1、Designation: D6832 131Standard 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 D6832; the number immediately following the designation indic
2、ates 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.1NOTEEditorial corrections were made in October 2013.1.
3、 Scope1.1 This test method specifies a method for the 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
4、 (static) sampling.1.3 The sample dissolution procedure 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
5、 chromium in airfor which this procedure is applicable 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
6、processes are minimized to the extent possible by thesampling and sample preparation procedures employed.1.7 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.8 This standard does not purport to address all of thesafety concerns
7、, 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 Standards:2D1193 Specification for Reagent WaterD1356
8、Terminology Relating to Sampling and Analysis ofAtmospheresD3195 Practice for Rotameter CalibrationD4840 Guide for Sample Chain-of-Custody ProceduresE882 Guide for Accountability and Quality Control in theChemical Analysis LaboratoryE1370 Guide for Air Sampling Strategies for Worker andWorkplace Pro
9、tection2.2 ISO Standards:3ISO 648 Laboratory GlasswareOne-mark PipetsISO 1042 Laboratory GlasswareOne-mark VolumetricFlasksISO 3585 Glass Plant, Pipeline and FittingsProperties ofBorosilicate Glass 3.3ISO 7708 Air QualityParticle Size Definitions for Health-related SamplingISO 8655 Piston and/or Plu
10、nger-operated Volumetric Appa-ratus (6 Parts)3. Terminology3.1 For definitions of terms used in this standard testmethod, refer to Terminology D1356.4. Summary of Test Method4.1 A known volume of air is drawn through a filter tocollect particulate hexavalent chromium. The sampler is de-signed to col
11、lect the inhalable fraction of airborne particles (seeISO 7708).4.2 The filter and collected sample are subjected to adissolution procedure in order to extract hexavalent chromium.1This test method is under the jurisdiction of ASTM Committee D22 on AirQualityand is the direct responsibility of Subco
12、mmittee D22.04 on Workplace AirQuality.Current edition approved Oct. 1, 2013. Published October 2013. Originallyapproved in 2002. Last previous edition approved in 2008 as D6832 - 08. DOI:10.1520/D6832-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer S
13、ervice at serviceastm.org. For Annual Book of ASTMStandards 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.Copyright ASTM International,
14、 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1The 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 measure both soluble as well as totalhexavalent chro
15、mium, 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 measure totalhexavalent chromium without first isola
16、ting insoluble CrVI compounds,only the procedure for insoluble CrVI is required (this will dissolve bothsoluble and insoluble hexavalent chromium compounds).4.2.1 For dissolution of soluble hexavalent chromium, dis-tilled water with no heating is used to treat the sample.Alternatively, a weakly basi
17、c ammonium sulfate/ammoniumhydroxide buffer solution with no heating is used to extractsoluble forms of hexavalent chromium.4.2.2 For dissolution of insoluble hexavalent chromium, abasic carbonate buffer solution with heating by a hot plate isused for sample treatment. Alternatively, an ultrasonic b
18、ath isused instead of a hot plate.4.3 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.4.4 Following s
19、eparation, 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.4.5 The absorbance of the chromium-diphenylca
20、rbazonecomplex 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.4.6 The analysis results may be used for the assessment ofworkplace exposures to hexavale
21、nt chromium in air.5. Significance and Use5.1 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 provides a me
22、ans for exposure assessment to thishighly toxic species.Analytical results from this procedure canbe used for regulatory compliance purposes (2).6. Reactions6.1 Reduction of hexavalent chromium to trivalent speciescan occur in acidic environments, and also in the presence oforganic material or envir
23、onments 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 of air
24、(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).7. Apparatus7.1 Samplers, designed to collect the inhalable fraction ofairborne particles, for use when the exposure
25、 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 3Consider wh
26、ether 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 Appendix X1
27、 for guidance on handling of walldeposits within sampling cassettes.7.2 Filters, of a diameter suitable for use with the samplers(7.1), 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 analysis
28、 method.NOTE 4Typical filter diameters for personal sampling are 25 mm and37 mm.7.2.1 Filters should not react with Cr(VI). The following areacceptable:7.2.1.1 Polyvinyl chloride (PVC) membrane filters, 5mpore size or below.7.2.1.2 Polyvinyl fluoride (PVF) membrane filters, 5mpore size or below.7.2.
29、1.3 Polytetrafluorinated ethylene (PTFE) membranefilters, 5 m pore size or below.7.2.1.4 Glass fiber filters, binder-free.7.2.1.5 Quartz fiber filters.7.2.1.6 PVC/acrylic copolymer membrane filters, 5 m poresize or less.NOTE 5Several types of filters have been found to cause reduction ofhexavalent c
30、hromium (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 chromic acid
31、 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(VI) to re
32、act 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 membranefilt
33、ers have been found to be suitable for alkali treatment (3).7.3 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 possibility
34、 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.4The boldface numbers in parentheses refer to the list of references at the end ofthis test method.D6832 13127.4 Sampling pumps, with an
35、 adjustable flow 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 period
36、s for high-volume 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 set using either aprimary or secondary standard; if a secondary standard is used,it shall be calibrated using a primary st
37、andard (see D3195).NOTE 8A flow-stabilized pump may be required to maintain the flowrate within the specified limits.7.5 Flowmeter, portable, capable of measuring the selectedvolumetric flow rate to within 62 %, and calibrated against aprimary standard (that is, a flowmeter whose accuracy istraceabl
38、e to primary standards).7.6 Ancillary equipment:7.6.1 Flexible tubing, of a diameter suitable for making aleak-proof connection from the sampler to the sampling pump.7.6.2 Belts or harnesses, to which the sampling pump canbe conveniently fixed for personal sampling (except wheresampling pumps are sm
39、all enough to fit inside workerspockets).7.6.3 Flat-tipped forceps, plastic or plastic-tipped, for load-ing and unloading filters into or out of samplers.7.6.4 Filter transport cassettes, or similar, if required, inwhich to transport samples for laboratory analysis.7.6.5 Disposable gloves, for sampl
40、e handling and preven-tion of sample contamination.7.7 Analytical or laboratory apparatusOrdinary laboratory apparatus, and:7.7.1 Glassware, made of borosilicate glass 3.3 and com-plying with the requirements of ISO 3585.7.7.1.1 Beakers, of capacities between 50 mL and 2 L.7.7.1.2 Watch glasses, to
41、fit the beakers.7.7.1.3 One-mark pipets, complying with the requirementsof ISO 648.7.7.1.4 One-mark volumetric flasks, of capacities between10 mL and 1000 mL, complying with the requirements ofISO 1042.7.7.1.5 Piston-operated volumetric apparatus, complyingwith the requirements of ISO 8655. Pipettor
42、s, as an alternativeto one-mark pipets for the preparation of standard solutions,calibration solutions, and dilution of samples. Dispensors, fordispensing acids.7.7.2 Hot plate, thermostatically controlled, capable ofmaintaining a surface temperature of approximately 135C; forhot plate extraction of
43、 insoluble hexavalent chromium com-pounds.7.7.3 Sonicator, minimum power output 0.5 W/cm2, for usein the ultrasonic extraction of insoluble hexavalent chromiumcompounds.7.7.4 Ion chromatograph, having the following compo-nents:NOTE 9The following components should be comprised, to the extentpossible
44、, of inert materials.7.7.4.1 Pump, capable of delivering a constant flow in therange of 1 to 5 mL/min at a pressure of 15 to 150 MPa.7.7.4.2 Injection valve: A low dead-volume valve, (1 mL orless), nonmetallic, that will allow the loading of samplecontents into the eluant stream. Sample loops of up
45、to 1 mLvolume will provide enhanced detection limits.NOTE 10Either an autosampler or a manual injection system, or both,is (are) acceptable.7.7.4.3 Guard column: A column placed before the separa-tor column (7.7.4.4) to protect the separator column fromfouling by particles or strongly adsorbed organ
46、ic constituents.7.7.4.4 Separator column: A column packed with highcapacity pellicular anion exchange resin that is suitable forresolving hexavalent chromium from other metals and cations.7.7.4.5 Reagent delivery module: A device capable of de-livering 0 to 2 mL/min of reagent solution against a bac
47、kpressure of up to 40 kPa.7.7.4.6 Mixing tee and reaction coil: A device capable ofmixing two flowing streams with minimal band spreading.7.7.4.7 Detector: Alow-volume flow-through visible absor-bance detector with a nonmetallic flow path.7.7.4.8 Recorder, integrator or computer: Adevice compat-ible
48、 with detector output, capable of recording detector re-sponse as a function of time for the purpose of measuring peakheight or area.NOTE 11The use of an automated system is recommended.7.7.5 Eluant reservior: A container suitable for storingeluant solution.7.7.6 Syringe filter, 0.45 m, for sample f
49、iltration prior toanalysis. The filter material shall be chemically inert.7.7.7 Syringe, equipped with a male fitting and a capacity ofat least 1 mL; or auto sampler module with like specifications.8. Reagents8.1 For the analysis of hexavalent chromium, use onlyreagents of recognized analytical grade, and only water asspecified in (8.1.1).8.1.1 Water, complying with the requirements of ASTMType 1 water (as specified in Specification D1193: electricalconductivity less than 0.1 mS/m and resistivity greater than0.01 M-m at 25C).8.1.2 Sulfuric acid
