ASTM D4698-21

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
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Designation: D4698 − 92 (Reapproved 2013) D4698 − 21
Standard Practice for
Total Digestion of Sediment Samples for Chemical Analysis
of Various Metals
This standard is issued under the fixed designation D4698; 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
1.1 This practice covers two procedures for the total digestion of sediments for subsequent determination of metals by such
techniques as flame atomic absorption spectrophotometry, graphite-furnace atomic absorption spectrophotometry, atomic emission
spectroscopy, etc.
1.2 This practice is applicable in the subsequent determination of volatile, semivolatile, and nonvolatile metals of sediments.
1.3 Actual metal quantitation can be accomplished by following the various test methods outlined under other appropriate ASTM
standards for the metal(s) of interest. Before selecting either of the digestion techniques outlined in this practice, the user should
consult the appropriate quantitation standard(s) for any special analytical considerations, and Practice D3976 for any special
preparatory considerations.
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.5 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. For a specific hazard statement, see Note 715.5.
1.5 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information
only.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1129 Terminology Relating to Water
D1192 Guide for Equipment for Sampling Water and Steam in Closed Conduits (Withdrawn 2003)
This practice is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.07 on Sediments, Geomorphology, and
Open-Channel Flow.
Current edition approved Jan. 1, 2013Nov. 1, 2021. Published January 2013January 2022. Originally approved in 1987. Last previous edition approved in 20072013 as
D4698 – 92 (2007).(2013). DOI: 10.1520/D4698-92R13.10.1520/D4698-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’sstandard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
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D4698 − 21
D1193 Specification for Reagent Water
D3976 Practice for Preparation of Sediment Samples for Chemical Analysis
3. Terminology
3.1 Definitions—Definitions: For definitions of terms used in this practice, refer to Terminology D1129.
3.1.1 For definitions of terms used in this standard, refer to Terminology D1129.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 total digestion—partial digestion, n—the dissolution of a sediment matrix such that quantitation will produce a measurement
which is more of less than 95 % of the constituent present in the sample. In such cases, recovery is operationally defined by the
digestion procedure.
3.2.2 partial digestion—total digestion, n—the dissolution of a sediment matrix such that quantitation will produce a measurement
of less which is more than 95 % of the constituent present in the sample. In such cases, recovery is operationally defined by the
digestion procedure.
4. Summary of Practice
4.1 Many procedures are available for the total digestion of sediments prior to metal analysis, but almost all the methods fall into
one of two main classes: fusion and subsequent dissolution of the bead, and wet digestion which directly dissolves the sample with
mineral acids. Each of the classes has advantages and disadvantages, as do the individual procedures which fall under them. The
two procedures outlined in this practice were selected because they are the least restricted, in terms of utility, for dealing with a
wide variety of matrices. Before choosing a particular method, the user should consult the pertinent literature to determine the
, ,
utility and applicability of either method, prior to final selection; or if a less rigorous digestion could be employed.employed ( 1-4).
4,
Even then, experience with a particular sample type or digestion test method, or both, may have to be the final arbiter in test
method selection.
4.2 Field collected samples should be treated according to the procedures outlined in Practice D3976.
4.3 Dried samples are ground to finer than 100 mesh (150 μm) using an appropriate grinding device or system.
4.4 Procedure A—Fusion with lithium metaborate/tetraborate.
4.5 Procedure B—Wet digestion using a combination of hydrofluoric, perchloric, and nitric acids.
5. Significance and Use
5.1 The chemical analysis of sediments, collected from such locations as streams, rivers, lakes, and oceans can provide
information of environmental significance.
5.2 These practices can be used with either suspended sediment (material actively transported by water) or bed sediment (material
temporarily at rest on the bed of a water body).
5.3 Standardized practices for digesting sediments, for subsequent chemical analysis, will facilitate inter- and intra-areal
comparisons as well as comparison of data generated by different groups. The use of total digestions also eliminates the ambiguities
and interpretational difficulties associated with partial digestions and the operational definitions that accompany them.
Johnson, W., and Maxwell, J.,The boldface numbers in parentheses Rock and Mineral Analysis,refer to a list 2nd Edition, John Wiley & Sons, New York, 1981, p. 489.of
references at the end of this standard.
Pinta, M., Modern Methods for Trace Element Analysis, Ann Arbor Science Publishers, Ann Arbor, 1982, pp. 133–264.
Dolezal, J., Povondra, C., and Sulcek, Z., Decomposition Techniques in Inorganic Analysis, Elsevier Publishing Co., New York, 1968, pp. 11–157.
Shapiro, L., “Rapid Analysis of Silicate, Carbonate, and Phosphate Rocks,” Revised Edition, U.S. Geological Survey Bulletin, 1401, 1975, p. 76.
D4698 − 21
PROCEDURE A—FUSION
6. Scope
6.1 This procedure is effective for the total digestion of suspended and bottom sediments for the subsequent determination of
aluminum, calcium, iron, magnesium, potassium, manganese, silicon, sodium, and titanium.
6.2 This practice may be appropriate for the subsequent determination of other metals provided the concentrations are high enough
or if the instrumental sensitivity is sufficient.
7. Interferences
7.1 Numerous inter-element interferences, both positive and negative, exist for this procedure and have been amply documented
,
elsewhere.elsewhere (1, 2).
7.2 Interferences are eliminated or compensated for, or both, through the use of cesium chloride (CsCl), orthoboric acid (H BO ),
3 3
lithium metaborate (LiBO ), lithium tetraborate (Li B O ), and the use of mixed salt standards during quantitation by flame atomic
2 2 4 7
absorption spectrophotometry.
8. Apparatus
8.1 Graphite Crucibles, drill point, with a 7.5-mL capacity and a 1-in. (25.4 mm) outside diameter, ⁄4-in. (19.05 mm) inside
diameter, and total depth of 1 ⁄8 in. (34.925 mm).
8.2 Magnetic Stirrer.
8.3 Muffle Furnace, capable of reaching a temperature of at least 1000°C.
9. Reagents
9.1 Purity of Reagents—Reagent grade chemicals shall be used in all digestions. Unless otherwise indicated, it is intended that all
reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such
specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity
to permit its use without lesseningreducing the accuracy of the subsequent quantitation.
9.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by Type
II of Specification D1193.
9.3 Mixed Salt Standards—The mixed salt standards are provided as a guide to the user for use with atomic absorption analyses
to reduce matrix and interelement interferences. They have been found effective for the constit-uents listed in 6.1. They may have
to be modified to accommodate others.
9.4 Cesium Chloride, Solution (4 g/L)—Dissolve 4 g of CsCl in water and dilute to 1 L.
9.5 Diluent Solution—Dissolve 6 g of flux mixture in 500 mL of water. Add 12.5 mL concentrated nitric acid (sp gr 1.41), and
dilute to 1 L with water.
9.6 Flux Mixture—Thoroughly mix 1 part powdered anhydrous lithium metaborate, LiBO , and 2 parts anhydrous lithium
tetraborate, Li B O . Store in a tightly closed bottle.
2 4 7
Reagent Chemicals, American Chemical Society Specifications,ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference
Materials, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for
Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC),
Rockville, MD.
D4698 − 21
NOTE 1—It is possible to purchase pre-mixed fusion fluxes from several suppliers, and provided they are of sufficient purity, have been found quite
satisfactory.
9.7 Mixed Metals Solution, Stock—Dissolve by appropriate means, the following compounds, elements, or both: aluminum metal
(1.500 g), calcium carbonate (1.249 g), iron metal (1.000 g), magnesium metal (0.200 g), manganese metal (0.040 g), KCl (0.668
g), ammonium hexafluorosilicate (18.987 g), NaCl (0.636 g), and ammonium titanyl oxalate (1.227 g), and dilute to 1000 mL with
diluent solution (9.5). This solution will contain the following concentrations: aluminum (1500 mg/L), calcium (500 mg/L), iron
(1000 mg/L), magnesium (200 mg/L), manganese (40 mg/L), potassium (350 mg/L), silica (3000 mg/L), sodium (250 mg/L), and
titanium (200 mg/L). Store in a plastic or TFE-fluorocarbon bottle.
9.8 Mixed Metals Solutions, Standards 1, 2, and 3—Take respectively, a 10-, 6-, and 2-mL aliquot of the mixed metals stock
solution (9.7), and dilute to 100 mL in volumetric glassware with standard diluent solution (9.5). Concentrations are given in Table
1.
9.9 Nitric Acid, concentrated (sp gr 1.41).
9.10 Nitric Acid (1 + 1)—Add 250 mL of concentrated nitric acid (sp gr 1.41) to 250 mL water. Store in a plastic bottle.
9.11 Orthoboric Acid Solution (50 g/L)—Dissolve 50 g of H BO in water and dilute to 1 L. Heat may be required to complete
3 3
dissolution. Prepare fresh daily because orthoboric acid may precipitate within 12 to 18 h.
10. Procedure
10.1 Immediately before each use, clean all glassware by rinsing first with HNO (1 + 1), and then with water.
10.2 Dry the sediment sample by an appropriate procedure such as freeze-drying, or oven drying at 105°C (see Practice D3976).
10.3 If the sediment sample is greater than 100 g, split it to less than 100 g by the use of a nonmetallic sample splitter (riffle
sampler) or by coning and quartering.
10.4 Grind the sample with an appropriate system until all material is finer than 100 mesh (150 μm).
10.5 Transfer approximately 1.2 g of flux mixture to a waxed or plastic-coated weighing paper (6 in. by 6 in. (152.4 mm by 152.4
mm)). Weigh and transfer 0.2000 g of finely ground sample to the flux mixture and mix by rolling successive corners of the paper
about 30 times. Carefully transfer the combined sample/flux to a graphite crucible, and tamp down by gently tapping the crucible
on a tabletop.
10.6 Weigh appropriate sediment or rock standards and treat as in 10.5.
10.7 Carry several blanks through the procedure by using only flux and treat as in 10.5.
TABLE 1 Concentrations of Mixed Metals
Solutions 1, 2, and 3
Standard 1, Standard 2, Standard 3,
mg/L mg/L mg/L
Volume (mL) 10 6 2
Iron 100 60 20
Magnesium 20 12 4
Silicon 300 180 60
Aluminum 150 90 30
Titanium 20 12 4
Calcium 50 30 10
Sodium 25 15 5
Potassium 35 21 7
Manganese 4 2 1
D4698 − 21
10.8 Fuse the mixtures in a muffle furnace, preheated to 1000°C, for 30 min.
NOTE 2—When the crucibles, samples, and crucible racks are placed in the muffle furnace, the temperature may drop as much as 200°C. Time is still
measured from the time of insertion in the furnace.
10.9 Remove the crucibles from the furnace and allow to cool; dislodge the beads by gentle tapping or with a spatula.
NOTE 3—The beads can be dissolved immediately after cooling, or can be stored in plastic vials for dissolution at a later time.
10.10 Place the bead in an acid-washed 250-mL plastic bottle and add a ⁄4 to 1 in. (19.05 to 25.4 mm) magnetic stirring bar. Add
approximately 50-mL boiling water using a plastic graduate, place the bottle on a magnetic stirrer, and mix. Add 5 mL of HNO
(1 + 1) to each bottle and stir rapidly for about 60 min. Cap the bottle lightly to prevent both contamination and possible spattering.
10.11 Immediately after 60 min, remove the bottles from the stirrers, and add about 100 mL of water to prevent th
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