1、Designation: D 4606 03 (Reapproved 2007)Standard Test Method forDetermination of Arsenic and Selenium in Coal by theHydride Generation/Atomic Absorption Method1This standard is issued under the fixed designation D 4606; the number immediately following the designation indicates the year oforiginal a
2、doption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method2covers the determination of totalarsenic and seleni
3、um in coal.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.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 es
4、tablish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 121 Terminology of Coal and CokeD 346 Practice for Collection and Preparation of CokeSamples for Laboratory AnalysisD 2013 Practice fo
5、r Preparing Coal Samples for AnalysisD 3173 Test Method for Moisture in theAnalysis Sample ofCoal and CokeD 3180 Practice for Calculating Coal and Coke Analysesfrom As-Determined to Different BasesD 5142 Test Methods for Proximate Analysis of the Analy-sis Sample of Coal and Coke by Instrumental Pro
6、cedures3. Summary of Test Method3.1 Arsenic and selenium are determined by mixing aweighed coal sample with Eschka mixture and igniting at750C. The mixture is dissolved in hydrochloric acid and thegaseous hydride of each element is generated from the appro-priate oxidation state and determined by at
7、omic absorptionspectrophotometry.4. Significance and Use4.1 This test method 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 ac
8、cordance with this test method, the arsenicand selenium are quantitatively 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 pro
9、ducing the hy-drides of arsenic and selenium.5.3 Burner or Heated Quartz Cell, for thermal decomposi-tion of the hydrides.5.4 Hotplate, capable of maintaining a temperature of asolution at 60 to 90C.5.5 Ignition CruciblesPorcelain crucible of 30-mL capac-ity. Do not use porcelain crucible in which t
10、he glaze is flaked.5.6 Analytical Balance, capable of weighing to 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 t
11、he American Chemical Society,where such specifications are available.46.2 Purity of WaterUse high-purity, conductivity water,prepared by passing distilled water (or equivalent) through anion exchange resin.1This test method is under the jurisdiction of ASTM Committee D05 on Coaland Coke and is the d
12、irect responsibility of Subcommittee D05.29 on MajorElements in Ash and Trace Elements of Coal.Current edition approved Oct. 1, 2007. Published October 2007. Originallyapproved in 1986. Last previous edition approved in 2003 as D 4606 03.2For information concerning experimental work on which this te
13、st 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 II AnalyticalMethods,” ERDA Report No. C00-44727-35 , 1980, pp. 94102; Fernandez, F. J.,“Atomic Absorption Determination of Gaseous Hydri
14、des Utilizing Sodium Boro-hydride Reduction,” Atomic Absorption Newsletter, Vol 12, No. 4, 1973, pp. 9397;and Brodie, K. G., “A Comparative StudyDetermining Arsenic and Selenium byAAS,” American Laboratory , March 1977, pp. 7378.3For referenced ASTM standards, visit the ASTM website, www.astm.org, o
15、rcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the test
16、ing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor D
17、rive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.3 Eschka MixtureThoroughly mix two parts by weightof light calcined magnesium oxide (MgO) with one part byweight anhydrous sodium carbonate (Na2CO3). The mixtureshall be as free as possible from arsenic and selenium.6.4 Hydrochlori
18、c Acid Concentrated (sp gr 1.19)Concentrated hydrochloric acid (HCl).6.5 Hydrochloric Acid (1 + 4)Mix one volume of concen-trated hydrochloric acid (HCl, sp gr 1.19) with four volumes ofdeionized water.6.6 Potassium Iodide Solution 20 % (weight per volume)Dissolve 20 g of potassium iodide (KI) in 10
19、0 mL of deionizedwater.6.7 Sodium Borohydride (Pellets or Solution) 3 % (weightper volume)To a 1 % (weight per volume) sodium hydroxide(NaOH) solution, add sodium borohydride (NaBH4) to give asolution 3 % (weight per volume) sodium borohydride(NaBH4). Prepare fresh daily.6.8 Arsenic Stock Solution (
20、1000-ppm Arsenic)Certifiedcommercially available standard solution or prepared fromprimary standard arsenic trioxide (As2O3).6.9 Selenium Stock Solution (1000-ppm Selenium)Certified commercially available standard solution or preparedfrom selenium metal (99.99 %).7. Analysis Sample7.1 Obtain the sam
21、ple for coal in accordance with MethodD 2013 and the sample for coke in accordance with PracticeD 346. Prepare the analysis sample by pulverizing the materialto pass a 250-m (No. 60) U.S. standard sieve.7.2 A separate portion of the analysis sample shall beanalyzed concurrently for moisture content
22、in accordance withTest Method D 3173 or Test Methods D 5142.7.3 Use certified reference materials, such as the NationalInstitute of Standards and Technology (NIST) Standard Refer-ence Material (SRM) coals. SRM 1632b and SRM 1635 aretwo different coal samples which are currently available andhave cer
23、tified values for both arsenic and selenium. Resultsobtained by analyzing these coals for arsenic and seleniumusing the test methods described herein can be used forchecking analytical technique and test method accuracy. Atleast one SRM coal sample should be analyzed as a controlwhen a set of coal s
24、amples are analyzed.8. Sample Preparation and Solution8.1 To minimize the potential for contamination, clean alllabware thoroughly with dilute HCl solution (1 + 9) and rinsewith deionized water. The hydride generation apparatus shallbe kept equally clean.8.2 Weigh approximately1gofcoal into a prewei
25、ghed30-mL crucible. Record the weight to the nearest 0.0001 g.Thoroughly mix the sample 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 500C. Heat the sample for 1 h. Increase the fu
26、rnacetemperature to 750C. Continue heating at this temperature for3 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-mLbeaker. Transfer the contents of the crucible from 8.2 to thebeaker. Add 5 mL of concentrated HCl to the crucible. Then
27、slowly and carefully, with the aid of a stirring rod, transfer theHCl to the beaker. Rinse any remaining material in the crucibleinto the beaker with deionized water. Add 15-mL concentratedHCl in three 5-mL portions to the crucible and transfer to thebeaker. Swirl the contents until the Eschka has d
28、issolved (Note1). Cool the solution and transfer it to a 100-mL polypropylenevolumetric flask. Dilute to volume with deionized water.NOTE 1Some residue can remain.9. Blank9.1 Weigh 15 g of Eschka mixture into a crucible. Heat asdescribed in 8.2. Add 100- to 150-mL hot deionized water to a500-mL beak
29、er. Transfer the contents of the crucible to thebeaker. Add 25-mL concentrated HCl to 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 deionized water. Add 75-mL concentratedHCl in
30、three 25-mL portions to the crucible and transfer to thebeaker. Swirl the contents until the Eschka has dissolved (Note1). Cool the solution and transfer to a 500-mL polypropylenevolumetric flask. Dilute to volume with deionized water.10. Procedure for Arsenic10.1 The solutions and preparations desc
31、ribed are typicalfor North American coals. Different solution concentrationscan be required to establish suitable analytical results for thoseelements with concentrations outside the typical range. Eachanalyst shall determine the sensitivity and optimum method ofcalibration of their own equipment an
32、d choose standards withconcentration ranges compatible with the samples and 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 vol
33、ume can be used andall reagents and sample volumes can be ratioed accordingly.10.2 Prepare an intermediate arsenic standard 1 to 10 g/mLfrom the stock solution. Prepare fresh daily. Prepare a workingstandard (Note 2) by adding 1 mL of the intermediate standardto a 100-mL polypropylene volumetric fla
34、sk. Dilute to volumewith blank (Section 9).NOTE 2Five millilitres of the 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
35、standard and blank solution which yielda total volume equivalent to the analytical volume (Av) (seeAnnex A1) in a reaction flask. Dilute to 20 mL with HCl(1 + 4).10.4 Prepare a reagent blank by adding a volume of blanksolution equivalent to the analytical volume (Av) (see AnnexA1) to a reaction flas
36、k and dilute to 20 mL with HCl (1 + 4).10.5 Add 2 mL of potassium 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. Adjustins
37、trument parameters to optimum for the particular instrumentused.D 4606 03 (2007)210.7 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
38、can be used. Theoperator shall select the response which gives the maximumresponse 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 sol
39、ution which contains lessarsenic than the highest concentration calibration standard andmore arsenic than the lowest concentration calibration stan-dard. Dilute to the analytical volume ( Av) (seeAnnexA1) withblank solution and then to 20 mL with HCl (1 + 4) to a reactionflask. Treat as in 10.5-10.7
40、. Read out the peak response andestablish micrograms of arsenic in the aliquot of solutionanalyzed 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 1
41、0.2.11.2 Prepare three calibration standards by combining vol-umes of the working standard and blank solution which yielda total 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 analyti
42、cal volume (Av) (see AnnexA1) to a 150-mL beaker.11.4 Add 10 mL of concentrated hydrochloric acid (HCl) tothe beakers. The solution temperature shall be maintainedbetween 60 and 90C. To monitor the solution temperature,place a thermometer in a beaker containing a volume of waterequivalent to the sol
43、ution volume in the other beakers. Placethe beakers covered with watch glasses on a 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 m
44、L.11.5 Use a selenium hollow cathode or electrodeless dis-charge lamp and set the monochromator 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 d
45、escribed forarsenic in 10.8.11.8 Samples should be analyzed within 24 h of preparation.Take an aliquot of sample solution which contains less sele-nium than the highest concentration calibration standard andmore selenium than the lowest concentration calibration stan-dard. Dilute to the analytical v
46、olume (Av) (see Annex A1) withblank solution in a 150-mL beaker. Treat the solution as in11.4-11.6. Establish micrograms of selenium in the aliquot ofsample solution analyzed from the selenium calibration curve.12. Calculations12.1 Calculation of arsenic concentration:As g/g coal db!5S 3 100!/V 3 W!
47、 (1)where:As = arsenic g/g coal dry basis;S = arsenic in aliquot of solution analyzed, g;100 = volume of solution from which aliquot was taken,mL;V = volume of sample aliquot analyzed, mL; andW = weight of dried coal, g.12.2 Calculation of selenium concentration:Se g/g coal db!5S 3 100!/V 3 W! (2)wh
48、ere:Se = arsenic g/g coal dry basis;S = arsenic in aliquot of solution analyzed, g;100 = volume of solution from which aliquot was taken,mL;V = volume of sample aliquot analyzed, mL; andW = weight of dried coal, g.13. Report13.1 Report the value of arsenic or selenium obtained usingthe calculations
49、specified in Section 12.13.2 Report the test method used for the concurrent mois-ture 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 1.14.1.1 Repeatability Limit (r)the value below which theabsolute difference between two test results calculated to a drybasis (Practice D 3180) of separate and consecutive test deter-minations, carried out
