1、Designation: C 1219 05Standard Test Methods forArsenic in Uranium Hexafluoride1This standard is issued under the fixed designation C 1219; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in paren
2、theses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods are applicable to the determinationof total arsenic in uranium hexafluoride (UF6) by atomicabsorption spectrometry. Two test metho
3、ds are given: TestMethod AArsine Generation-Atomic Absorption (Sections5-10), and Test Method BGraphite Furnace Atomic Absorp-tion (Appendix X1).1.2 The test methods are equivalent. The limit of detectionfor each test method is 0.1 g As/g U when using a samplecontaining 0.5 to 1.0 g U. Test Method B
4、 does not have thecomplete collection details for precision and bias data thus themethod appears as an appendix.1.3 Test Method A covers the measurement of arsenic inuranyl fluoride (UO2F2) solutions by converting arsenic toarsine and measuring the arsine vapor by flame atomic absorp-tion spectromet
5、ry.1.4 Test Method B utilizes a solvent extraction to removethe uranium from the UO2F2solution prior to measurement ofthe arsenic by graphite furnace atomic absorption spectrom-etry.1.5 Both insoluble and soluble arsenic are measured whenUF6is prepared according to Test Method C 761.1.6 This standar
6、d 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 safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM
7、 Standards:2C 761 Test Methods for Chemical, Mass Spectrometric,Spectrochemical, Nuclear, and Radiochemical Analysis ofUranium HexafluorideC 787 Specification for Uranium Hexafluoride for Enrich-mentD 1193 Specification for Reagent Water3. Summary of Test Methods3.1 Arsine Generation-Atomic Absorpti
8、on SpectrometyMethodThe sample of UF6is hydrolyzed and the UO2F2solution is fumed with sulfuric acid in the presence of boricacid to complex the fluoride. Potassium iodide is used toreduce arsenic(V) to arsenic(III). Sodium borohydride is usedto generate arsine vapor in a hydride generator with subs
9、equentmeasurement by flame atomic absorption spectrometry.3.2 Graphite Furnace Atomic Absorption SpectrometryMethodThe sample of UF6is hydrolyzed, and the uranium inthe UO2F2solution is removed by extraction with tri(2-ethyl-hexyl)phosphate/heptane. The aqueous phase containing thearsenic is analyze
10、d by graphite furnace atomic absorption.4. Significance and Use4.1 Arsenic compounds are suspected to cause corrosion insome materials used in UF6handling equipment. Arsenicoriginates as a contaminant in fluorspar (CaF2) used to produceanhydrous hydrogen fluoride which is used subsequently in thepro
11、duction of UF6.4.2 These test methods are used to measure the arseniccontent in UO2F2solutions prepared from the hydrolysis ofUF6for determination of conformance to Specification C 787.TEST METHOD AARSINE GENERATION-ATOMICABSORPTION SPECTROMETRY5. Interferences5.1 The presence of hydrofluoric acid i
12、n the sample sup-presses arsine generation when using sodium borohydride.Boric acid is added to complex the fluoride present at a molarexcess of 250 %.35.2 Arsenic(V) must be reduced to arsenic(III) otherwisearsine will not be generated using sodium borohydride andhydrochloric acid.5.3 The reduction
13、 of arsenic(V) by potassium iodide is timedependent at room temperature requiring strict adherence to theprocedure.1This test methods are under the jurisdiction of ASTM Committee C26 onNuclear Fuel Cycle and are the direct responsibility of Subcommittee C26.05 onMethods of Tests.Current edition appr
14、oved August 1, 2005. Published September 2005. Originallyapproved in 1992. Last previous edition approved in 1997 as C 1219 92 (1997).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume info
15、rmation, refer to the standards Document Summary page onthe ASTM website.3Petrik, K., and Krivan, V., “Radiotracer Investigation of the Interference ofHydrofluoric Acid in the Determination of Arsenic and Antimony by HydrideGenerationAtomicAbsorption Spectroscopy,” Analytical Chemistry, Vol 59, No.
16、20(1987), pp. 24262427.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.4 Do not use platinum labware.6. Apparatus6.1 Atomic Absorption Spectrometer, equipped with anair-acetylene burner, arsenic hollow cathode lamp and hydridegener
17、ator, gas/liquid separator, and hydride absorption cell.6.2 Hot Plate, capable of reaching a surface temperature of500C.7. Reagents and Materials7.1 Reagents:7.1.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform
18、 to the specifications of the Committee onAnalytical Reagents of the American Chemical Society, wheresuch specifications are available.4Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe dete
19、rmination.7.1.2 Purity of WaterUnless otherwise indicated, refer-ences to water shall mean reagent water Type II conforming toSpecification D 1193.7.1.3 Acetylene (C2H2), 99.6 % minimum purity.7.1.4 Air, compressed breathing air or equivalent.7.1.5 Arsenic Standard Stock Solution (1000 mg As/L)Disso
20、lve 1.320 g of arsenic trioxide (As2O3) in 100 mL ofhydrochloric acid (1 + 2) and dilute to 1 L. Commerciallyavailable stock solutions traceable to NIST primary standardsmay be used.7.1.6 Arsenic Standard Solution (0.10 mg As/L)Pipet 10mL of 1000 mg/L arsenic stock solution into a 1-L volumetricflas
21、k containing 500 mL of water. Add 20 mL of concentratedhydrochloric acid, dilute to volume with water and mix. This(10 mg/L) solution should be kept no longer than one month.Pipet 2 mL of the 10 mg/L arsenic solution into a 200-mLvolumetric flask containing 100 mL of water. Add 4 mL ofconcentrated h
22、ydrochloric acid and dilute to volume withwater.NOTE 1The 0.10-mg As/L solution must not be kept longer than oneday.7.1.7 Boric Acid (H3BO3).7.1.8 Hydrochloric Acid (sp gr 1.18)Concentrated hydro-chloric acid (HCl).7.1.9 Hydrochloric Acid (1 + 1)Add one volume of con-centrated hydrochloric acid to o
23、ne volume of water.7.1.10 Hydrochloric Acid (1 + 2)Add one volume of con-centrated hydrochloric acid to two volumes of water.7.1.11 Nitrogen (N2), 99.9 % minimum purity.7.1.12 Potassium Iodide Solution (50 % w/v)Dissolve 50g of potassium iodide in water and dilute to 100 mL in avolumetric flask. Sto
24、re in a brown bottle.NOTE 2The colorless solution is stable for two days. A yellow tingeindicates the solution has deteriorated.7.1.13 Sodium Borohydride Solution (6.0 g/L)Dissolve3.0 g of sodium borohydride (NaBH4) and 2.5 g of sodiumhydroxide (NaOH) in water and dilute to 500 mL in avolumetric fla
25、sk. This solution should be prepared weekly.7.1.14 Sulfuric Acid (sp gr 1.84)Concentrated sulfuricacid (H2SO4).8. Calibration and Standardization8.1 Instrument ParametersA set of suggested atomicabsorption operating parameters is listed in Tables 1 and 2. Theparameters may vary with the type of inst
26、rument used and themanufacturers instructions.8.2 Preparation of Calibration Solutions:8.2.1 Aliquot 0, 2, 5, 10, 20, and 30 mL of the 0.10 mgAs/Lsolution into 100-mL volumetric flasks. Add 2 mL concen-trated H2SO4and 10 mL concentrated HCl to each flask.8.2.2 Add 2 mL of 50 % potassium iodide solut
27、ion anddilute to volume with water 75 min before running thecalibration solutions.8.3 Calibration:8.3.1 Follow the manufacturers directions to calibrate theinstrument. Use the following arsenic calibration solutionswith a 30-s water rinse between each solution: 0, 0.002, 0.005,0.010, 0.020, and 0.03
28、0 mg As/L. If the AA is manuallycontrolled, record the absorbances.8.3.2 With a microprocessor-controlled instrument, generatethe calibration curve using the manufacturers directions. Thecalibration curve can also be generated manually by graphingthe absorbance of the calibration solutions on the or
29、dinate andthe corresponding concentration on the abscissa.8.3.3 Verify the calibration by running the mid-range 0.010mg As/L calibration solution. If the value differs by more than5 %, repeat the calibration.9. Procedure9.1 Sample Preparation:9.1.1 Prepare a hydrolyzed UF6solution within a concen-tr
30、ation range of 50 to 250 g/L U using the appropriate sectionsof Test Method C 761.4“Reagent Chemicals, American Chemical Society Specifications,” AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see “Reagent Chemicals an
31、d Standards,”by Joseph Rosin, D. Van Nostrand Company, Inc., New York, New York, and the“United States Pharmacopeia.”TABLE 1 Atomic Absorption Operating ParametersElement arsenicWavelength, nm 193.7Lamp current, mA 10Slit width, nm 0.5Gas C2H2/airAcetylene, psig 9Air, psig 40Argon, psig 50Fuel flow,
32、 L/min 1.5Oxidant flow, L/min 4.0TABLE 2 Hydride Generator Operating ParametersSample flow, mL/min 8Hydrochloric acid flow, mL/min 1Sodium borohydride flow, mL/min 1C12190529.1.2 Transfer an aliquot of UO2F2solution containingapproximately 0.5 g of uranium into a 125-mL Erlenmeyerflask.9.1.3 Add 0.5
33、 g of H3BO3and 2 mL of concentrated H2SO4to the sample.9.1.4 Heat the sample at 325C until the acid starts to fume.Increase the hot plate temperature to 385C. When the samplefumes vigorously, increase the temperature to 500C and heatuntil the acid fumes lift above the solution.9.1.5 Remove sample fr
34、om hot plate and cool to roomtemperature.9.1.6 Quantitatively transfer the sample into a 100-mLvolumetric flask and add 10 mL concentrated HCl.9.1.7 Add 2 mL of potassium iodide solution (50 % w/v)and dilute to volume with water. Allow a minimum of 75 minat room temperature for the reaction to occur
35、.9.2 Quality Control:9.2.1 Prepare one reagent blank with each batch of samples.9.2.2 Transfer a duplicate aliquot of one sample from eachbatch into a 125-mL Erlenmeyer flask. Spike this sample witha known amount of arsenic based on the expected concentra-tion of the sample.9.2.3 Take the reagent bl
36、ank and the spiked sample throughprocedure steps 9.1.3-9.1.7.9.3 Sample Measurement:9.3.1 Measure the arsenic content in the samples aftercalibration of the instrument as outlined in Section 8.9.3.2 Record the concentration for calculation in Section 10.With an instrument which is not microprocessor
37、-controlled,record the absorbance and determine the concentration fromthe calibration graph.9.3.3 Use a 30-s water rinse between samples if runningseveral samples. After 10 samples verify the calibration byrunning the midrange calibration solution again. If the valuedeviates by more than 5 %, repeat
38、 the calibration and measurethe samples again.10. Calculation10.1 Calculate the arsenic concentration using the followingequation:g As/g U 5A 3 BC 3 D3 1000 (1)where:A = aliquot concentration (mg As/L) from the calibrationcurve using the sample absorbance,B = dilution volume, mL,C = sample aliquot s
39、ize, mL, andD = uranium concentration of sample, g/L.11. Precision and Bias11.1 PrecisionThe within laboratory precision for TestMethodAis shown in Table 3. The data for Test MethodAwascollected over a 10 month period in one laboratory by 4technicians. The samples were taken through the entire TestM
40、ethod A.11.2 BiasNo standard material certified for As in UF6isavailable. To determine bias estimates for Test Method A,uranyl fluoride solutions were spiked with NIST traceablestandard materials. The bias estimates are indicated in Table 4.12. Keywords12.1 arsenic; arsine; arsine generation; atomic
41、 absorptionspectrometry; graphite furnace; uranium hexafluoride; uranylfluoride; Zeeman background correctionAPPENDIX(Nonmandatory Information)X1. TEST METHOD BGRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRYX1.1 InterferencesX1.1.1 Fluoride interferes with the extraction process andmust be removed b
42、y evaporation with nitric acid.X1.1.2 Molecular (nonatomic) absorption interferences arecorrected by Zeeman background correction.X1.1.3 Chlorides may cause loss of arsenic in the dryingstep.X1.2 ApparatusX1.2.1 Graphite Furnace Atomic Absorption Spectrometerwith Zeeman Background Correction:X1.2.1.
43、1 Wavelength Source, either a hollow cathode lampor electrodeless discharge lamp to provide arsenic emissionlines.TABLE 3 Within Laboratory PrecisionTestMethodConcentration,g As/g UStandardDeviation% RSDNumber ofDeterminationsA 0.35 0.033 9.4 303.76 0.23 6.1 3013.60 0.69 5.0 30TABLE 4 Bias Estimates
44、TestMethodg As/g U MeanBiasEstimateNumber ofDeterminationsA 1.996 1.909 0.087 20C1219053X1.2.1.2 Stabilized temperature platform furnace tubes andplatforms.X1.3 Reagents and MaterialsX1.3.1 Reagents:X1.3.1.1 Purity of ReagentsReagent grade chemicalsshall be used in all tests. Unless otherwise indica
45、ted, it isintended that all reagents conform to the specifications of theCommittee on Analytical Reagents of the American ChemicalSociety, where such specifications are available.4Other gradesmay be used, provided it is first ascertained that the reagent isof sufficiently high purity to permit its u
46、se without lesseningthe accuracy of the determination.X1.3.1.2 Purity of WaterUnless otherwise indicated, ref-erences to water shall be understood to mean reagent water asdefined by Type II of Specification D 1193.X1.3.1.3 Arsenic Standard Solution (0.1 mg/L)Use 1000mg/L certified aqueous standard.
47、Dilute 5 mL of 1000 mg/Lsolution in 500 mL water with 1 mL HNO3. This solution willbe 10 mg/L arsenic. From the 10 mg/L solution, dilute 5 mLinto 500 mL water to prepare a 0.1-mg/L solution.NOTE X1.1Prepare 0.1-mg/L solution daily.X1.3.1.4 Arsenic Standard Stock Solution (1000 mg/L)Certified aqueous
48、 standard traceable to NIST primary stan-dards.X1.3.1.5 Heptane, high purity.X1.3.1.6 Nickel Nitrate Solution (5 % Ni w/v)Dissolve24.780 g of Ni(NO3)26H2O in water and dilute to 100 mL ina volumetric flask.X1.3.1.7 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO3).X1.3.1.8 Nitric Acid (1 + 3)Ad
49、d one part by volumeconcentrated HNO3to three parts water.X1.3.1.9 TEHP-Heptane Solution (1 + 1)Mix equal vol-umes of TEHPand heptane (500 mLeach) in a large separatoryfunnel. Add 100 mL concentrated HNO3and shake vigorouslyto wash the organic layer. Let stand and drain the acid layer.Repeat with rinsewater until the water pH is 3.0.X1.3.1.10 Tri(2-ethyl-hexyl)phosphate (TEHP)Technicalgrade.X1.4 Calibration and StandardizationX1.4.1 Instrument ParametersA set of suggested param-eters for the atomic absorption instrument and the graphitefu
