ASTM D1971-02(2006)
(Practice)Standard Practices for Digestion of Water Samples for Determination of Metals by Flame Atomic Absorption, Graphite Furnace Atomic Absorption, Plasma Emission Spectroscopy, or Plasma Mass Spectrometry
Standard Practices for Digestion of Water Samples for Determination of Metals by Flame Atomic Absorption, Graphite Furnace Atomic Absorption, Plasma Emission Spectroscopy, or Plasma Mass Spectrometry
SIGNIFICANCE AND USE
The determination of metals in water often requires the measurement of total (suspended and dissolved) metals as well as soluble (dissolved) metals. In such cases, consistent and dependable digestion procedures must be used so that data derived for the total metals content is reliable.
The practices given are applicable to a wide variety of sample types for the purpose of preparing a sample for metals analyses by atomic absorption spectrophotometry or plasma emission spectroscopy (see Test Methods D 1976, D 3919, D 4691, and D 4190) or plasma-mass spectrometry (See Test Method D 5673) and have been shown to give good recovery in the following matrices: industrial effluents; waste water treatment plant influents, sludges, dewatered sludges, and effluents; river and lake waters; and plant and animal tissues. Elements which have shown good recovery include: copper, nickel, lead, zinc, cadmium, iron, manganese, magnesium, and calcium.
4.2.1 Good recovery for the indicated sample types and metals may not be achieved at all times due to each sample’unique characteristics. Users must always validate the practice for their particular samples.
The analytical results achieved after applying these practices cannot necessarily be deemed as a measure of bioavailable or environmentally available elements.
These three practices may not give the same recovery when applied to the same sample, nor will they necessarily give the same results as achieved using other digestion techniques. An alternate digestion technique is Practice D 4309.
SCOPE
1.1 Most atomic absorption and plasma emission spectroscopy, and plasma-mass spectrometric test methods require that the metals of interest be dissolved in a liquid phase before being introduced into the spectrophotometer. These practices describe digestion or dissolution procedures whereby analyte metals associated with the solid fraction of a sample can be brought into solution for subsequent analysis. The following practices are included: SectionsPractice A-Digestion with Mineral Acids and Elevated Pressure8 through 13Practice B-Digestion with Mineral Acids and Heating at Atmospheric Pressure14 through 19Practice C-In-bottle digestion with Mineral Acids20 through 25
1.2 These practices have been demonstrated to be applicable to a wide variety of sample types and sample matrices, and in many cases, will give complete dissolution of the analyte metals of interest. They are by no means the only digestion procedures available.
1.3 The user of these practices should be cautioned that these practices may not completely dissolve all portions of a sample's solid phase and may not give complete recovery of the desired analyte metals. In these cases, other digestion techniques are available that will effect complete dissolution of a sample. It is the user's responsibility to ensure the validity of these practices for use on their particular sample matrix, for their metals of interest.
1.4 This practice assumes that the criteria established in Guide D 3856 can be met.
1.5 These digestion procedures have been selected for their wide application, low cost, and ease of use.
1.6 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements are given in Section 6.
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Designation:D1971–02 (Reapproved 2006)
Standard Practices for
Digestion of Water Samples for Determination of Metals by
Flame Atomic Absorption, Graphite Furnace Atomic
Absorption, Plasma Emission Spectroscopy, or Plasma
Mass Spectrometry
This standard is issued under the fixed designation D1971; 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 1.7 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 Most atomic absorption and plasma emission spectros-
responsibility of the user of this standard to establish appro-
copy, and plasma-mass spectrometric test methods require that
priate safety and health practices and determine the applica-
the metals of interest be dissolved in a liquid phase before
bility of regulatory limitations prior to use. Specific hazard
being introduced into the spectrophotometer. These practices
statements are given in Section 6.
describe digestion or dissolution procedures whereby analyte
metals associated with the solid fraction of a sample can be
2. Referenced Documents
brought into solution for subsequent analysis. The following
2.1 ASTM Standards:
practices are included:
D511 Test Methods for Calcium and Magnesium In Water
Sections
D857 Test Method for Aluminum in Water
PracticeA—Digestion with MineralAcids and 8 through 13
Elevated Pressure
D858 Test Methods for Manganese in Water
Practice B—Digestion with MineralAcids and 14 through 19
D1068 Test Methods for Iron in Water
Heating atAtmospheric Pressure
D1129 Terminology Relating to Water
Practice C—In-bottle digestion with MineralAcids 20 through 25
D1192 Guide for Equipment for SamplingWater and Steam
1.2 Thesepracticeshavebeendemonstratedtobeapplicable
in Closed Conduits
to a wide variety of sample types and sample matrices, and in
D1193 Specification for Reagent Water
many cases, will give complete dissolution of the analyte
D1687 Test Methods for Chromium in Water
metals of interest. They are by no means the only digestion
D1688 Test Methods for Copper in Water
procedures available.
D1691 Test Methods for Zinc in Water
1.3 The user of these practices should be cautioned that
D1886 Test Methods for Nickel in Water
these practices may not completely dissolve all portions of a
D1976 Test Method for Elements in Water by Inductively-
sample’s solid phase and may not give complete recovery of
Coupled Argon Plasma Atomic Emission Spectroscopy
the desired analyte metals. In these cases, other digestion
D3370 Practices for Sampling Water from Closed Conduits
techniques are available that will effect complete dissolution of
D3372 Test Method for Molybdenum in Water
a sample. It is the user’s responsibility to ensure the validity of
D3557 Test Methods for Cadmium in Water
these practices for use on their particular sample matrix, for
D3558 Test Methods for Cobalt in Water
their metals of interest.
D3559 Test Methods for Lead in Water
1.4 This practice assumes that the criteria established in
D3645 Test Methods for Beryllium in Water
Guide D3856 can be met.
D3856 Guide for Good Laboratory Practices in Laborato-
1.5 These digestion procedures have been selected for their
ries Engaged in Sampling and Analysis of Water
wide application, low cost, and ease of use.
D3866 Test Methods for Silver in Water
1.6 The values stated in SI units are to be regarded as the
D3919 Practice for Measuring Trace Elements in Water by
standard. The values given in parentheses are for information
Graphite Furnace Atomic Absorption Spectrophotometry
only.
1 2
These practices are under the jurisdiction of ASTM Committee D19 on Water For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and are the direct responsibility of Subcommittee D19.05 on Inorganic Constituents contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
in Water. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Dec. 15, 2006. Published February 2007. Originally the ASTM website.
approved in 1991. Last previous edition approved in 2002 as D1971 – 02. DOI: Withdrawn. The last approved version of this historical standard is referenced
10.1520/D1971-02R06. on www.astm.org.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959, United States.
D1971–02 (2006)
D4190 Test Method for Elements in Water by Direct- the following matrices: industrial effluents; waste water treat-
Current Plasma Atomic Emission Spectroscopy ment plant influents, sludges, dewatered sludges, and effluents;
D4191 Test Method for Sodium in Water by Atomic Ab- river and lake waters; and plant and animal tissues. Elements
sorption Spectrophotometry which have shown good recovery include: copper, nickel, lead,
D4192 Test Method for Potassium in Water by Atomic zinc, cadmium, iron, manganese, magnesium, and calcium.
Absorption Spectrophotometry
4.2.1 Good recovery for the indicated sample types and
D4309 Practice for Sample Digestion Using Closed Vessel
metals may not be achieved at all times due to each sample’s
Microwave Heating Technique for the Determination of
unique characteristics. Users must always validate the practice
Total Metals in Water
for their particular samples.
D4691 Practice for Measuring Elements in Water by Flame
4.3 The analytical results achieved after applying these
Atomic Absorption Spectrophotometry
practices cannot necessarily be deemed as a measure of
D5673 Test Method for Elements in Water by Inductively
bioavailable or environmentally available elements.
Coupled Plasma—Mass Spectrometry
4.4 These three practices may not give the same recovery
2.2 U.S. EPA Method:
when applied to the same sample, nor will they necessarily
EPA-600/4-79-020 Methods for Chemical Analysis of Wa-
give the same results as achieved using other digestion
ter and Wastes
techniques.AnalternatedigestiontechniqueisPracticeD4309.
EPA-600/R-94/111 Methods for the Determination of Met-
als in Environmental Samples—Supplement 1
5. Reagents
2.3 U.S. Geological Survey Method:
U.S. Geological Survey Open File Report 96–225: Methods 5.1 Purity of Reagents—Reagent grade chemicals shall be
used throughout. Acids shall have a low-metal content or
ofAnalysis by the U.S. Geological Survey NationalWater
Quality Laboratory—In-Bottle Acid Digestion of Whole should be doubly distilled and checked for purity. Unless
otherwise indicated, it is intended that all reagents shall
Water Samples
Quality Laboratory—In-Bottle Acid Digestion of Whole conform to the Specifications of the Committee on Analytical
Reagents of the American Chemical Society. Other grades
Water Samples
may be used, provided it is first ascertained that the reagent is
3. Terminology
of sufficiently high purity to permit its use without lessening
the accuracy of the determination.
3.1 Definitions: For definitions of terms used in these
practices, refer to Terminology D1129.
5.2 Purity of Water—Unless otherwise indicated, references
3.2 Definitions of Terms Specific to This Standard:
towatershallbeunderstoodtomeanreagentwaterconforming
3.2.1 digestion—treating a sample with the use of heat or
to Specification D1193, Type I. Other reagent water types may
elevated pressures, or both, usually in the presence of chemical
be used, provided it is first ascertained that the water is of
additives, to bring analytes of interest into solution or to
sufficiently high purity to permit its use without lessening the
remove interfering matrix components, or both.
bias and precision of the determination.
3.2.2 total recoverable—the amount of a metal analyte
measurable by atomic absorption spectrophotometry, plasma
6. Hazards
emission spectroscopy or plasma mass spectrometry after
6.1 These practices involve the heating of solutions of
applying the digestion procedure in either Practice A, Practice
mineralacids.Appropriateprecautionsshallbetakentoprotect
B, or Practice C. The choice of Practice A, B, or C shall be
the analyst from these acids and heated containers. Heated
noted in reporting resultant data.
samples and acids may splatter or boil unexpectedly.
4. Significance and Use
7. Sampling
4.1 The determination of metals in water often requires the
measurement of total (suspended and dissolved) metals as well 7.1 As with all chemical assay procedures, the user of this
as soluble (dissolved) metals. In such cases, consistent and
practiceshallensurethatallsamplealiquotusedareadequately
dependable digestion procedures must be used so that data representative of the environmental situation being monitored.
derived for the total metals content is reliable.
7.2 Appropriate sampling and subsampling techniques for
4.2 The practices given are applicable to a wide variety of
particular environmental samples can be found in other refer-
sample types for the purpose of preparing a sample for metals
ences.
analyses by atomic absorption spectrophotometry or plasma
7.3 Collect the sample in accordance with Specification
emission spectroscopy (see Test Methods D1976, D3919,
D1192 and Practices D3370.
D4691, and D4190) or plasma-mass spectrometry (See Test
Method D5673) and have been shown to give good recovery in
Reagent Chemicals, American Chemical Society Specifications , American
Revised March 1983. Published by the United States Environmental Protection Chemical Society, Washington, DC. For suggestions on the testing of reagents not
Agency. Available from Superintendent of Documents, U.S. Government Printing listed by the American Chemical Society, see Analar Standards for Laboratory
Office, Washington, DC 20402. Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
Available from USGS National Center, 12201 Sunrise Valley Dr., Reston, VA and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
20192, USA. MD.
D1971–02 (2006)
PRACTICE A—DIGESTION WITH MINERAL 11.3 Chemical Interferences—The complete dissolution of
ACIDS AND a metal of interest may not occur due to the digestion
ELEVATED PRESSURE conditions being insufficiently rigorous for that particular
metal. In other instances, the chemical makeup of the sample
8. Scope
may render the digestion acids ineffective.
8.1 This practice presents a digestion technique that has
broad application and can be performed inexpensively with
12. Reagents
minimal labor, equipment, and space. In addition, this practice
12.1 Hydrochloric Acid (sp gr 1.19)—Concentrated hydro-
allows for many samples to be processed quickly and simul-
chloric acid (HCl).
taneously under the same conditions.
12.2 Nitric Acid (sp gr 1.42)—Concentrated nitric acid
(HNO ).
9. Summary of Practice
9.1 Samples are placed in loosely capped, heat-, and aci-
13. Procedures
dresistant containers with selected reagents and subjected to
121°C and 15 psig (103 kPa gage) for 30 min.After removing 13.1 In this section two types of digestion procedures are
any particulate matter remaining, the digestate is ready for
described: one for liquid samples (see 13.2) and one for solid
analysis by atomic absorption spectrophotometry, plasma and semi-solid samples (see 13.3).
emission spectroscopy, or plasma-mass spectrometry.
13.2 Liquid Samples:
9.2 The practice may be found to be more applicable to a 13.2.1 Using a sample volume from 40 to 100 mL, pipet an
particular sample or analytical scheme after appropriate modi-
aliquot of sample, hydrochloric acid, and nitric acid into a
fications of reagent addition, temperature, pressure, digestion digestion container in the following ratio: 100 volumes sample
time, or container selection. Any such modifications to this to 5 volumes HCl (sp gr 1.19) to 1 volume HNO (sp gr 1.42).
practice must be validated by the user. 13.2.2 Swirl digestion container gently to mix contents.
13.2.3 Loosely place caps on digestion containers and place
10. Apparatus
digestion containers in rack.
10.1 Digestion Containers—50 mL disposable polypropy-
NOTE 2—Caps should be attached securely enough so that they are not
lene centrifuge tubes and 125 mL polypropylene reagent
thrown off during autoclaving, but not so securely that gas is unable to
bottles with screw caps have been used successfully. Any
move freely in and out of the container.
container that is not attacked by the digestion conditions, is
13.2.4 Place rack of digestion containers in autoclave and
sufficiently free of the analyte(s) of interest, and can be loosely
process for 30 min. at 121°C and 15 psig (103 kPa gage).
capped, may be used.
13.2.5 Remove digestion containers from autoclave; allow
10.2 Digestion Container Rack—Any rack that will fit
to cool to room temperature.
inside the autoclave, will hold the digestion containers se-
13.2.6 Proceed with assay of digested sample.
curely, and is not attacked by the conditions in the autoclave,
may be used.
NOTE 3—Experience with this practice indicated that with sample and
10.3 Autoclave—Any autoclave or similar apparatus with a acid volumes in the ranges specified in 13.2.1 final volume after
autoclaving will approximate the original sample volume within 1 %. If,
pressure chamber large enough to hold the desired number of
after verifying this observation and determining if this degree of volu-
samples and capable of achieving and holding 121°C and 15
metric uncertainty is acceptable, the user may proceed to use the digestate
psig (103 kPa gage) for 30 min., may be employed. An
without any volume correction. In cases where the final volume after
autoclave with automatic cycling is desirable.As the digesting
autoclaving is not sufficiently close to the original sample volume,
samples release acidic fumes, the portions of the autoclave
experience indicates that the final volume will still be very reproducible.
coming in contact with these fumes should be constructed of
Inthesecasesandwherethefinaldigestatevolumeislessthantheoriginal
volume of sample, a fixed volume of water can be added to the digestate
acid resistant materials.
to make its volume closely approximate the original sample volume.
NOTE 1—Prolonged use of an autoclave with a stainless steel interior
Conversely, a sufficient volume of water can be added prior to autoclav-
for this practice may result in discoloration of the autoclave walls. This
ing, such that the final volume of digestate is close enough to the original
discoloration has not been shown to cause any problems with autoclave
sample volume.
operation. A commercially available autoc
...
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