1、Designation: D 6832 08Standard 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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method specifies a method for th
3、e determina-tion of the time-weighted average mass concentration ofhexavalent chromium in workplace air samples.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 proced
4、ure specifies 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 applicab
5、le is approximately 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 th
6、esampling 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 o
7、f regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterD 1356 Terminology Relating to Sampling and Analysis ofAtmospheresD 3195 Practice for Rotameter CalibrationD 4840 Guide for Sample Chain-of-Custody ProceduresE 882 Guide for Account
8、ability and Quality Control in theChemical Analysis LaboratoryE 1370 Guide for Air Sampling Strategies for Worker andWorkplace Protection2.2 ISO Standards:3ISO 648 Laboratory GlasswareOne-mark PipetsISO 1042 Laboratory GlasswareOne-mark VolumetricFlasksISO 3585 Glass Plant, Pipeline and FittingsProp
9、erties ofBorosilicate Glass 3.3ISO 7708 Particle Size Definitions 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
10、de-signed to collect the inhalable fraction of airborne particles (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
11、for insolublehexavalent chromium.NOTE 1If it is desired to 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 hexavalent
12、chromium compounds. On the other hand, if it is desired to 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
13、 hexavalent chromium, dis-tilled water with no heating is used to treat the sample.Alternatively, a weakly basic ammonium sulfate/ammonium1This test method is under the jurisdiction of ASTM Committee D22 on AirQuality and is the direct responsibility of Subcommittee D22.04 on Workplace AirQuality.Cu
14、rrent edition approved Aug. 1, 2008. Published September 2008. Originallyapproved in 2002. Last previous edition approved in 2002 as D 6832 - 02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards
15、volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA
16、19428-2959, United States.hydroxide buffer solution with no heating is used to extractsoluble forms of hexavalent chromium.3.2.2 For dissolution of insoluble hexavalent chromium, aweakly basic carbonate buffer solution with heating by a hotplate is used for sample treatment. Alternatively, an ultras
17、onicbath is used instead of a hot plate.3.3 Aliquots of sample extracts are subjected to ion chro-matography in order to separate extracted hexavalent chro-mium from trivalent chromium and other metal cations. Anammonium sulfate/ammonium hydroxide eluent solution isused as the mobile phase.3.4 Follo
18、wing separation, hexavalent chromium is reactedwith an acidic solution of 1,5-diphenylcarbazide to form acharacteristic violet chromium-diphenylcarbazone complex.Post-column derivatization is used in order to react hexavalentchromium with 1,5-diphenylcarbazide.3.5 The absorbance of the chromium-diph
19、enylcarbazonecomplex is measured at 540 nm using visible spectrophotom-etry. Analytical results are obtained by plotting the measuredabsorbance as a function of concentration of the chromium-diphenylcarbazone complex.3.6 The analysis results may be used for the assessment ofworkplace exposures to he
20、xavalent chromium in air.4. Significance and Use4.1 Airborne hexavalent chromium is carcinogenic (1),4andanalytical methods for the measurement of this species inworkplace aerosols are desired. Worker exposure to hexavalentchromium occurs primarily through inhalation (1), and this testmethod provide
21、s a means for exposure assessment to thishighly toxic species. Analytical results from this procedure canbe used for regulatory compliance purposes (2).5. Reactions5.1 Reduction of hexavalent chromium to trivalent speciescan occur in acidic environments, and also in the presence oforganic material o
22、r environments having high iron concentra-tions in air (3). Reduction of hexavalent chromium can alsooccur on filter media (4), and 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
23、of air (5), so efforts should be taken tominimize these contributions to analytical bias. In plating mistsamples and in some welding fume samples, interference fromiron may be problematic (3).6. Apparatus6.1 Samplers, designed to collect the inhalable fraction ofairborne particles, for use when the
24、exposure limits of interestapply to the inhalable fraction of airborne particles (as definedin ISO 7708).NOTE 2In general, personal samples for collection of the inhalablefraction of airborne particles do not exhibit the same size selectivecharacteristics if used for area (static) sampling.NOTE 3Con
25、sider whether the sample is meant to constitute only thatmaterial which is collected on filter material, or whether the samplecomprises 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). See App
26、endix X1 for guidance on handling of walldeposits within sampling cassettes.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 0.3 m diffusion diameter (ISO 7708), andcompatible with the sample preparation and
27、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 size or below.6.2.1.2 Polyvinyl fluoride (PVF) membrane filters,5mpore size or belo
28、w.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 poresize or less.NOTE 5Several types of filters have been found to cause reduction ofhexa
29、valent 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; this should be investigated prior to choosing PVC filters.NOTE 6When sampling chro
30、mic 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 overnight in 1 M sodium hydroxide, and allowing itto dry. This lessens the tendency of Cr(V
31、I) 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 be hydrophobic andtherefore not easily wetted. PVF and vinyl/acrylic copolymer memb
32、ranefilters 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 mist, since droplets can penetrate the filter by capillary force,resulting in the pos
33、sibility 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 rate andcapable of maintaining the selected flow rate (between 1 and 5L/min for pers
34、onal 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 sam-pling). For personal sampling the pumps shall be capable ofbeing worn by the wo
35、rker 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 (seeD 3195).NOTE 8A flow-stabilized pump may be required to maintain the flow4The boldf
36、ace numbers in parentheses refer to the list of references at the end ofthis test method.D6832082rate within the specified limits.6.5 Flowmeter, portable, capable of measuring the selectedvolumetric flow rate to within 62 %, and calibrated against aprimary standard (that is, a flowmeter whose accura
37、cy 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 pump canbe conveniently fixed for personal sampling (except wheresampling
38、 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 for laboratory analysis.6.6.5 Disposable gloves, for sample handling and p
39、reven-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 capacities between 50 mL and 2 L.6.7.1.2 Watch glasses, to fit the beakers.
40、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 ofISO 1042.6.7.1.5 Piston-operated volumetric apparatus, complyingwith the requirements of ISO 8655. Pipettors, as an alterna
41、tiveto 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 temperature of approximately 135C; forhot plate extraction of insoluble hexav
42、alent 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 following components should be comprised, to the extentpossible, of inert mater
43、ials.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 sample contents into the eluantstream. Sample loops of up to 1 mL volume wi
44、ll 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 from fouling by particles orstrongly adsorbed organic constituents.6.7.4
45、.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 delivering 0 to 2 mL/min of reagentsolution against a back pressure of up to 40
46、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 Recorder, integrator or computer:Adevice compatible with detector output, capab
47、le 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 solution.6.7.6 Syringe filter, 0.45 m, for sample filtration prior toanalysis.
48、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, use onlyreagents of recognized analytical grade, and only water asspecifie
49、d 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 (H2SO4), 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.
