1、Designation: D4606 15Standard Test Method forDetermination of Arsenic and Selenium in Coal by theHydride Generation/Atomic Absorption Method1This standard is issued under the fixed designation D4606; the number immediately following the designation indicates the year oforiginal adoption or, in the c
2、ase of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method2covers the determination of totalarsenic and selenium in coal.1.2 The va
3、lues stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate s
4、afety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D346 Practice for Collection and Preparation of CokeSamples for Laboratory AnalysisD2013 Practice for Preparing Coal Samples for AnalysisD3173 Test Method for
5、 Moisture in the Analysis Sample ofCoal and CokeD3180 Practice for Calculating Coal and Coke Analysesfrom As-Determined to Different BasesD7582 Test Methods for Proximate Analysis of Coal andCoke by Macro Thermogravimetric Analysis3. Summary of Test Method3.1 Arsenic and selenium are determined by m
6、ixing aweighed coal sample with Eschka mixture and igniting at750 C. The mixture is dissolved in hydrochloric acid and thegaseous hydride of each element is generated from the appro-priate oxidation state and determined by atomic absorptionspectrophotometry.4. Significance and Use4.1 This test metho
7、d permits measurement of the totalarsenic and selenium content of coal for the purpose ofevaluating these elements where they can be of concern, forexample, in coal combustion. When coal samples are preparedfor analysis in accordance with this test method, the arsenicand selenium are quantitatively
8、retained and are representativeof the total amounts in the coal.5. Apparatus5.1 Atomic Absorption Spectrophotometer, with backgroundcorrection system and peak profile recording device.5.2 Hydride Generation Apparatus, for producing the hy-drides of arsenic and selenium.5.3 Burner or Heated Quartz Ce
9、ll, for thermal decomposi-tion of the hydrides.5.4 Hotplate, capable of maintaining a temperature of asolution at 60 C to 90 C.5.5 Ignition CruciblesPorcelain crucible of 30 mL capac-ity. Do not use a porcelain crucible in which the glaze is flaked.5.6 Analytical Balance, capable of weighing to a re
10、solutionof 0.0001 g.6. Reagents6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications
11、are available.41This test method is under the jurisdiction of ASTM Committee D05 on Coaland Coke and is the direct responsibility of Subcommittee D05.29 on MajorElements in Ash and Trace Elements of Coal.Current edition approved Nov. 1, 2015. Published December 2015. Originallyapproved in 1986. Last
12、 previous edition approved in 2007 as D4606 03(2007).DOI: 10.1520/D4606-15.2For information concerning experimental work on which this test method isbased see: Bosshart, R. E., Price, A. A., and Ford, C. T., “Evaluation of the Effectof Coal Cleaning on Fugitive Elements, Phase II Final Report, Part
13、II AnalyticalMethods,” ERDA Report No. C00-44727-35 , 1980, pp. 94102; Fernandez, F. J.,“Atomic Absorption Determination of Gaseous Hydrides Utilizing Sodium Boro-hydride Reduction,” Atomic Absorption Newsletter, Vol 12, No. 4, 1973, pp. 9397;and Brodie, K. G., “A Comparative StudyDetermining Arseni
14、c and Selenium byAAS,” American Laboratory , March 1977, pp. 7378.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM web
15、site.4Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Phar
16、macopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16.2 Purity of WaterUse high-purity, conductivity water,prepared by passing distilled water (or eq
17、uivalent) through anion exchange resin.6.3 Eschka MixturePrepare (with thorough mixing) amixture that has a mass fraction of 67 % light calcinedmagnesium oxide (MgO) and 33 % anhydrous sodium carbon-ate (Na2CO3). The mixture shall be as free as possible fromarsenic and selenium.6.4 Hydrochloric Acid
18、 Concentrated (sp gr 1.19)Concentrated hydrochloric acid (HCl).6.5 Hydrochloric Acid (1+4)Prepare a solution of diluteHCl in water with a volume fraction of 20 % of concentratedhydrochloric acid (HCl, sp gr 1.19).6.6 Potassium Iodide Solution 0.2 gmLDissolve 20 g ofpotassium iodide (KI) in 100 mL of
19、 water.6.7 Sodium Borohydride (Pellets or Solution)0.03 gmLTo dilute sodium hydroxide (NaOH) solution(0.01 gmL), add sodium borohydride (NaBH4) to give asolution that is 0.03 gmL sodium borohydride (NaBH4).Prepare fresh daily.6.8 Arsenic Stock Solution (1000 mgL Arsenic)Certifiedcommercially availab
20、le standard solution or prepared fromprimary standard arsenic trioxide (As2O3).6.9 Selenium Stock Solution (1000 mgL Selenium)Certified commercially available standard solution or preparedfrom selenium metal (99.99 %).7. Analysis Sample7.1 Obtain the sample for coal in accordance with MethodD2013 an
21、d the sample for coke in accordance with PracticeD346. Prepare the analysis sample by pulverizing the materialto pass a 250 m (No. 60) U.S.A. standard sieve.7.2 A separate portion of the analysis sample shall beanalyzed concurrently for moisture content in accordance withTest Method D3173 or Test Me
22、thods D7582.7.3 Use certified reference materials, such as the NationalInstitute of Standards and Technology (NIST) Standard Refer-ence Material (SRM) coals. SRM 1632d and SRM 163a5 aretwo different coal samples that have certified values for botharsenic and selenium. Results obtained by analyzing t
23、hesecoals for arsenic and selenium using the test methods describedherein can be used for checking analytical technique and testmethod accuracy. At least one SRM coal sample should beanalyzed as a control when a set of coal samples are analyzed.8. Sample Preparation and Solution8.1 To minimize the p
24、otential for contamination, clean alllabware thoroughly with dilute HCl solution (1 + 9) and rinsewith water. The hydride generation apparatus shall be keptequally clean.8.2 Weigh approximately1gofcoal into a preweighed30 mL crucible. Record the mass to the nearest 0.0001 g.Thoroughly mix the sample
25、 with 1.5 g of Eschka mixture andcover the mixture with an additional 1.5 g of Eschka mixture.Place the sample in a cold muffle furnace. Set the temperaturecontrol to 500 C. Heat the sample for 1 h. Increase the furnacetemperature to 750 C. Continue heating at this temperature for3 h. Remove the sam
26、ple and allow it to cool to roomtemperature.8.3 Add 20 mL to 30 mL of hot water to a 150 mL beaker.Transfer the contents of the crucible from 8.2 to the beaker.Add 5 mL of concentrated HCl to the crucible. Then slowlyand carefully, with the aid of a stirring rod, transfer the HCl tothe beaker. Rinse
27、 any remaining material in the crucible intothe beaker with water. Add 15 mL concentrated HCl in three5 mL portions to the crucible and transfer to the beaker. Swirlthe contents until the Eschka has dissolved (Note 1).Allow thesolution to cool to room temperature and transfer it to a100 mL polypropy
28、lene volumetric flask. Dilute to volume withwater.NOTE 1Some residue can remain.9. Blank9.1 Weigh 15 g of Eschka mixture into a crucible. Heat asdescribed in 8.2.Add 100 mLto 150 mLhot deionized water toa 500 mL beaker. Transfer the contents of the crucible to thebeaker. Add 25 mL concentrated HCl t
29、o the crucible. Thenslowly and carefully, with the aid of a stirring rod, transfer theHCl to the beaker. Rinse any remaining material in the crucibleinto the beaker with water. Add 75 mL concentrated HCl inthree 25 mL portions to the crucible and transfer to the beaker.Swirl the contents until the E
30、schka has dissolved (Note 1).Allow the solution to cool to room temperature and transfer toa 500 mL polypropylene volumetric flask. Dilute to volumewith water.10. Procedure for Arsenic10.1 The solutions and preparations described are typicalfor North American coals. Different solution concentrations
31、can be required to establish suitable analytical results for thoseelements with mass fractions outside the typical range. Eachanalyst shall determine the sensitivity and optimum method ofcalibration of their own equipment and choose standards withconcentration ranges compatible with the samples and
32、instru-ments specific to their work. Twenty millilitres is a normalworking volume for batch hydride generation systems. If ahydride generation system is designed to accommodate otherthan 20 mL(sample + acid), a different volume can be used andall reagents and sample volumes can be ratioed accordingl
33、y.10.2 Prepare an intermediate arsenic standard 1 mL to10 gmL from the stock solution. Prepare fresh daily. Preparea working standard (Note 2) by adding 1 mL of the interme-diate standard to a 100 mL polypropylene volumetric flask.Dilute to volume with blank (Section 9).NOTE 2Five millilitres of the
34、 working standard should produce asignal approximately in the middle of the linear dynamic range for theatomic absorption operating conditions chosen.10.3 Prepare three calibration standards by combining vol-umes of the working standard and blank solution that yield atotal volume equivalent to the a
35、nalytical volume (Av) (seeAnnex A1) in a reaction flask. Dilute to 20 mL with HCl(1 + 4).D4606 15210.4 Prepare a reagent blank by adding a volume of blanksolution equivalent to the analytical volume (Av) (see AnnexA1) to a reaction flask and dilute to 20 mL with HCl (1 + 4).10.5 Add 2 mL of potassiu
36、m iodide solution to the calibra-tion standards and blank. Allow the solutions to sit at ambienttemperature for 30 min.10.6 Use an arsenic hollow cathode or electrodeless dis-charge lamp and set the monochromator for 193.7 nm. Adjustinstrument parameters to optimum for the particular instrumentused.
37、10.7 Attach the reaction flask to the sampling system andintroduce either sodium borohydride pellets or solution andread out the peak response for the blank and each calibrationstandard. Either peak height or peak area can be used. Theoperator shall select the response that gives the maximumresponse
38、 per microgram of arsenic.10.8 Establish a calibration curve of micrograms of arsenicin the reaction flask versus peak response.10.9 Samples should be analyzed within 24 h of prepara-tion. Take an aliquot of sample solution that contains lessarsenic than the highest concentration calibration standar
39、d andmore arsenic than the lowest concentration calibration stan-dard. Dilute to the analytical volume (Av) (see AnnexA1) withblank solution and then to 20 mLwith HCl (1 + 4) to a reactionflask. Treat as in 10.5 10.7. Read out the peak response andestablish micrograms of arsenic in the aliquot of so
40、lutionanalyzed from the calibration curve.11. Procedure for Selenium11.1 Prepare an intermediate selenium standard taking noteof the provisions stated in 10.1 and using the same procedureas described for arsenic in 10.2.11.2 Prepare three calibration standards by combining vol-umes of the working st
41、andard and blank solution that yield atotal volume equivalent to the analytical volume (Av) (seeAnnex A1) in a 150 mL beaker.11.3 Prepare a reagent blank by adding a volume of blanksolution equivalent to the analytical volume (Av) (see AnnexA1) to a 150mL beaker.11.4 Add 10 mL of concentrated hydroc
42、hloric acid (HCl) tothe beakers. The solution temperature shall be maintainedbetween 60 C and 90 C. To monitor the solution temperature,place a thermometer in a beaker containing a volume of waterequivalent to the solution volume in the other beakers. Placethe beakers covered with watch glasses on a
43、 hot plate and heatfor 1 h. Allow the solutions to cool to room temperature.Transfer by rinsing with concentrated HCl where necessary toreaction flasks so that the final volume of solution in thereaction flask is 20 mL.11.5 Use a selenium hollow cathode or electrodeless dis-charge lamp and set the m
44、onochromator for 196.0 nm. Adjustinstrument parameters to optimum for the particular instrumentused.11.6 Analyze the sample using the procedure described forarsenic in 10.7.11.7 Calibrate using the same procedure as described forarsenic in 10.8.11.8 Samples should be analyzed within 24 h of preparat
45、ion.Take an aliquot of sample solution that contains less seleniumthan the highest concentration calibration standard and moreselenium than the lowest concentration calibration standard.Dilute to the analytical volume (Av) (see AnnexA1) with blanksolution in a 150 mL beaker. Treat the solution as in
46、 11.4 11.6. Establish micrograms of selenium in the aliquot ofsample solution analyzed from the selenium calibration curve.12. Calculations12.1 Calculation of arsenic mass fraction:As g/g coal db! 5 S 3100!/V 3 W! (1)where:As = arsenic g/g coal dry basis;S = arsenic in aliquot of solution analyzed,
47、g;100 = volume of solution from which aliquot was taken, mL;V = volume of sample aliquot analyzed, mL; andW = mass of dried coal, g.12.2 Calculation of selenium mass fraction:Se g/g coal db! 5 S 3100!/V 3 W! (2)where:Se = selenium g/g coal dry basis;S = selenium in aliquot of solution analyzed, g;10
48、0 = volume of solution from which aliquot was taken, mL;V = volume of sample aliquot analyzed, mL; andW = mass of dried coal, g.13. Report13.1 Report the value of arsenic or selenium obtained usingthe calculations specified in Section 12.13.2 Report the test method used for the concurrent mois-ture
49、determination.13.3 Report the value obtained, the certified value, andlimits for any CRM analyzed concurrently with the samples.14. Precision and Bias514.1 The precision of this test method for the determinationof Arsenic and Selenium in coal is shown in Table 1.5Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D05-1008.TABLE 1 Mass Fraction Range and Limits for Repeatability andReproducibility for Arsenic and Selenium in Coal.Mass FractionRange, g/gRepeatabilityLimi
