ASTM D6800-02

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D6800–02
Standard Practice for
Preparation of Water Samples Using Reductive Precipitation
Preconcentration Technique for ICP-MS Analysis of Trace
Metals
This standard is issued under the fixed designation D 6800; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 5673 Test Method for Elements in Water by Inductively
Coupled Plasma Mass Spectrometry
1.1 Toxic elements may be present in ambient waters and
D 5810 Guide for Spiking into Aqueous Samples
may enter the food chain via uptake by plants and animals; the
D 5847 Practice for Writing Quality Control Specifications
actual concentrations of toxic metals are usually sub-ng/mL.
for Standard Test Methods for Water Analysis
The U.S. EPAhas published its Water Quality Standards in the
2.2 Other Documents:
U.S. Federal Register 40 CFR 131.36, Minimum requirements
U.S. Federal Register 40 CFR 131.36, Minimum Require-
for water quality standards submission, Ch. I (7-1-00 Edition),
ments for Water Quality Standards Submission, Ch. I
see Annex, Table A1.1. The U.S. EPA has also developed
(7-1-00 Edition)
Method 1640 to meet these requirements, see Annex, Table
U.S.EPAMethod1640, DeterminationofTraceElementsin
A1.2.
Water by Preconcentration and Inductively Coupled
1.2 Inductively Coupled Plasma Mass Spectroscopy (ICP-
Plasma-Mass Spectrometry (1997)
MS) is a technique with sufficient sensitivity to routinely
U.S. EPAMethod 1669, SamplingAmbient Water for Trace
measure toxic elements in ambient waters, both fresh and
Metals at EPA Water Quality Criteria Levels
saline (Test Method D 5673). However saline and hard water
matrices pose analytical challenges for direct multielement
3. Terminology
analysis by ICP-MS at the required sub-ng/mL levels.
3.1 Definitions—For definitions of terms used in this test
1.3 This standard practice describes a method used to
method refer to Terminology D 1129.
prepare water samples for subsequent multielement analysis
3.2 Definitions of Terms Specific to This Standard:
using ICP-MS.The practice is applicable to seawater and fresh
3.2.1 dissolved—the concentration of elements determined
water matrices, which may be filtered or digested. Samples
on a filtered fraction of a sample. Samples are filtered through
preparedbythismethodhavebeenanalyzedbyICP-MSforthe
a 0.45 µm membrane filter before acid preservation.
elements listed in Annex, Table A1.3).
3.2.2 intermediate stock standard solution—a diluted solu-
1.4 This standard does not purport to address all of the
tion prepared from one or more of the stock standard solutions.
safety concerns, if any, associated with its use. It is the
3.2.3 laboratory control sample (LCS)—an aliquot of solu-
responsibility of the user of this standard to establish appro-
tion with known concentrations of method analytes. It should
priate safety and health practices and determine the applica-
be obtained from a reputable source or prepared at the
bility of regulatory limitations prior to use.
laboratory from a separate source from the calibration stan-
2. Referenced Documents dards.TheLCSisanalyzedusingthesamesamplepreparation,
analyticalmethodandQA/QCprocedureusedfortestsamples.
2.1 ASTM Standards:
Its purpose is to determine whether method performance is
D 1129 Terminology Relating to Water
within accepted control limits.
D 1193 Specification for Reagent Water
3.2.4 laboratory duplicate (LD)—a second aliquot of a
sample should be analyzed using the same sample preparation,
This practice is under the jurisdiction ofASTM Committee D19 on Water and
analyticalmethodandQA/QCprocedureusedfortestsamples.
is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in
Water.
Current edition approved May 10, 2002. Published July 2002.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available from DODSSP, Bldg. 4, Section D, 700 RobbinsAve., Philadelphia,
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM PA 19111–5098.
Standards volume information, refer to the standard’s Document Summary page on Available from U.S. EPA, Ariel Rios Bldg., 1200 Pennsylvania Ave., NW,
the ASTM website. Washington, DC 20460.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6800–02
Its purpose is to determine whether method performance is preconcentrated by a factor of 10 by reductive precipitation
within accepted control limits. using sodium borohydride as a reducing agent.
4.2 Iron(Fe)andpalladium(Pd)areaddedtothesamplesto
3.2.5 matrix spike (MS)—a second aliquot of a sample to
which known concentrations of target analyte(s) are added in aid co-precipitation of metal borides and to enhance the
precipitation of metals in their elemental form.
the laboratory and should be analyzed using the same sample
preparation and analytical method used for test samples. Its 4.3 For total metals, the whole sample is acidified at the
time of collection with ultrapure nitric acid at an equivalent
purpose is to determine whether the sample matrix contributes
bias to the analytical results. The background concentration of concentration of 0.20 % to a pH < 2.
4.4 For dissolved metals, the sample is filtered through a
the matrix must be determined in a separate aliquot and the
measured values in the MS corrected for the concentrations 0.45 µm filter at the time of collection then acidified with
ultrapurenitricacidatanequivalentconcentrationof0.20 %to
found. Recommended spike levels are listed in Annex, Table
A1.3. apH<2.
3.2.6 method blank (MB)—suitable aliquots of reagent wa-
NOTE 1—It is important to minimize the amount of nitric acid used to
ter are analyzed using the same sample preparation technique,
preserve the samples. A pH adjustment to a pH between 8 and 10 using
analyticalmethodandQA/QCprocedureusedfortestsamples.
ammonium hydroxide is performed during the co-precipitation reaction
and it is important to minimize the amount of ammonium hydroxide
The MB is used to determine if method analytes or other
required for this adjustment to reduce potential contamination of the
interferences are present in the laboratory environment, the
samples.
reagents or apparatus.
3.2.7 method detection limit (MDL)—determined as de-
4.5 The precipitate is collected by filtration through a 0.4
scribed in the U.S. Federal Register (see 40 CFR Part 136,
mm filter and the salt matrix is eliminated with the filtrate.The
Appendix B).
filter and precipitate are digested with nitric acid and hydrogen
3.2.8 reagent water—standard laboratory water purified to peroxide for analysis by ICP-MS.
meet Specification D 1193 Type I or better.
3.2.9 reporting detection limit (RDL)—the lowest concen-
5. Significance and Use
trationatwhichananalytecanbereliablyquantified.TheRDL
5.1 Ambient marine waters generally contain very low
represents the minimum concentration at which method per-
concentrations of toxic metals that require sensitive analytical
formance becomes quantitative and is not subject to the degree
methods, such as ICP-MS, to detect and measure the metal’s
of variation observed at concentrations between the MDL and
concentrations.
the RDL.
5.2 Due to the high dissolved salt concentrations present in
3.2.10 spiked blank (SB)—an aliquot of reagent water to
seawater, sample pretreatment is required to remove signal
which known concentrations of analyte(s) is added in the
suppression and significant polyatomic interferences due to the
laboratory, using the same solution as used to prepare the
matrix both of which compromise detection limits.
matrix spike. The spike blank is analyzed using the same
sample preparation, analytical method and QA/QC procedure
6. Interferences
used for test samples. The purpose of the spike blank is to
6.1 Contamination—Concentrations of trace metals in am-
determine whether method performance is within acceptable
bient marine waters may be very low and it is imperative that
limits.Thespikeblankisalsousefulfortroubleshootingmatrix
extreme care be taken to avoid contamination when collecting,
spike results that are outside the acceptance limits, by allowing
preparing and analyzing ambient water samples. U.S. EPA
the analyst to differentiate between spike solution and spiking
Method 1669 details appropriate clean sampling protocols.
technique problems and matrix interferences. Recommended
6.2 Isobaric polyatomic ion interferences are caused by ions
spike levels are listed in Annex, Table A1.3.
consistingofmorethanoneatomwhichhavethesamenominal
3.2.11 stock standard solution—a concentrated solution
mass-to-charge ratio as the isotope of interest, and which may
containing one or more analytes, obtained as a certified
notberesolvedbythemassspectrometerinuse.Theseionsare
solution form a reputable source.
commonly formed in the plasma or interface system from
3.2.12 surrogate spikes—lanthanum and terbium are added
support gases or sample components. Most of the common
ataconcentrationof5ng/mLintheinitial100-mLsample.The
interferences have been identified, and are listed in Test
surrogate spikes are then preconcentrated to approximately 50
Method D 5673. Such interferences must be recognized, and
ng/mL in the final 10-mL sample not correcting for the final
when they cannot be avoided by the selection of alternative
preconcentration. The surrogate spikes are used to determine
analytical isotopes, appropriate corrections must be made to
potential method problems such as improper pH adjustment or
the data. Equations for the correction of data should be
faulty filters used when collecting the precipitate.
established at the time of the analytical run sequence, as the
3.2.13 total recoverable—the concentration of analyte de-
polyatomic ion interferences will be highly dependent on the
termined on a whole, unfiltered water or solid sample follow-
sample matrix and chosen instrument operating parameters.
ing vigorous digestion as described in US EPA Method 1640.
Majorinterferingionsfromseawatermatrixesareeliminatedin
this practice by the selective precipitation of metals.
4. Summary of Practice
6.3 Palladium reagent in the analyzed samples interferes
107 109
4.1 In this practice, trace elements are separated from with both silver masses Ag and Ag due to the formation
+
seawater matrix elements (in particular Na, Ca, and Mg) and of the PdH ion.
D6800–02
7. Hazards cleanliness is monitored by the method blanks. Refer to U.S.
EPA Method 1669 for guidance.
7.1 The toxicity or carcinogenicity of reagents used in this
9.2 Hot Block, capable of 70°C.
method has not been fully established. Each chemical should
9.3 Vacuum Filter Holder, with a viton o-ring and a silicone
be regarded as a potential health hazard and exposure to these
stopper.
compounds should be as low as reasonably achievable. A
9.4 25 mm Polysulphone Filter Funnel, 200 mL capacity.
referencefileofmaterialdatahandlingsheets(MSDS)foreach
9.5 PVC Vacuum Manifold.
chemical used in this procedure should be available to all
9.6 Filter Dome, 2000 mL capacity.
personnel involved in the chemical analysis.
9.7 Oil-Free Vacuum Pump.
8. Sample Collection, Containers, Preservation, and
9.8 Analytical Balance.
Storage
9.9 Metal-Free Pipettes, capable of delivering varying
8.1 Allsamplesmustbecollectedusingasamplingplanthat amounts from microlitres (µL) to millilitres (mL).
addresses the considerations discussed in U.S. EPA Method 9.10 500 mL Fluoropolymer Separatory Funnel.
1669. Contamination control is critical at all steps of sample 9.11 125 mL High-Density Polyethylene (HDPE) Bottles.
handling due to the low measurement limit goals of this
9.12 125 mL and 250 mL Wide-Mouth Fluoropolymer
method.
Bottles.
8.2 Water samples must be acidified with an equivalent
9.13 Fluoropolymer Tweezers.
concentration of 0.2 % ultrapure nitric acid (that is, 1 mL
9.14 Automated Pipette, for acid dispensing. Capable of
HNO to 500 mL sample). Samples are kept at room tempera-
3 accurately delivering 0.25 to 5.0 mL.
tureinplasticbins.Usetheminimumamountofacidnecessary
9.15 Polypropylene Specimen Cups and Polypropylene
to reduce the sample pH < 2. Excess acid will complicate the
Lids.
pH adjustment during the reductive precipitation reaction.
9.16 250 mL Polypropylene Graduated Cylinders.
8.3 Use only acid washed sample containers prepared as
9.17 100 mL Polymethylpentene (PMP) Graduated Cylin-
described in US EPAMethod 1669. High-density polyethylene
ders.
(HDPE) is preferred.
9.18 Laminar Flow Polypropylene Fume Hood.
8.4 Sample Preservation:
8.4.1 Total Recoverable Metals—For determination of total
10. Standards, Reagents, and Consumables
recoverable elements in aqueous samples, preserve the whole
10.1 Consumables:
sample by adding ultra pure nitric acid to pH < 2 (normally 1
10.1.1 125 mL environmental sampling bottles, high-
mL per 500 mL of sample) at the time of collection or upon
density polyethylene (HDPE), wide mouth.
receipt with an equivalent concentration of 0.2 % ultrapure
10.1.2 15 mL calibrated disposable polypropylene centri-
nitric acid (that is, 1 mL HNO to 500 mL sample).
fuge tubes.
NOTE 2—Samples that cannot be acid preserved at the time of collec-
10.1.3 20 mm polypropylene caps.
tion because of sampling limitations or transport restrictions, should be
10.1.4 50 mL or 100 mL volumetric flask, polypropylene.
acidified with ultra pure acid to pH < 2 upon receipt in the laboratory.
10.1.5 pH test papers, dual tint, pH range 7.0 to 10.0,
These samples must be then held for 16 h prior to sample preparation.
accurate to 0.1.
8.4.2 Dissolved Metals—For the determination of dissolved
10.1.6 Polycarbonate Filters:
elements,thesamplesarefilteredthrougha0.45µmmembrane
10.1.6.1 25 mm diameter, 0.4 µm pore size.
filter or equivalent. Acidify the filtrate with ultra pure nitric
10.1.6.2 47 mm diameter, 0.4 µm pore size.
acid to pH < 2 immediately following filtration.
10.1.6.3 47 mm diameter, 0.2 µm pore size.
9. Apparatus and Equipment
10.1.7 Metal-Free Laboratory Gloves.
10.2 Purity of Reagents—All reagents may contain impuri-
9.1 Laboratory Equipment—For the determination of trace
ties that may affect the integrity of the analytical results. Due
levels of elements, contamination and loss are of primary
to the high sensitivity of ICP-MS, high-purity reagents, water,
consideration.Potentialcontaminationsourcesincludeimprop-
and acids must be used whenever possible. All acids used for
erly cleaned laboratory apparatus and general contamination
this method must be of ul
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