ASTM D6800-02(2007)e1

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D6800–02 (Reapproved 2007)
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 D6800; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope D5673 Test Method for Elements in Water by Inductively
Coupled Plasma—Mass Spectrometry
1.1 Toxic elements may be present in ambient waters and
D5810 Guide for Spiking into Aqueous Samples
may enter the food chain via uptake by plants and animals; the
D5847 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 D5673). 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 D1129.
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,
2 analyticalmethodandQA/QCprocedureusedfortestsamples.
2.1 ASTM Standards:
Its purpose is to determine whether method performance is
D1129 Terminology Relating to Water
within accepted control limits.
D1193 Specification for Reagent Water
3.2.4 laboratory duplicate (LD)—a second aliquot of a
sample should be analyzed using the same sample preparation,
1 analyticalmethodandQA/QCprocedureusedfortestsamples.
This practice is under the jurisdiction ofASTM Committee D19 on Water and
Its purpose is to determine whether method performance is
is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in
Water.
within accepted control limits.
Current edition approved Aug. 1, 2007. Published September 2007. Originally
approved in 2002. Last previous edition approved in 2002 as D6800 – 02. DOI:
10.1520/D6800-02R07E01. Available from DODSSP, Bldg. 4, Section D, 700 RobbinsAve., Philadelphia,
For referenced ASTM standards, visit the ASTM website, www.astm.org, or PA 19111–5098.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available from United States Environmental Protection Agency (EPA), Ariel
Standards volume information, refer to the standard’s Document Summary page on Rios Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460, http://
the ASTM website. www.epa.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D6800–02 (2007)
3.2.5 matrix spike (MS)—a second aliquot of a sample to 4.2 Iron(Fe)andpalladium(Pd)areaddedtothesamplesto
which known concentrations of target analyte(s) are added in aid co-precipitation of metal borides and to enhance the
the laboratory and should be analyzed using the same sample
precipitation of metals in their elemental form.
preparation and analytical method used for test samples. Its
4.3 For total metals, the whole sample is acidified at the
purpose is to determine whether the sample matrix contributes
time of collection with ultrapure nitric acid at an equivalent
bias to the analytical results. The background concentration of
concentration of 0.20 % to a pH < 2.
the matrix must be determined in a separate aliquot and the
4.4 For dissolved metals, the sample is filtered through a
measured values in the MS corrected for the concentrations
0.45 µm filter at the time of collection then acidified with
found. Recommended spike levels are listed in Annex, Table
ultrapurenitricacidatanequivalentconcentrationof0.20 %to
A1.3.
apH<2.
3.2.6 method blank (MB)—suitable aliquots of reagent wa-
ter are analyzed using the same sample preparation technique,
NOTE 1—It is important to minimize the amount of nitric acid used to
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
The MB is used to determine if method analytes or other
and it is important to minimize the amount of ammonium hydroxide
interferences are present in the laboratory environment, the
required for this adjustment to reduce potential contamination of the
reagents or apparatus.
samples.
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,
Appendix B). mm filter and the salt matrix is eliminated with the filtrate.The
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 D1193 Type I or better.
3.2.9 reporting detection limit (RDL)—the lowest concen-
5. Significance and Use
trationatwhichananalytecanbereliablyquantified.TheRDL
represents the minimum concentration at which method per-
5.1 Ambient marine waters generally contain very low
formance becomes quantitative and is not subject to the degree
concentrations of toxic metals that require sensitive analytical
of variation observed at concentrations between the MDL and
methods, such as ICP-MS, to detect and measure the metal’s
the RDL.
concentrations.
3.2.10 spiked blank (SB)—an aliquot of reagent water to
5.2 Due to the high dissolved salt concentrations present in
which known concentrations of analyte(s) is added in the
seawater, sample pretreatment is required to remove signal
laboratory, using the same solution as used to prepare the
suppression and significant polyatomic interferences due to the
matrix spike. The spike blank is analyzed using the same
matrix both of which compromise detection limits.
sample preparation, analytical method and QA/QC procedure
used for test samples. The purpose of the spike blank is to
6. Interferences
determine whether method performance is within acceptable
limits.Thespikeblankisalsousefulfortroubleshootingmatrix 6.1 Contamination—Concentrations of trace metals in am-
spike results that are outside the acceptance limits, by allowing bient marine waters may be very low and it is imperative that
the analyst to differentiate between spike solution and spiking extreme care be taken to avoid contamination when collecting,
technique problems and matrix interferences. Recommended
preparing and analyzing ambient water samples. U.S. EPA
spike levels are listed in Annex, Table A1.3. Method 1669 details appropriate clean sampling protocols.
3.2.11 stock standard solution—a concentrated solution
6.2 Isobaric polyatomic ion interferences are caused by ions
containing one or more analytes, obtained as a certified
consistingofmorethanoneatomwhichhavethesamenominal
solution form a reputable source.
mass-to-charge ratio as the isotope of interest, and which may
3.2.12 surrogate spikes—lanthanum and terbium are added
notberesolvedbythemassspectrometerinuse.Theseionsare
ataconcentrationof5ng/mLintheinitial100-mLsample.The
commonly formed in the plasma or interface system from
surrogate spikes are then preconcentrated to approximately 50
support gases or sample components. Most of the common
ng/mL in the final 10-mL sample not correcting for the final
interferences have been identified, and are listed in Test
preconcentration. The surrogate spikes are used to determine
Method D5673. Such interferences must be recognized, and
potential method problems such as improper pH adjustment or
when they cannot be avoided by the selection of alternative
faulty filters used when collecting the precipitate.
analytical isotopes, appropriate corrections must be made to
3.2.13 total recoverable—the concentration of analyte de-
the data. Equations for the correction of data should be
termined on a whole, unfiltered water or solid sample follow-
established at the time of the analytical run sequence, as the
ing vigorous digestion as described in US EPA Method 1640.
polyatomic ion interferences will be highly dependent on the
sample matrix and chosen instrument operating parameters.
4. Summary of Practice
Majorinterferingionsfromseawatermatrixesareeliminatedin
this practice by the selective precipitation of metals.
4.1 In this practice, trace elements are separated from
seawater matrix elements (in particular Na, Ca, and Mg) and 6.3 Palladium reagent in the analyzed samples interferes
107 109
preconcentrated by a factor of 10 by reductive precipitation with both silver masses Ag and Ag due to the formation
+
using sodium borohydride as a reducing agent. of the PdH ion.
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D6800–02 (2007)
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,
...