ASTM D4698-92(2001)
(Practice)Standard Practice for Total Digestion of Sediment Samples for Chemical Analysis of Various Metals
Standard Practice for Total Digestion of Sediment Samples for Chemical Analysis of Various Metals
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 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. For a specific hazard statement, see Note 7.
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.
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Designation:D4698–92(Reapproved2001)
Standard Practice for
Total Digestion of Sediment Samples for Chemical Analysis
of Various Metals
This standard is issued under the fixed designation D 4698; 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 3. Terminology
1.1 This practice covers two procedures for the total diges- 3.1 Definitions—For definitions of terms used in this prac-
tion of sediments for subsequent determination of metals by tice, refer to Terminology D 1129.
suchtechniquesasflameatomicabsorptionspectrophotometry, 3.2 Definitions of Terms Specific to This Standard:
graphite-furnace atomic absorption spectrophotometry, atomic 3.2.1 total digestion—the dissolution of a sediment matrix
emission spectroscopy, etc. such that quantitation will produce a measurement which is
1.2 This practice is applicable in the subsequent determina- more than 95 % of the constituent present in the sample.
tion of volatile, semivolatile, and nonvolatile metals of sedi- 3.2.2 partial digestion—the dissolution of a sediment ma-
ments. trix such that quantitation will produce a measurement of less
1.3 Actual metal quantitation can be accomplished by fol- than 95 % of the constituent present in the sample. In such
lowing the various test methods outlined under other appropri- cases, recovery is operationally defined by the digestion
ate ASTM standards for the metal(s) of interest. Before procedure.
selecting either of the digestion techniques outlined in this
4. Summary of Practice
practice, the user should consult the appropriate quantitation
4.1 Many procedures are available for the total digestion of
standard(s) for any special analytical considerations, and Prac-
tice D 3976 for any special preparatory considerations. sediments prior to metal analysis, but almost all the methods
fall into one of two main classes: fusion and subsequent
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the dissolution of the bead, and wet digestion which directly
dissolves the sample with mineral acids. Each of the classes
responsibility of the user of this standard to establish appro-
has advantages and disadvantages, as do the individual proce-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. For a specific dures which fall under them. The two procedures outlined in
this practice were selected because they are the least restricted,
hazard statement, see Note 7.
1.5 The values stated in inch-pound units are to be regarded in terms of utility, for dealing with a wide variety of matrices.
Before choosing a particular method, the user should consult
as the standard. The values given in parentheses are for
information only. the pertinent literature to determine the utility and applicability
of either method, prior to final selection; or if a less rigorous
4,5,6,7
2. Referenced Documents
digestion could be employed. Even then, experience with
2.1 ASTM Standards: a particular sample type or digestion test method, or both, may
D 1129 Terminology Relating to Water have to be the final arbiter in test method selection.
D 1192 Specification for Equipment for Sampling Water 4.2 Field collected samples should be treated according to
and Steam in Closed Conduits the procedures outlined in Practice D 3976.
D 1193 Specification for Reagent Water 4.3 Dried samples are ground to finer than 100 mesh (150
D 3976 Practice for Preparation of Sediment Samples for µm) using an appropriate grinding device or system.
Chemical Analysis
Johnson, W., and Maxwell, J., Rock and Mineral Analysis, 2nd Edition, John
This practice is under the jurisdiction of ASTM Committee D19 on Water and Wiley & Sons, New York, 1981, p. 489.
is the direct responsibility of Subcommittee D19.07 on Sediments, Geomorphology, Pinta, M., Modern Methods for Trace Element Analysis, Ann Arbor Science
and Open-Channel Flow. Publishers, Ann Arbor, 1982, pp. 133–264.
Current edition approved Oct. 15, 1992. Published December 1992. Originally Dolezal, J., Povondra, C., and Sulcek, Z., Decomposition Techniques in
published as D 4698 – 87. Last previous edition D 4698 – 87. Inorganic Analysis, Elsevier Publishing Co., New York, 1968, pp. 11–157.
2 7
Annual Book of ASTM Standards, Vol 11.01. Shapiro, L., “Rapid Analysis of Silicate, Carbonate, and Phosphate Rocks,”
Annual Book of ASTM Standards, Vol 11.02. Revised Edition, U.S. Geological Survey Bulletin, 1401, 1975, p. 76.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D4698–92 (2001)
4.4 Procedure A—Fusion with lithium metaborate/ where such specifications are available. Other grades may be
tetraborate. used, provided it is first ascertained that the reagent is of
sufficiently high purity to permit its use without lessening the
4.5 Procedure B—Wet digestion using a combination of
accuracy of the subsequent quantitation.
hydrofluoric, perchloric, and nitric acids.
9.2 Purity of Water—Unless otherwise indicated, references
to water shall be understood to mean reagent water as defined
5. Significance and Use
by Type II of Specification D 1193.
5.1 Thechemicalanalysisofsediments,collectedfromsuch
9.3 Mixed Salt Standards—The mixed salt standards are
locations as streams, rivers, lakes, and oceans can provide
provided as a guide to the user for use with atomic absorption
information of environmental significance.
analyses to reduce matrix and interelement interferences. They
5.2 These practices can be used with either suspended
have been found effective for the constit-uents listed in 6.1.
sediment (material actively transported by water) or bed
They may have to be modified to accommodate others.
sediment (material temporarily at rest on the bed of a water
9.4 Cesium Chloride, Solution (4 g/L)—Dissolve4gof
body).
CsCl in water and dilute to 1 L.
9.5 Diluent Solution—Dissolve6gofflux mixture in 500
5.3 Standardized practices for digesting sediments, for sub-
mLofwater.Add12.5mLconcentratednitricacid(spgr1.41),
sequent chemical analysis, will facilitate inter- and intra-areal
and dilute to 1 L with water.
comparisons as well as comparison of data generated by
9.6 Flux Mixture—Thoroughly mix 1 part powdered anhy-
different groups. The use of total digestions also eliminates the
drous lithium metaborate, LiBO , and 2 parts anhydrous
ambiguities and interpretational difficulties associated with
lithium tetraborate, Li B O . Store in a tightly closed bottle.
partial digestions and the operational definitions that accom-
2 4 7
pany them.
NOTE 1—Itispossibletopurchasepre-mixedfusionfluxesfromseveral
suppliers, and provided they are of sufficient purity, have been found quite
PROCEDURE A—FUSION satisfactory.
9.7 Mixed Metals Solution, Stock—Dissolve by appropriate
6. Scope
means, the following compounds, elements, or both: aluminum
metal (1.500 g), calcium carbonate (1.249 g), iron metal (1.000
6.1 This procedure is effective for the total digestion of
g), magnesium metal (0.200 g), manganese metal (0.040 g),
suspended and bottom sediments for the subsequent determi-
KCl (0.668 g), ammonium hexafluorosilicate (18.987 g), NaCl
nation of aluminum, calcium, iron, magnesium, potassium,
(0.636 g), and ammonium titanyl oxalate (1.227 g), and dilute
manganese, silicon, sodium, and titanium.
to 1000 mL with diluent solution (9.5). This solution will
6.2 This practice may be appropriate for the subsequent
contain the following concentrations: aluminum (1500 mg/L),
determination of other metals provided the concentrations are
calcium (500 mg/L), iron (1000 mg/L), magnesium (200
high enough or if the instrumental sensitivity is sufficient.
mg/L), manganese (40 mg/L), potassium (350 mg/L), silica
(3000 mg/L), sodium (250 mg/L), and titanium (200 mg/L).
7. Interferences
Store in a plastic or TFE-fluorocarbon bottle.
7.1 Numerous inter-element interferences, both positive and
9.8 Mixed Metals Solutions, Standards 1, 2, and 3—Take
negative, exist for this procedure and have been amply docu-
respectively, a 10-, 6-, and 2-mL aliquot of the mixed metals
4,5
mented elsewhere.
stock solution (9.7), and dilute to 100 mL in volumetric
glassware with standard diluent solution (9.5). Concentrations
7.2 Interferencesareeliminatedorcompensatedfor,orboth,
are given in Table 1.
through the use of cesium chloride (CsCl), orthoboric acid
9.9 Nitric Acid, concentrated (sp gr 1.41).
(H BO ), lithium metaborate (LiBO ), lithium tetraborate
3 3 2
9.10 Nitric Acid (1 + 1)—Add 250 mL of concentrated
(Li B O ), and the use of mixed salt standards during quanti-
2 4 7
nitric acid (sp gr 1.41) to 250 mL water. Store in a plastic
tation by flame atomic absorption spectrophotometry.
bottle.
9.11 Orthoboric Acid Solution (50 g/L)—Dissolve 50 g of
8. Apparatus
H BO in water and dilute to 1 L. Heat may be required to
3 3
8.1 Graphite Crucibles, drill point, with a 7.5-mL capacity
complete dissolution. Prepare fresh daily because orthoboric
and a 1-in. (25.4 mm) outside diameter, ⁄4-in. (19.05 mm)
acid may precipitate within 12 to 18 h.
inside diameter, and total depth of 1 ⁄8 in. (34.925 mm).
10. Procedure
8.2 Magnetic Stirrer.
8.3 Muffle Furnace, capable of reaching a temperature of at 10.1 Immediately before each use, clean all glassware by
least 1000°C. rinsing first with HNO (1 + 1), and then with water.
9. Reagents
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
9.1 Purity of Reagents—Reagent grade chemicals shall be
listed by the American Chemical Society, see Analar Standards for Laboratory
usedinalldigestions.Unlessotherwiseindicated,itisintended
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
thatallreagentsconformtothespecificationsoftheCommittee
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
on Analytical Reagents of the American Chemical Society MD.
D4698–92 (2001)
TABLE 1 Concentrations of Mixed Metals
10.12 Pour each solution into a 200-mL volumetric flask,
Solutions 1, 2, and 3
using a funnel, in order to retain the stirring bar. Rinse the
Standard 1, Standard 2, Standard 3,
bottle and cap, and bring to the mark with water. Pour the
mg/L mg/L mg/L
solution back into the plastic bottle for storage.
Volume (mL) 10 6 2
10.13 Add 10 mL of CsCl solution and 20 mL of H BO
3 3
Iron 100 60 20
solution to each bottle.
Magnesium 20 12 4
Silicon 300 180 60
NOTE 5—The CsCl acts as an ionization suppressant and the H BO
3 3
Aluminum 150 90 30
stabilizes the silica; these are used when quantitation is by flame atomic
Titanium 20 12 4
Calcium 50 30 10 absorption spectrophotometry.
Sodium 25 15 5
10.14 Prepare the mixed metals standard solutions (see 9.8)
Potassium 35 21 7
Manganese 4 2 1
and to each 100 mL, add 5 mLof CsCl solution, and 10 mLof
H BO solution (Note 5).
3 3
10.15 See the appropriate ASTM test methods for subse-
quent quantitation.
10.2 Dry the sediment sample by an appropriate procedure
such as freeze-drying, or oven drying at 105°C (see Practice PROCEDURE B—WET DIGESTION
D 3976).
11. Scope
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
11.1 This procedure is effective for the total digestion of
(riffle sampler) or by coning and quartering.
suspended and bottom sediments for the subsequent determi-
10.4 Grind the sample with an appropriate system until all
nation of aluminum, calcium, iron, magnesium, manganese,
material is finer than 100 mesh (150 µm).
potassium, sodium, titanium, strontium, lithium, copper, zinc,
10.5 Transfer approximately 1.2 g of flux mixture to a
cadmium, lead, cobalt, nickel, chromium, arsenic, antimony,
waxed or plastic-coated weighing paper (6 in. by 6 in. (152.4
and selenium.
mm by 152.4 mm)). Weigh and transfer 0.2000 g of finely
11.2 This practice may be appropriate for the subsequent
ground sample to the flux mixture and mix by rolling succes-
determination of other metals provided the concentrations are
sive corners of the paper about 30 times. Carefully transfer the
high enough or if the instrumental sensitivity is sufficient.
combined sample/flux to a graphite crucible, and tamp down
by gently tapping the crucible on a tabletop. 12. Interferences
10.6 Weighappropriatesedimentorrockstandardsandtreat
12.1 Numerous inter-element interferences, both positive
as in 10.5.
and negative, exist for this procedure and have been docu-
4, 5, 9
10.7 Carry several blanks through the procedure by using
mented elsewhere.
only flux and treat as in 10.5.
12.2 Interferences are eliminated, compensated for, or both,
10.8 Fuse the mixtures in a muffle furnace, preheated to
through the use of cesium chloride (CsCl), the use of mixed
1000°C, for 30 min.
salt standards, and background correction if quantitation is by
atomic absorption spectroscopy.
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
13. Apparatus
still measured from the time of insertion in the furnace.
13.1 TFE-Fluorocarbon Beakers, 100-mL capacity, thick
10.9 Remove the crucibles from the furnace and allow to
wall, capable of withstanding temperature up to 260°C.
cool; dislodge the beads by gentle tapping or with a spatula.
13.2 Hot Plate, electric or gas, capable of reaching at least
NOTE 3—The beads can be dissolved immediately after cooling, or can
250°C.
be stored in plastic vials for dissolution at a later time.
13.3 Perchloric Acid Hood, with appropriate washdown
facility and gas or electric outlets.
10.10 Place the bead in an acid-washed 250-mL plastic
bottleandadda ⁄4to1in.(19.05to25.4mm)magneticstirring
14. Reagents
bar. Add approximately 50-mL boiling water using a plastic
graduate, place the bottle on a magnetic stirrer, and mix. Add
14.1 Purity of Reagents—See 9.1.
5mLofHNO (1 + 1) to each bottle and stir rapidly for about
14.2 Purity of Water—See 9.2.
60 min. Cap the bottle lightly to prevent both contamination
14.3 The mixed salt standards are provided as a guide to the
and possible spattering.
user for use with atomic absorption analyses to reduce matrix
10.11 Immediatelyafter60min,removethebottlesfromthe and interelement interferences.They have been found effective
stirrers, and add about 100 mL of water to prevent the
for the constituents listed in 11.1.
...
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