ASTM D6832-2002 Standard Test Method for the Determination of Hexavalent Chromium in Workplace Air by Ion Chromatography and Spectrophotometric Measurement Using 1 5-diphenylcarbaz.pdf

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1、Designation: D 6832 02Standard Test Method forthe Determination of Hexavalent Chromium in Workplace Airby Ion Chromatography and SpectrophotometricMeasurement Using 1,5-diphenylcarbazide1This standard is issued under the fixed designation D 6832; the number immediately following the designation indi

2、cates the year oforiginal adoption 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 method specifies a method for t

3、he determina-tion of the time-weighted average mass concentration ofhexavalent chromium in workplace air.1.2 The method is applicable to the personal sampling of theinhalable fraction of airborne particles, as defined in ISO 7708,and to area (static) sampling.1.3 The sample dissolution procedure spe

4、cifies separateprocedures for soluble and insoluble hexavalent chromium.1.4 The method is applicable to the determination of massesof 0.01 g to 10 g of hexavalent chromium per samplewithout dilution.1.5 The concentration range for hexavalent chromium in airfor which this procedure is applicable is a

5、pproximately 0.1g/m3to 100 g/m3, assuming 1 m3of air sample. The rangecan be extended upwards by appropriate dilution.1.6 Interconversion of trivalent and hexavalent chromiumspecies may occur during sampling and sample preparation,but these processes are minimized to the extent possible by thesampli

6、ng and sample preparation procedures employed.1.7 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 safety and health practices and determine the applica-bility of regul

7、atory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterD 1605 Terminology Related to Atmospheric SamplingD 4840 Guide for Sampling Chain-of-Custody ProceduresE 882 Guide for Accountability and Quality Control in theChemical Analysis Laboratory

8、E 1370 Guide for Air Sampling Strategies for Worker andWorkplace Protection2.2 ISO Standards:3ISO 648 Laboratory Glassware One-mark PipetsISO 1042 Laboratory Glassware One-mark VolumetricFlasksISO 3585 Glass Plant, Pipeline and Fittings Properties ofBorosilicate Glass 3.3ISO 7708 Particle Size Defin

9、itions for Health-related Sam-plingISO 8655 Piston and/or Plunger-operated Volumetric Appa-ratus (6 Parts)3. Summary of Test Method3.1 A known volume of air is drawn through a filter tocollect particulate hexavalent chromium. The sampler is de-signed to collect the inhalable fraction of airborne par

10、ticles (seeISO 7708).3.2 The filter and collected sample are subjected to adissolution procedure in order to extract hexavalent chromium.The sample dissolution procedure may consist of one (or both)of two techniques: one for soluble and one for insolublehexavalent chromium.NOTE 1If it is desired to

11、measure both soluble as well as totalhexavalent chromium, the soluble procedure is used first, and this isfollowed by the procedure for insoluble hexavalent chromium com-pounds. Thus, total CrVI is the sum of soluble and insoluble hexavalentchromium compounds. On the other hand, if it is desired to

12、measure totalhexavalent chromium without first isolating insoluble CrVI compounds,only the procedure for insoluble CrVI is required (this will dissolve bothsoluble and insoluble hexavalent chromium compounds).3.2.1 For dissolution of soluble hexavalent chromium, dis-tilled water with no heating is u

13、sed to treat the sample.Alternatively, a weakly basic ammonium sulfate/ammonium1This test method is under the jurisdiction of ASTM Committee D22 onSampling and Analysis of Atmospheres and is the direct responsibility of Subcom-mittee D22.04 on Workplace Atmospheres.Current edition approved October 1

14、0, 2002. Published December 2002.2For 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 website.3Available from American Nat

15、ional Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.hydroxide buffer solution with no heating is used to extractsoluble forms of hexavalent chromium.3.2.2 For

16、 dissolution of insoluble hexavalent chromium, aweakly basic carbonate buffer solution with heating by a hotplate is used for sample treatment. Alternatively, an ultrasonicbath is used instead of a hot plate.3.3 Aliquots of sample extracts are subjected to ion chro-matography in order to separate ex

17、tracted hexavalent chro-mium from trivalent chromium and other metal cations. Anammonium sulfate/ammonium hydroxide eluent solution isused as the mobile phase.3.4 Following separation, hexavalent chromium is reactedwith an acidic solution of 1,5-diphenylcarbazide to form acharacteristic violet chrom

18、ium-diphenylcarbazone complex.Post-column derivatization is used in order to react hexavalentchromium with 1,5-diphenylcarbazide.3.5 The absorbance of the chromium-diphenylcarbazonecomplex is measured at 540 nm using visible spectrophotom-etry. Analytical results are obtained by plotting the measure

19、dabsorbance as a function of concentration of the chromium-diphenylcarbazone complex.3.6 The analysis results may be used for the assessment ofworkplace exposures to hexavalent chromium in air.4. Significance and Use4.1 Airborne hexavalent chromium is carcinogenic (1),4andanalytical methods for the

20、measurement of this species inworkplace aerosols are desired. Worker exposure to hexavalentchromium occurs primarily through inhalation (1), and this testmethod provides a means for exposure assessment to thishighly toxic species. Analytical results from this procedure canbe used for regulatory comp

21、liance purposes (2).5. Reactions5.1 Reduction of hexavalent chromium to trivalent speciescan occur in acidic environments, and also in the presence oforganic material or environments having high iron concentra-tions in air (3). Reduction of hexavalent chromium can alsooccur on filter media (4), and

22、efforts should to taken tominimize this contribution to sample loss. Oxidation of triva-lent chromium to hexavalent species can occur in strong baseand in the presence of air (5), so efforts should be taken tominimize these contributions to analytical bias. In plating mistsamples and in some welding

23、 fume samples, interference fromiron may be problematic (2).6. Apparatus6.1 Samplers, designed to collect the inhalable fraction ofairborne particles, for use when the exposure limits of interestapply to the inhalable fraction of airborne particles (as definedin ISO 7708).NOTE 2In general, personal

24、samples for collection of the inhalablefraction of airborne particles do not exhibit the same size selectivecharacteristics if used for area (static) sampling.NOTE 3Consider whether the sample is meant to constitute only thatmaterial which is collected on filter material, or whether the samplecompri

25、ses all particulate that is captured within the sampler (that is, allmaterial on the filter, backup pad (if applicable), and on the inside wallsof the sampler).6.2 Filters, of a diameter suitable for use with the samplers(6.1), with a collection efficiency of not less than 99.5 % forparticles with a

26、 0.3 m diffusion diameter (ISO 7708), andcompatible with the sample preparation and analysis method.NOTE 4Typical filter diameters for personal sampling are 25 mm and37 mm.6.2.1 Filters should not react with Cr(VI). The following areacceptable:6.2.1.1 Polyvinyl chloride (PVC) membrane filters,5mpore

27、 size or below.6.2.1.2 Polyvinyl fluoride (PVF) membrane filters,5mpore size or below.6.2.1.3 Polytetrafluorinated ethylene (PTFE) membrane fil-ters, 5 m pore size or below.6.2.1.4 Glass fiber filters, binder-free.6.2.1.5 Quartz fiber filters.6.2.1.6 PVC/acrylic copolymer membrane filters, 5 m pores

28、ize or less.NOTE 5Several types of filters have been found to cause reduction ofhexavalent chromium (4). Mixed cellulose ester (MCE) filters may causesignificant reduction of hexavalent chromium, and are generally unsuit-able. Some PVC filters have been reported to cause hexavalent chromiumreduction

29、; this should be investigated prior to choosing PVC filters.NOTE 6When sampling chromic acid mist, there is an advantage if theoxidizing potential of hexavalent chromium is lowered, for instance byimpregnating the filter with alkali. For example, this can be accomplishedby soaking the filter overnig

30、ht in 1 M sodium hydroxide, and allowing itto dry. This lessens the tendency of Cr(VI) to react with organiccompounds in the filter material, or reducing agents and dust present in thesampled air, or both. Filter materials such as PVC and PTFE can beunsuitable for alkali treatment since they tend to

31、 be hydrophobic andtherefore not easily wetted. PVF and vinyl/acrylic copolymer membranefilters have been found to be suitable for alkali treatment (3).6.3 Backup pads, if necessary for use in the particularsampler employed.NOTE 7Cellulose backup pads should not be used for sampling ofchromic acid m

32、ist, since droplets can penetrate the filter by capillary force,resulting in the possibility of Cr(VI) reduction with the backup padmaterial. Glass or quartz fiber backup pads could be used, or a meshcomprised of material that is resistant to chromic acid.6.4 Sampling pumps, with an adjustable flow

33、rate andcapable of maintaining the selected flow rate (between 1 and 5L/min for personal sampling pumps, and between 5 and 400L/min for high-volume sampling pumps) to within 65 % of thenominal value throughout the sampling period (up to 8-10 h forpersonal sampling, or shorter periods for high-volume

34、 sam-pling). For personal sampling the pumps shall be capable ofbeing worn by the worker without impeding normal workactivity. Sampling pump flow rates shall be calibrated usingeither a primary or secondary standard; if a secondary standardis used, it shall be calibrated using a primary standard.NOT

35、E 8A flow-stabilized pump may be required to maintain the flowrate within the specified limits.4The boldface numbers in parentheses refer to the list of references at the end ofthis test method.D68320226.5 Flowmeter, portable, capable of measuring the selectedvolumetric flow rate to within 62 %, and

36、 calibrated against aprimary standard (that is, a flowmeter whose accuracy istraceable to primary standards).6.6 Ancillary equipment:6.6.1 Flexible tubing, of a diameter suitable for making aleak-proof connection from the sampler to the sampling pump.6.6.2 Belts or harnesses, to which the sampling p

37、ump canbe conveniently fixed for personal sampling (except wheresampling pumps are small enough to fit inside workerspockets).6.6.3 Flat-tipped forceps, for loading and unloading filtersinto or out of samplers.6.6.4 Filter transport cassettes, or similar, if required, inwhich to transport samples fo

38、r laboratory analysis.6.6.5 Disposable gloves, for sample handling and preven-tion of sample contamination.6.7 Analytical or laboratory apparatusOrdinary laboratory apparatus, and:6.7.1 Glassware, made of borosilicate glass 3.3 and com-plying with the requirements of ISO 3585.6.7.1.1 Beakers, of cap

39、acities between 50 mL and 2 L.6.7.1.2 Watch glasses, to fit the beakers.6.7.1.3 One-mark pipets, complying with the requirementsof ISO 648.6.7.1.4 One-mark volumetric flasks, of capacities between10 mL and 1000 mL, complying with the requirements of ISO1042.6.7.1.5 Piston-operated volumetric apparat

40、us, complyingwith the requirements of ISO 8655. Pipettors, as an alternativeto one-mark pipets for the preparation of standard solutions,calibration solutions, and dilution of samples. Dispensors, fordispensing acids.6.7.2 Hot plate, thermostatically controlled, capable ofmaintaining a surface tempe

41、rature of approximately 135C; forhot plate extraction of insoluble hexavalent chromium com-pounds.6.7.3 Sonicator, minimum power output 0.5 W/cm2, for usein the ultrasonic extraction of insoluble hexavalent chromiumcompounds.6.7.4 Ion chromatograph, having the following compo-nents:NOTE 9The followi

42、ng components should be comprised, to the extentpossible, of inert materials.6.7.4.1 Pump, capable of delivering a constant flow in therange of 1 to 5 mL/min at a pressure of 15 to 150 MPa.6.7.4.2 Injection valve:A low dead-volume valve, (1 mL or less), nonmetallic, thatwill allow the loading of sam

43、ple contents into the eluantstream. Sample loops of up to 1 mL volume will provideenhanced detection limits.NOTE 10Either an autosampler or a manual injection system, or both,is (are) acceptable.6.7.4.3 Guard column:A column placed before the separator column (6.7.4.4)toprotect the separator column

44、from fouling by particles orstrongly adsorbed organic constituents.6.7.4.4 Separator column:A column packed with high capacity pellicular anion ex-change resin that is suitable for resolving hexavalent chromiumfrom other metals and cations.6.7.4.5 Reagent delivery module:A device capable of deliveri

45、ng 0 to 2 mL/min of reagentsolution against a back pressure of up to 40 kPa.6.7.4.6 Mixing tee and reaction coil:A device capable of mixing two flowing streams withminimal band spreading.6.7.4.7 Detector:Alow-volume flow-through visible absorbance detector witha nonmetallic flow path.6.7.4.8 Recorde

46、r, integrator or computer:Adevice compatible with detector output, capable of record-ing detector response as a function of time for the purpose ofmeasuring peak height or area.NOTE 11The use of an automated system is recommended.6.7.5 Eluant reservior:A container suitable for storing eluant solutio

47、n.6.7.6 Syringe filter, 0.45 m, for sample filtration prior toanalysis. The filter material shall be chemically inert.6.7.7 Syringe, equipped with a male fitting and a capacity ofat least 1 mL; or auto sampler module with like specifications.7. Reagents7.1 For the analysis of hexavalent chromium, us

48、e onlyreagents of recognized analytical grade, and only water asspecified in (7.1.1).7.1.1 Water, complying with the requirements of ASTMType 1 water (as specified in Specification D 1193: electricalconductivity less than 0.1 mS/m and resistivity greater than0.01 M-V-m at 25C).7.1.2 Sulfuric acid (H

49、2SO4), concentrated, specific gravity1.84 g/mL, 98 % (m/m).7.1.3 Nitric acid (HNO3), concentrated, specific gravity1.42 g/mL, 69-71 % (m/m).7.1.4 Nitric acid wash solution (1 % HNO3):Dilute 10 mL of concentrated nitric acid (7.1.3) to 1 litrewith water (7.1.1).7.1.5 Sodium carbonate (Na2CO3), anhydrous, puritygreater than 99.9 % (m/m).7.1.6 Sodium hydroxide (NaOH), pellets, purity greater than99.5 % (m/m).7.1.7 Ammonium sulfate (NH4)2SO4), purity greater than99.5 % (m/m).7.1.8 Ammonia (NH3), concentrated, specific gravity 0.90g/mL, 29 % (m/m).7.1.9