dilute mineral acid(s) as
specified in the method.
3.15	Tuning Solution (TS) - A solution that is used to
adjust instrument performance prior to calibration and
sample analyses.
4.0	Interferences
4.1	Several interference sources may cause inaccu-
racies in the determination of trace elements by ICP-MS.
These are:
4.1.1	Isobaric elemental interferences - Are caused
by isotopes of different elements that form singly or
doubly charged ions of the same nominal mass-to-
charge ratio and that 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. The analytical isotopes recom-
mended for use with this method are listed in Table 1.
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 af-
fected by ion energy and quadrupole 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 that
have the same nominal mass-to-charge ratio as the
isotope of interest and that 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. 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.
4.1.4	Physical interferences — Are associated with the
physical processes that 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
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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. Internal standardization may be
effectively used to compensate for many physical
interference effects.6 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. Memory interferences from the che-
lating 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.
4.2	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.
4.3	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 pretreat-
ment is employed to improve analyte recovery and to
minimize adsorption, hydrolysis, and precipitation effects.
5.0	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 reason-
ably achievable. Each laboratory is responsible for
maintaining a current awareness file of OSHA regula-
tions regarding the safe handling of the chemicals
specified in this method.78 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 radio frequency
radiation in addition to intense UV radiation. Suitable
precautions should be taken to protect personnel from
such hazards.
5.3	The acidification of samples containing reactive
materials may result in the release of toxic gases, such
as cyanides or sulfides. Acidification of samples should be
performed in a fume hood.
5.4	All personnel handling environmental samples
known to contain or to have been in contact with human
waste should be immunized against known disease
causative agents.
5.5	It is the responsibility of the user of this method to
comply with relevant disposal and waste regulations. For
guidance see Sections 14.0 and 15.0.
6.0	Equipment and Supplies
6.1	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 ethylene
tetra-fluoroethylene (ETFE) 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 equiva-
lent) for delivering 1% nitric acid carrier solution; sample
pump (P4), peristaltic pump for loading sample loop.
6.1.5	Control valves — Inert double stack, pneumati-
cally 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 (HDPE), for holding eluent and
carrier reagents.
6.1.7	Tubing — High pressure, narrow bore, inert
tubing (e.g., Tefzel ETFE or equivalent) for interconnec-
tion 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 Spec-
trometer
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.
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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 interfer-
ences (e.g., polyatomic oxide species).
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.
6.2.5	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 di-
luted prior to analysis.
6.3	Labware — For the determination of trace
elements, contamination and loss are of critical concern.
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 han-
dling, 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 or (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
hr 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 HDPE, 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 jA. 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, accu-
rate to ± 0.01 g.
6.4.3	Hotplate — 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.
7.0	Reagents and Standards
7.1	Water — For all sample preparation and dilu-
tions, ASTM type I water (ASTM D1193) is required.
7.2	Reagents may contain elemental impurities that
might affect the integrity of analytical data. Because of
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 water. Add 65 mL (60 g) of 20% ammonium hydrox-
ide 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 nec-
essary. Cool and dilute to 1 L with ASTM type I water.
7.2.4	Ammonium acetate buffer 2M, pH 5.5 - Prepare
as for Section 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 P1, 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 contam-
inants 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) conc.
nitric acid to 1000-mL with ASTM type I water.
7.2.5.2	Nitric acid 1% — Dilute 10 mL conc. nitric acid to
1000 mL with ASTM type I water.
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7.2.5.3	Nitric acid (1+1) - Dilute 500 mL conc. nitric acid
to 1000-mL with ASTM type I water.
7.2.5.4	Nitric acid (1 +9) - Dilute 100 mL conc. nitric acid
to 1000-mL with ASTM type I water.
7.2.6 Oxalic aciddihydrate (CASRN 6153-56-6), 0.2M
- Dissolve 25.2 g reagent grade C2H204-2H20 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 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 plastic bottles. The following procedures may
be used for preparing standard stock solutions:
Note: Some metals, particularly those that form sur-
face oxides require cleaning prior to being
weighed. This may be achieved by pickling the
surface of the metal in acid. An amount in ex-
cess 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 ,ug 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 /ig 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 ,ug Cu:
Pickle copper metal in (1 +9) nitric acid to an exact weight
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 ^g In: Pickle
indium metal in (1+1) nitric acid to an exact weight 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 /ug Pb: Dis-
solve 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 jug Ni:
Dissolve 0.100 g nickel powder in 5 mL conc. nitric acid,
heating to effect solution. Cool and dilute to 100 mL with
ASTM type I water.
7.3.7	Scandium solution, stock 1 mL = 1000 /ug 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.
7.3.8	Terbium solution, stock 1 mL = 1000 ^g Tb:
Dissolve 0.1176 gTb407 in 5 mL conc. nitric acid, heating
to effect solution. Cool and dilute to 100 mL with ASTM
type I water.
7.3.9	Uranium solution, stock 1 mL = 1000 fig U:
Dissolve 0.2110 g U02(N03)2-6H20 (Do Not Dry) in 20
mL ASTM type I water. Add 2-mL (1+1) nitric acid and
dilute to 100-mL with ASTM type I water.
7.3.10	Vanadium solution, stock 1 mL = 1000 fjg 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.
7.3.11	Yttrium solution, stock 1 mL = 1000 ^g Y:
Dissolve 0.1270 g Y203 in 5 mL (1+1) nitric acid, heating
to effect solution. Cool and dilute to 100 mL with ASTM
type I water.
7.4	Multielement Stock Standard Solution - 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
impurities that might influence the accuracy of the
standard. Freshly prepared standards should be trans-
ferred to acid cleaned, new FEP or HDPE bottles for
storage and monitored periodically for stability. A
multielement stock standard solution containing the
elements, cadmium, cobalt, copper, lead, nickel, ura-
nium, and vanadium (1 mL = 10 //g) 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
multielement calibration standards should be prepared
weekly. Dilute the stock multielement 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 pig /L.
7.5	Blanks - Four 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. The laboratory fortified
blank is used to assess the recovery of the method
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analytes and the rinse blank is used between samples to
minimize memory from the nebulizer/spray chamber
surfaces.
7.5.1	Calibration blank - Consists of 1 % (v/v) nitric acid
in ASTM type I water (Section 7.2.5.2).
7.5.2	Laboratory reagent blank (LRB) — Must contain
all the reagents in the same volumes as used in process-
ing the samples. The LRB must be carried through the
entire sample digestion and preparation scheme.
7.5.3	Laboratory Fortified Blank (LFB) - To an aliquot
of LRB, add aliquots from the multielement stock stan-
dard (Section 7.4) to produce a final concentration of 10
,ug/L for each analyte. The fortified blank must be carried
through the entire sample pretreatment and analytical
scheme.
7.5.4	Rinse Blank (RB) — Is a 1% (v/v) nitric acid
solution that is delivered to the ICP-MS between samples
(Section 7.2.5.2).
7.6	Tuning Solution — This solution is used for
instrument tuning and mass calibration prior to analysis
(Section 10.2). The solution is prepared by mixing nickel,
yttrium, indium, terbium, and lead stock solutions (Sec-
tion 7.3) in 1% (v/v) nitric acid to produce a concentration
of 100 ^g/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	Instrument Performance Check (IPC) Solution
-- The IPC solution is used to periodically verify instru-
ment performance during analysis. It should be prepared
by combining method analytes at appropriate concentra-
tions to approximate the midpoint of the calibration curve.
The IPC solution should be prepared from the same
standard stock solutions used to prepare the calibration
standards and stored in a FEP bottle. Agency programs
may specify or request that additional instrument perfor-
mance check solutions be prepared at specified concen-
trations in order to meet particular program needs.
7.9	Internal Standards Stock Solution, 1 mL =
100 pig — Dilute 10-mL of scandium, yttrium, indium,
terbium, and bismuth stock standards (Section 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 (Method A,
Section 10.5), or dilute by an appropriate amount using
1% (v/v) nitric acid, if the internal standards are being
added by peristaltic pump (Method B, Section 10.5).
Note: Bismuth should not be used as an internal
standard using the direct addition method (Me-
thod A, Section 10.5) as it is not efficiently
concentrated on the iminodiacetate column.
8.0	Sample Collection, Preservation, and
Storage
8.1	Prior to the collection of an aqueous sample,
consideration should be given to the type of data re-
quired, so that appropriate preservation and pretreatment
steps can be taken. Acid preservation should be per-
formed at the time of sample collection or as soon
thereafter as practically possible. The pH of all aqueous
samples must be tested immediately prior to aliquoting
for analysis to ensure the sample has been properly
preserved. If properly acid preserved, the sample can be
held up to 6 months before analysis.
8.2	For the determination of total recoverable
elements in aqueous samples, acidify with (1+1) nitric
acid (high purity) at the time of collection to pH<2;
normally, 3 mL of (1+1) acid per liter of sample is
sufficient for most 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 limita-
tions or transport restrictions, or are >pH2
because of high alkalinity should be acidified
with nitric acid to pH<2 upon receipt in the
laboratory. Following acidification, the sample
should be held for 16 h and the pH verified to be
<2 before withdrawing an aliquot for sample
processing.
8.3	For aqueous samples, a field blank should be
prepared and analyzed as required by the data user. Use
the same container and acid as used in sample collec-
tion.
9.0	Quality Control
9.1	Each laboratory using this method is required to
operate a formal quality control (QC) program. The
minimum requirements of this program consist of an
initial demonstration of laboratory capability and the
periodic analysis of laboratory reagent blanks, fortified
blanks and other laboratory solutions as a continuing
check on performance. The laboratory is required to
maintain performance records that define the quality of
the data generated.
9.2	Initial Demonstration of Performance (Manda-
tory)
9.2.1 The initial demonstration of performance is used
to characterize instrument performance (determination of
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linear dynamic ranges and analysis of quality control
samples) and laboratory performance (determination of
method detection limits) prior to samples being analyzed
by this method.
9.2.2	Linear 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.
9.2.3	Quality control sample (QCS) - When beginning
the use of this method, on a quarterly basis or as re-
quired to meet data-quality needs, verify the calibration
standards and acceptable instrument performance with
the preparation and analyses of a QCS (Section 7.7). If
the determined concentrations are not within ± 10% of
the stated values, performance of the determinative step
of the method is unacceptable. The source of the prob-
lem must be identified and corrected before either
proceeding with the initial determination of method
detection limits or continuing with ongoing analyses.
9.2.4	Method detection limit (MDL) - MDLs must be
established for all analytes, using reagent water (blank)
fortified at a concentration of two to three times the
estimated instrument detection limit.9 To determine MDL
values, take seven replicate aliquots of the fortified
reagent water and process through the entire analytical
method. Perform all calculations defined in the method
and report the concentration values in the appropriate
units. Calculate the MDL as follows:
MDL = (t) x (S)
where: t = Student's t value for a 99% confidence level
and a standard deviation estimate with n-1
degrees of freedom [t = 3.14 for seven
replicates].
S = standard deviation of the replicate analyses.
Note: If the relative standard deviation (RSD) from the
analyses of the seven aliquots is <15%, the
concentration used to determine the analyte
MDL may have been inappropriately high for the
determination. If so, this could result in the
calculation of an unrealistically low MDL. If
additional confirmation of the MDL is desired,
reanalyze the seven replicate aliquots on two
more nonconsecutive days and again calculate
the MDL values for each day. An average of the
three MDL values for each analyte may provide
for a more appropriate MDL estimate. Concur-
rently, determination of MDL in reagent water
represents a best case situation and does not
reflect possible matrix effects of real world
samples. However, successful analyses of LFMs
(Section 9.4) can give confidence to the MDL
value determined in reagent water. Typical
single laboratory MDL values using this method
are given in Table 1.
MDLs should be determined every six months, when a
new operator begins work or whenever there is a signifi-
cant change in the background or instrument response.
9.3 Assessing Laboratory Performance (Manda-
tory)
9.3.1	Laboratory reagent blank (LRB) — The laboratory
must analyze at least one LRB (Section 7.5.2) with each
batch of 20 or fewer samples. LRB data are used to
assess contamination from the laboratory environment.
LRB values that exceed the MDL indicate laboratory or
reagent contamination should be suspected. Any deter-
mined source of contamination must be corrected and
the samples reanalyzed for the affected analytes after
acceptable LRB values have been obtained.
9.3.2	Laboratory fortified blank (LFB) — The laboratory
must analyze at least one LFB (Section 7.5.3) with each
batch of samples. Calculate accuracy as percent recov-
ery (Section 9.4.3). If the recovery of any analyte falls
outside the required control limits of 85-115%, that
analyte is judged out of control, and the source of the
problem should be identified and resolved before contin-
uing analyses.
9.3.3	The laboratory must use LFB analyses data to
assess laboratory performance against the required con-
trol limits of 85-115% (Section 9.3.2). When sufficient
internal performance data become available (usually a
minimum of 20-30 analyses), optional control limits can
be developed from the percent mean recovery (x) and
the standard deviation (S) of the mean recovery. These
data can be used to establish the upper and lower control
limits as follows:
Upper Control Limit = x + 3S
Lower Control Limit = x - 3S
The optional control limits must be equal to or better than
the required control limits of 85-115%. After each five to
ten new recovery measurements, new control limits can
be calculated using only the most recent 20-30 data
points. Also, the standard deviation (S) data should be
used to established an ongoing precision statement for
the level of concentrations included in the LFB. These
data must be kept on file and be available for review.
9.3.4	Instrument performance check (IPC) solution —
For all determinations the laboratory must analyze the
IPC solution (Section 7.8) and a calibration blank imme-
diately following daily calibration, after every tenth
sample (or more frequently, if required) and at the end of
the sample run. Analysis of the IPC solution and calibra-
tion blank immediately following calibration must verify
that the instrument is within ±10% of calibration. Subse-
Revision 1.6 September 1997
200.10-8

-------
quent analyses of the IPC solution must verify the
calibration within ±15%. If the calibration cannot be
verified within the specified limits, reanalyze the IPC
solution. If the second analysis of the IPC solution
confirms calibration to be outside the limits, sample
analysis must be discontinued, the cause determined
and/or in the case of drift the instrument recalibrated. All
samples following the last acceptable IPC solution must
be reanalyzed. The analysis data of the calibration blank
and IPC solution must be kept on file with the sample
analyses data.
9.3.5 The overall sensitivity and precision of this
method are strongly influenced by a laboratory's ability to
control the method blank. Therefore, it is recommended
that the calibration blank response be recorded for each
set of samples. This record will aid the laboratory in
assessing both its long- and short-term ability to control
the method blank.
9.4 Assessing Analyte Recovery and Data
Quality
9.4.4 If the recovery of any analyte falls outside the
designated LFM recovery range and the laboratory per-
formance for that analyte is shown to be in control
(Section 9.3), the recovery problem encountered with the
LFM is judged to be either matrix or solution related, not
system related.
9.4.5 If analysis of LFM sample(s) and the test rou-
tines above indicate an operative interference and the
LFMs are typical of the other samples in the batch, those
samples that are similar must be analyzed in the same
manner as the LFMs. Also, the data user must be
informed when a matrix interference is so severe that it
prevents the successful analysis of the analyte or when
the heterogeneous nature of the sample precludes the
use of duplicate analyses.
9.4.6 Where reference materials are available, they
should be analyzed to provide additional performance
data. The analysis of reference samples is a valuable
tool for demonstrating the ability to perform the method
acceptably.
9.4.1 Sample homogeneity and the chemical nature of
the sample matrix can affect analyte recovery and the
quality of the data. Taking separate aliquots from the
sample for replicate and fortified analyses can in some
cases assess these effects. Unless otherwise specified
by the data user, laboratory or program, the following
laboratory fortified matrix (LFM) procedure (Section
9.4.2) is required.
9.4.2 The laboratory must add a known amount of
each analyte to a minimum of 10% of the routine sam-
ples. In each case the LFM aliquot must be a duplicate
of the aliquot used for sample analysis and for total
recoverable determinations added prior to sample
preparation. For water samples, the added analyte
concentration must be the same as that used in the
laboratory fortified blank (Section 9.3.2).
9.4.3 Calculate the percent recovery for each analyte,
corrected for concentrations measured in the unfortified
sample, and compare these values to the designated
LFM recovery range of 75-125%. Recovery calculations
are not required if the concentration added is less than
25% of the unfortified sample concentration. Percent
recovery may be calculated in units appropriate to the
matrix, using the following equation:
R
-------
10.4.1 After the calibration has been established, it
must be initially verified for all analytes by analyzing the
IPC (Section 7.8). If the initial calibration verification
exceeds ±10% of the established IPC value, the analysis
should be terminated, the source of the problem identi-
fied and corrected, the instrument recalibrated, and the
new calibration verified before continuing analyses.
10.4.2 To verify that the instrument is properly calibrated
on a continuing basis, analyze the calibration blank
(Section 7.5.1) and IPC (Section 7.8) after every 10
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 10
samples reanalyzed. The instrument responses from the
calibration check may be used for recalibration purposes.
10.5 Internal Standardization - Internal standardiza-
tion must be used in all analyses to correct for instrument
drift and physical interferences. For full mass range
scans, a minimum of three internal standards must be
used. Internal standards must be present in all samples,
standards and blanks at identical levels. This may be
achieved by directly adding an aliquot of the internal
standards to the CAL standard, blank or sample solution
(Method A), or alternatively by mixing with the solution
prior to nebulization using a second channel of the
peristaltic pump and a mixing coil (Method B). The
concentration of the internal standard should be suffi-
ciently high that good precision is obtained in the mea-
surement 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. Internal
standards should be added to blanks, samples and
standards in a like manner, so that dilution effects result-
ing from the addition may be disregarded.
Note: Bismuth should not be used as an internal
standard using the direct addition method (Me-
thod A, Section 10.5) because it is not efficiently
concentrated on the iminodiacetate column.
11.0 Procedure
11.1 Sample Preparation - Total Recoverable
Elements
11.1.1 Add 2-mL(1+1) nitric acid to the beaker contain-
ing 100-mL of sample. Place the beaker on the hot plate
for solution evaporation. The hot plate should be located
in a fume hood and previously adjusted to provide evapo-
ration at a temperature of approximately but no higher
than 85°C. (See the following note.) The beaker should
be covered with an elevated watch glass or other neces-
sary steps should be taken to prevent sample contamina-
tion from the fume hood environment.
Note: For proper heating, adjust the temperature
control of the hot plate such that an uncovered
Griffin beaker containing 50 mL of water placed
in the center of the hot plate can be maintained
at a temperature approximately but no higher
than 85°C. (Once the beaker is covered with a
watch glass the temperature of the water will rise
to approximately 95°C.)
11.1.2 Reduce the volume of the sample aliquot to
about 20-mL by gentle heating at 85°C. Do Not Boil.
This step takes about 2 h for a 100-mL aliquot with the
rate of evaporation rapidly increasing as the sample
volume approaches 20 mL. (A spare beaker containing
20-mL of water can be used as a gauge.)
11.1.3 Cover the lip of the beaker with a watch glass to
reduce additional evaporation and gently reflux the
sample for 30 min. (Slight boiling may occur, but vigor-
ous boiling must be avoided.)
11.1.4 Allow the beaker to cool. Quantitatively transfer
the sample solution to a 100-mL volumetric flask, dilute
to volume with reagent water, stopper and mix.
11.1.5 Allow any undissolved material to settle over-
night, or centrifuge a portion of the prepared sample until
clear. (If after centrifuging or standing overnight, the
sample contains suspended solids, a portion of the
sample may be filtered prior to analysis. However, care
should be exercised to avoid potential contamination
from filtration.) The sample is now ready for analysis.
Because the effects of various matrices on the stability of
diluted samples cannot be characterized, all analyses
should be performed as soon as possible after the
completed preparation.
11.2 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
all the eluent/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 se-
quence three times.
11.2.2 Repeat the sequence described in Section
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.
Revision 1.6 September 1997
200.10-10
-------
11.3 Initiate ICP-MS instrument operating configura-
tion. Tune the instrument for the analytes of interest
(Section 10).
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 config-
ured in a rapid scan/peak hopping mode. The instrument
is now ready to be calibrated.
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.
11.6 Switch on the buffer pump (P2), and pump 2M
ammonium acetate at a flow rate of 1.0 mL/min.
11.7 Preconcentration of the sample may be achieved
by running through an eluent pump program (P1) se-
quence 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 ammo-
nium 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 Section 11.7
for each sample to be analyzed. At the end of the analyti-
cal 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 with 1% HN03 (v/v) and reanalyzed.
12.0 Data Analysis and 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 |jg/L.
Do not report element concentrations below the deter-
mined MDL.
12.2 For data values less than 10, two significant
figures should be used for reporting element concentra-
tions. For data values greater than or equal to 10, three
significant figures should be used.
12.3 Reported values should be calibration blank sub-
tracted. 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 by the application of internal standardization. Correc-
tions 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.
13.0 Method Performance
13.1 Experimental conditions used for single labora-
tory 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 Section 11.1.1. For each
matrix, three replicates were analyzed and the average
of the replicates was used to determine the sample
concentration for each analyte. Two further sets of three
replicates were fortified at different concentration levels,
one set at 0.5 /ig/L, the other at 10 |jg/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.
14.0 Pollution Prevention
14.1 Pollution prevention encompasses any technique
that reduces or eliminates the quantity or toxicity of waste
at the point of generation. Numerous opportunities for
pollution prevention exist in laboratory operation. The
EPA has established a preferred hierarchy of environ-
mental management techniques that place pollution pre-
200.10-11
Revision 1.6 September 1997
-------
vention as the management option of first choice. When-
ever feasible, laboratory personnel should use pollution
prevention techniques to address their waste generation
(e.g., Section 7.8). When wastes cannot be feasibly
reduced at the source, the Agency recommends recy-
cling as the next best option.
14.2 For information about pollution prevention that
may be applicable to laboratories and research institu-
tions, consult Less is Better: Laboratory Chemical Man-
agement for Waste Reduction, available from the Ameri-
can Chemical Society's Department of Government Re-
lations and Science Policy, 1155 16th Street N.W.,
Washington, D.C. 20036, (202)872-4477.
15.0 Waste Management
15.1 The Environmental Protection Agency requires
that laboratory waste management practices be con-
ducted consistent with all applicable rules and regula-
tions. The Agency urges laboratories to protect the air,
water, and land by minimizing and controlling all releases
from hoods and bench operations, complying with the
letter and spirit of any sewer discharge permits and
regulations, and by complying with all solid and hazard-
ous waste regulations, particularly the hazardous waste
identification rules and land disposal restrictions. For
further information on waste management, consult The
Waste Management Manual for Laboratory Personnel,
available from the American Chemical Society at the
address listed in Section 14.2.
16.0 References
1. Siraraks, A., H.M. Kingston, and J.M. Riviello,
AnalChem. 62,1185 (1990).
2. Heithmar, E.M., T.A. Hinners, J.T. Rowan, and
J.M. Riviello, Anal Chem., 62, 857 (1990).
3. Gray A.L. and A.R. Date, Analyst, 108, 1033
(1983).
4. Houk, R.S., et al. Anal. Chem., 52, 2283 (1980).
5. Houk, R.S., Anal.Chem., 58, 97A (1986).
6. J. J. Thompson and R.S. Houk, Appl. Spec., 41,
801 (1987).
7. OSHA Safety and Health Standards, General
Industry, (29 CFR 1910), Occupational Safety
and Health Administration, OSHA 2206, (Re-
vised, January 1976).
8. Safety in Academic Chemistry Laboratories,
American Chemical Society Publication, Commit-
tee on Chemical Safety, 3rd Edition, 1979.
9. Code of Federal Regulations 40, Ch. 1, Pt. 136
Appendix B.
Revision 1.6 September 1997
200.10-12
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17.0 Tables, Diagrams, Flowcharts, and Validation Data
Table 1. Total Recoverable Method Detection Limits for Reagent Water
Recommended MDL1
Element Analytical Mass //g/L
Cadmium 111 0.041
Cobalt 59 0.021
Copper 63 0.023
Lead 206,207,208 0.074
Nickel 60 0.081
Uranium 238 0.031
Vanadium 51 0.014
1 Determined using 10-mL sample loop.
Table 2. Eluent Pump Programming Sequence for Preconcentration of Trace Elements
Time
(min)
Flow
(mL/min)
Eluent
Valve
A.B
Valve
C
0.0
4.0
1M ammonium acetate
ON
ON
4.5
4.0
1.25M nitric acid
ON
ON
5.1
1.0
1.25M nitric acid
OFF
ON
5.5
1.0
1.25M nitric acid
OFF
OFF
7.5
4.0
1.25M nitric acid
OFF
ON
8.0
4.0
1M ammonium acetate
OFF
ON
10.0
4.0
1.25M nitric acid
OFF
ON
11.0
4.0
1M ammonium acetate
OFF
ON
12.5
0.0

OFF
ON
Table 3. Recommended Analytical Isotopes and Elemental Equations for Data Calculations
Element Isotope Elemental Eguation Note
Cd
106, 108, 111, 114
(1.000)(111C)-(1.073)[(1C8C)-(0.712)(1C6C)]
(1)
Co
59
(1,000)(59C)

Cu
63, 65
(1,000)(63C)

Pb
206, 207, 208
(1,000)(2C6C)+(1,000)(2C7C)+(1,000)(2C8C)
(2)
Ni
60
(1,000)(6°C)

U
238
(1,000)(238C)

V
51
(1.000)(51C)

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.
(2) - allowance for isotopic variability of lead isotopes.
NOTE: As a minimum, all isotopes listed should be monitored. Isotopes recommended for analytical determination are italized.
200.10-13
Revision 1.6 September 1997
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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
VG PlasmaQuad Type I
1.35 kW
13.5 L/min
0.6 L/min
0.78 L/min
Internal standards
Sc, Y, In, Tb
Data Acquisition
Detector mode
Mass range
Dwell time
Number of MCA channels
Number of scan sweeps
Pulse counting
45-240 amu
160 //s
2048
250
Table 5. Precision and Recovery Data for Estuarine Water (SLEW-1)

Sample
Spike
Average

Spike
Average

Certificate
Cone.
Addition
Recovery
RSD
Addition
Recovery
RSD
Analyte
(mB/L)
(mB/L)
(MP/L)
(%)
(%)
(mB/L)
(%)
(%)
Cd
0.018
<0.041
0.5
94.8
9.8
10
99.6
1.1
Co
0.046
0.078
0.5
102.8
4.0
10
96.6
1.4
Cu
1.76
1.6
0.5
106.0
2.7
10
96.0
4.8
Pb
0.028
<0.074
0.5
100.2
4.0
10
106.9
5.8
Ni
0.743
0.83
0.5
100.0
1.5
10
102.0
2.1
U
-
1.1
0.5
96.7
7.4
10
98.1
3.6
V
—
1.4
0.5
100.0
3.2
10
97.0
4.5
- No certificate value
Table 6. Precision and Recovery Data for Seawater (NASS-2)

Sample
Spike
Average

Spike
Average

Certificate
Cone.
Addition
Recovery
RSD
Addition
Recovery
RSD
Analyte
(Mfl/L)
(mB/L)
(Mfl/L)
(%)
(%)
(Mfl/L)
(%)
(%)
Cd
0.029
<0.041
0.5
101.8
1.0
10
96.4
3.7
Co
0.004
<0.021
0.5
98.9
3.0
10
99.2
1.7
Cu
0.109
0.12
0.5
95.8
2.3
10
93.1
0.9
Pb
0.039
<0.074
0.5
100.6
8.5
10
92.1
2.6
Ni
0.257
0.23
0.5
102.2
2.3
10
98.2
1.2
U
3.00
3.0
0.5
94.0
0.7
10
98.4
1.7
V
—
1.7
0.5
104.0
3.4
10
109.2
3.7
-No certificate value
Revision 1.6 September 1997
200.10-14
-------
\Na ste
\Naste
\Na ste
K5

10 mL
Loop

Chelating
Column
I
I
I
Buffer
Pump
P2
2M NhjjOAc
P/STALTIC
Pump
Sample
P4
Eluent
Pump
P1
1M
Nh^OAc 1.25 M Nitric Add
Carrier
Pump
P3
1%NtricAcid
ICP-MS
Mixing Tee
Figure 1. Configuration of Preconcentration System.
Off
On
200.10-15
Revision 1.6 September 1997
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