ASTM D4606-95(2000)
(Test Method)Standard Test Method for Determination of Arsenic and Selenium in Coal by the Hydride Generation/Atomic Absorption Method
Standard Test Method for Determination of Arsenic and Selenium in Coal by the Hydride Generation/Atomic Absorption Method
SCOPE
1.1 This test method covers the determination of total arsenic and selenium in coal.
1.2 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.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: D 4606 – 95 (Reapproved 2000)
Standard Test Method for
Determination of Arsenic and Selenium in Coal by the
Hydride Generation/Atomic Absorption Method
This standard is issued under the fixed designation D 4606; 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 4. Significance and Use
1.1 This test method covers the determination of total 4.1 This test method permits measurement of the total
arsenic and selenium in coal. arsenic and selenium content of coal for the purpose of
1.2 This standard does not purport to address all of the evaluating these elements where they can be of concern, for
safety concerns, if any, associated with its use. It is the example, in coal combustion. When coal samples are prepared
responsibility of the user of this standard to establish appro- for analysis in accordance with this test method, the arsenic
priate safety and health practices and determine the applica- and selenium are quantitatively retained and are representative
bility of regulatory limitations prior to use. of the total amounts in the coal.
2. Referenced Documents 5. Apparatus
2.1 ASTM Standards: 5.1 Atomic Absorption Spectrophotometer, with background
D 121 Terminology of Coal and Coke correction system and peak profile recording device.
D 346 Practice for Collection and Preparation of Coke 5.2 Hydride Generation Apparatus, for producing the hy-
Samples for Laboratory Analysis drides of arsenic and selenium.
D 2013 Method of Preparing Coal Samples for Analysis 5.3 Burner or Heated Quartz Cell, for thermal decomposi-
D 3173 Test Method for Moisture in the Analysis Sample of tion of the hydrides.
Coal and Coke 5.4 Hotplate, capable of maintaining a temperature of a
D 3180 Practice for Calculating Coal and Coke Analyses solution at 60 to 90°C.
from As-Determined to Different Bases 5.5 Ignition Crucibles—Porcelain crucible of 30-mL capac-
D 5142 Test Methods for Proximate Analysis of the Analy- ity. Do not use porcelain crucible in which the glaze is flaked.
sis Sample of Coal and Coke by Instrumental Procedures 5.6 Analytical Balance, capable of weighing to 0.0001 g.
3. Summary of Test Method 6. Reagents
3.1 Arsenic and selenium are determined by mixing a 6.1 Purity of Reagents—Reagent grade chemicals shall be
weighed coal sample with Eschka mixture and igniting at used in all tests. Unless otherwise indicated, it is intended that
750°C. The mixture is dissolved in hydrochloric acid and the all reagents shall conform to the specifications of the Commit-
gaseous hydride of each element is generated from the appro- tee on Analytical Reagents of the American Chemical Society,
priate oxidation state and determined by atomic absorption where such specifications are available.
spectrophotometry. 6.2 Purity of Water—Use high-purity, conductivity water,
prepared by passing distilled water (or equivalent) through an
ion exchange resin.
6.3 Eschka Mixture—Thoroughly mix two parts by weight
This test method is under the jurisdiction of ASTM Committee D05 on Coal
of light calcined magnesium oxide (MgO) with one part by
and Coke and is the direct responsibility of Subcommittee D05.29 on Major
weight anhydrous sodium carbonate (Na CO ). The mixture
2 3
Elements in Ash and Trace Elements of Coal.
shall be as free as possible from arsenic and selenium.
Current edition approved Sept. 10, 1995. Published April 1996. Originally
e1
published as D 4606 – 86. Last previous edition D 4606 – 86 (1991) .
6.4 Hydrochloric Acid Concentrated (sp gr 1.19)—
For information concerning experimental work on which this test method is
Concentrated hydrochloric acid (HCl).
based see: Bosshart, R. E., Price, A. A., and Ford, C. T., “Evaluation of the Effect
of Coal Cleaning on Fugitive Elements, Phase II Final Report, Part II Analytical
Methods,” ERDA Report No. C00-44727-35, 1980, pp. 94–102; Fernandez, F. J.,
Reagent Chemicals, American Chemical Society Specifications, American
“Atomic Absorption Determination of Gaseous Hydrides Utilizing Sodium Boro-
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
hydride Reduction,” Atomic Absorption Newsletter, Vol 12, No. 4, 1973, pp. 93–97;
listed by the American Chemical Society, see Analar Standards for Laboratory
and Brodie, K. G., “A Comparative Study—Determining Arsenic and Selenium by
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
AAS,” American Laboratory, March 1977, pp. 73–78.
3 and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
Annual Book of ASTM Standards, Vol 05.06.
MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 4606
6.5 Hydrochloric Acid (1 + 4)—Mix one volume of concen- volumetric flask. Dilute to volume with deionized water.
trated hydrochloric acid (HCl, sp gr 1.19) with four volumes of
NOTE 1—Some residue can remain.
deionized water.
6.6 Potassium Iodide Solution 20 % (weight per volume)—
9. Blank
Dissolve 20 g of potassium iodide (KI) in 100 mL of deionized
9.1 Weigh 15 g of Eschka mixture into a crucible. Heat as
water.
described in 8.2. Add 100- to 150-mL hot deionized water to a
6.7 Sodium Borohydride (Pellets or Solution) 3 % (weight
500-mL beaker. Transfer the contents of the crucible to the
per volume)—To a 1 % (weight per volume) sodium hydroxide
beaker. Add 25-mL concentrated HCl to the crucible. Then
(NaOH) solution, add sodium borohydride (NaBH ) to give a
slowly and carefully, with the aid of a stirring rod, transfer the
solution 3 % (weight per volume) sodium borohydride
HCl to the beaker. Rinse any remaining material in the crucible
(NaBH ). Prepare fresh daily.
into the beaker with deionized water. Add 75-mL concentrated
6.8 Arsenic Stock Solution (1000-ppm Arsenic)—Certified
HCl in three 25-mL portions to the crucible and transfer to the
commercially available standard solution or prepared from
beaker. Swirl the contents until the Eschka has dissolved (Note
primary standard arsenic trioxide (As O ).
2 3
1). Cool the solution and transfer to a 500-mL polypropylene
6.9 Selenium Stock Solution (1000-ppm Selenium)—
volumetric flask. Dilute to volume with deionized water.
Certified commercially available standard solution or prepared
from selenium metal (99.99 %).
10. Procedure for Arsenic
10.1 The solutions and preparations described are typical
7. Analysis Sample
for North American coals. Different solution concentrations
7.1 Obtain the sample for coal in accordance with Method
can be required to establish suitable analytical results for those
D 2013 and the sample for coke in accordance with Practice
elements with concentrations outside the typical range. Each
D 346. Prepare the analysis sample by pulverizing the material
analyst shall determine the sensitivity and optimum method of
to pass a 250-μm (No. 60) U.S. standard sieve.
calibration of their own equipment and choose standards with
7.2 A separate portion of the analysis sample shall be
concentration ranges compatible with the samples and instru-
analyzed concurrently for moisture content in accordance with
ments specific to their work. Twenty millilitres is a normal
Test Method D 3173 or Test Methods D 5142.
working volume for batch hydride generation systems. If a
7.3 Use certified reference materials, such as the National
hydride generation system is designed to accommodate other
Institute of Standards and Technology (NIST) Standard Refer-
than 20 mL (sample + acid), a different volume can be used and
ence Material (SRM) coals. SRM 1632b and SRM 1635 are
all reagents and sample volumes can be ratioed accordingly.
two different coal samples which are currently available and
10.2 Prepare an intermediate arsenic standard 1 to 10 μg/mL
have certified values for both arsenic and selenium. Results
from the stock solution. Prepare fresh daily. Prepare a working
obtained by analyzing these coals for arsenic and selenium
standard (Note 2) by adding 1 mL of the intermediate standard
using the test methods described herein can be used for
to a 100-mL polypropylene volumetric flask. Dilute to volume
checking analytical technique and test method accuracy. At
with blank (Section 9).
least one SRM coal sample should be analyzed as a control
NOTE 2—Five millilitres of the working standard should produce a
when a set of coal samples are analyzed.
signal approximately in the middle of the linear dynamic range for the
atomic absorption operating conditions chosen.
8. Sample Preparation and Solution
8.1 To minimize the potential for contamination, clean all 10.3 Prepare three calibration standards by combining vol-
labware thoroughly with dilute HCl solution (1 + 9) and rinse umes of the working standard and blank solution which yield
with deionized water. The hydride generation apparatus shall a total volume equivalent to the analytical volume (Av) (see
be kept equally clean. Annex A1) in a reaction flask. Dilute to 20 mL with HCl
8.2 Weigh approximately1gof coal into a preweighed (1 + 4).
30-mL crucible. Record the weight to the nearest 0.0001 g. 10.4 Prepare a reagent blank by adding a volume of blank
Thoroughly mix the sample with 1.5 g of Eschka mixture and solution equivalent to the analytical volume (Av) (see Annex
cover the mixture with an additional 1.5 g of Eschka mixture. A1) to a reaction flask and dilute to 20 mL with HCl (1 + 4).
Place the sample in a cold muffle furnace. Set the temperature 10.5 Add 2 mL of potassium iodide solution to the calibra-
tion standards and blank. Allow the solutions to sit at ambient
control to 500°C. Heat the sample for 1 h. Increase the furnace
temperature to 750°C. Continue heating at this temperature for temperature for 30 min.
10.6 Use an arsenic hollow cathode or electrodeless dis-
3 h. Remove the sample and allow to cool to room temperature.
8.3 Add 20 to 30 mL of hot deionized water to a 150-mL charge lamp and set the monochromator for 193.7 nm. Adjust
beaker. Transfer the contents of the crucible from 8.2 to the instrument parameters to optimum for the particular instrument
beaker. Add 5 mL of concentrated HCl to the crucible. Then used.
slowly and carefully, with the aid of a stirring rod, transfer the 10.7 Attach the reaction flask to the sampling system and
HCl to the beaker. Rinse any remaining material in the crucible introduce either sodium borohydride pellets or solution and
into the beaker with deionized water. Add 15-mL concentrated read out the peak response for the blank and each calibration
HCl in three 5-mL portions to the crucible and transfer to the standard. Either peak height or peak area can be used. The
beaker. Swirl the contents until the Eschka has dissolved (Note operator shall select the response which gives the maximum
1). Cool the solution and transfer it to a 100-mL polypropylene response per microgram of arsenic.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 4606
10.8 Establish a calibration curve of micrograms of arsenic
100 = volume of solution from which aliquot was taken,
in the reaction flask versus peak response.
mL;
10.9 Samples should be analyzed within 24 h of prepara- V = volume of sample aliquot analyzed, mL; and
W = weight of dried coal, g.
tion. Take an aliquot of sample solution which contains less
arsenic than the highest concentration calibration standard and 12.2 Calculation of selenium concentration:
more arsenic than the lowest concentration calibration stan-
Se ~μg/g coal db!5 S 3 100!/ V 3 W! (2)
~ ~
dard. Dilute to the analytical volume ( Av) (see Annex A1) with
where:
blank solution and then to 20 mL with HCl (1 + 4) to a reaction
Se = arsenic μg/g coal dry basis;
flask. Treat as in 10.5-10.7. Read out the peak response and
S = arsenic in aliquot of solution analyzed, μg;
establish micrograms of arsenic in the aliquot of solution
100 = volume of solution from which aliquot was taken,
analyzed from the calibration curve.
mL;
V = volume of sample aliquot analyzed, mL; and
11. Procedure for Selenium
W = weight of dried coal, g.
11.1 Prepare an intermediate selenium standard taking note
13. Report
of the provisions stated in 10.1 and using the same procedure
as described for arsenic in 10.2.
13.1 Report the value of arsenic or selenium obtained using
11.2 Prepare three calibration standards by combining vol-
the calculations specified in Section 12.
umes of the working standard and blank solution which yield
13.2 Report the test method used for the concurrent mois-
a total volume equivalent to the analytical volume (Av) (see
ture determination.
Annex A1) in a 150-mL beaker.
13.3 Report the value obtained, the certified value, and
11.3 Prepare a reagent blank by adding a volume of blank limits for any CRM analyzed concurrently with the samples.
solution equivalent to the analytical volume (Av) (see Annex
14. Precision and Bias
A1) to a 150-mL beaker.
14.1 This test method is dependent upon the calibration of
11.4 Add 10 mL of concentrated hydrochloric acid (HCl) to
the equipment and the closeness of the standards to the samples
the beakers. The solution temperature shall be maintained
in content of the element of interest.
between 60 and 90°C. To monitor the solution temperature,
14.2 Precision Statement for Arsenic:
place a thermometer in a beaker containing a volume of water
14.2.1 The relative precision of this test method for the
equivalent to the solution volume in the other beakers. Place
determination of total arsenic covers the concentration range
the beakers covered with watch glasses on a hot plate and heat
from 0.7 to 12.2 parts per million on a dry basis.
for 1 h. Allow the solutions to cool to room temperature.
14.2.2 Repeatability—The difference in absolute value be-
Transfer by rinsing with concentrated HCl where necessary to
tween two consecutive test results carried out on two separate
reaction flasks so that the final volume of solution in the
test portions of the same sample of 60-mesh coal calculated to
reaction flask is 20 mL.
the dry basis in the same laboratory by the same operator using
11.5 Use a selenium hollow cathode or electrodeless dis-
the same apparatus should not exceed the repeatability interval
charge lamp
...
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