1、Designation: D6832 08D6832 13Standard 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 designatio
2、n indicates 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
3、for the determination of the time-weighted average mass concentration of hexavalentchromium in workplace air samples.1.2 The method is applicable to the personal sampling of the inhalable fraction of airborne particles, as defined in ISO 7708,and to area (static) sampling.1.3 The sample dissolution
4、procedure specifies separate procedures for soluble and insoluble hexavalent chromium.1.4 The method is applicable to the determination of masses of 0.01 g to 10 g of hexavalent chromium per sample withoutdilution.1.5 The concentration range for hexavalent chromium in air for which this procedure is
5、 applicable is approximately 0.1 g/m3to 100 g/m3, assuming 1 m3 of air sample. The range can be extended upwards by appropriate dilution.1.6 Interconversion of trivalent and hexavalent chromium species may occur during sampling and sample preparation, but theseprocesses are minimized to the extent p
6、ossible by the sampling and sample preparation procedures employed.1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use.
7、It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD1356 Terminology Relating to Sampling and A
8、nalysis of AtmospheresD3195 Practice for Rotameter CalibrationD4840 Guide for Sample Chain-of-Custody ProceduresE882 Guide for Accountability and Quality Control in the Chemical Analysis LaboratoryE1370 Guide for Air Sampling Strategies for Worker and Workplace Protection2.2 ISO Standards:3ISO 648 L
9、aboratory GlasswareOne-mark PipetsISO 1042 Laboratory GlasswareOne-mark Volumetric FlasksISO 3585 Glass Plant, Pipeline and FittingsProperties of Borosilicate Glass 3.3ISO 7708 Particle Air QualityParticle Size Definitions for Health-related SamplingISO 8655 Piston and/or Plunger-operated Volumetric
10、 Apparatus (6 Parts)3. Terminology3.1 For definitions of terms used in this standard test method, refer to Terminology D1356.1 This test method is under the jurisdiction of ASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.04 on Workplace Air Quality.Current editi
11、on approved Aug. 1, 2008Oct. 1, 2013. Published September 2008October 2013. Originally approved in 2002. Last previous edition approved in 20022008as D6832 - 02.D6832 - 08. DOI: 10.1520/D6832-08.10.1520/D6832-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Cust
12、omer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not
13、 an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate
14、. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test Method4.1 A known volume of air is drawn through
15、a filter to collect particulate hexavalent chromium. The sampler is designed tocollect the inhalable fraction of airborne particles (see ISO 7708).4.2 The filter and collected sample are subjected to a dissolution procedure in order to extract hexavalent chromium.The sampledissolution procedure may
16、consist of one (or both) of two techniques: one for soluble and one for insoluble hexavalent chromium.NOTE 1If it is desired to measure both soluble as well as total hexavalent chromium, the soluble procedure is used first, and this is followed by theprocedure for insoluble hexavalent chromium compo
17、unds. Thus, total CrVI is the sum of soluble and insoluble hexavalent chromium compounds. Onthe other hand, if it is desired to measure total hexavalent chromium without first isolating insoluble CrVI compounds, only the procedure for insolubleCrVI is required (this will dissolve both soluble and in
18、soluble hexavalent chromium compounds).4.2.1 For dissolution of soluble hexavalent chromium, distilled water with no heating is used to treat the sample. Alternatively,a weakly basic ammonium sulfate/ammonium hydroxide buffer solution with no heating is used to extract soluble forms ofhexavalent chr
19、omium.4.2.2 For dissolution of insoluble hexavalent chromium, a weakly basic carbonate buffer solution with heating by a hot plateis used for sample treatment. Alternatively, an ultrasonic bath is used instead of a hot plate.4.3 Aliquots of sample extracts are subjected to ion chromatography in orde
20、r to separate extracted hexavalent chromium fromtrivalent chromium and other metal cations. An ammonium sulfate/ammonium hydroxide eluent solution is used as the mobilephase.4.4 Following separation, hexavalent chromium is reacted with an acidic solution of 1,5-diphenylcarbazide to form acharacteris
21、tic 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-diphenylcarbazone complex is measured at 540 nm using visible spectrophotometry.Analytical results are obtained by plot
22、ting the measured absorbance as a function of concentration of the chromium-diphenylcarbazone complex.4.6 The analysis results may be used for the assessment of workplace exposures to hexavalent chromium in air.5. Significance and Use5.1 Airborne hexavalent chromium is carcinogenic (1),4 and analyti
23、cal methods for the measurement of this species inworkplace aerosols are desired. Worker exposure to hexavalent chromium occurs primarily through inhalation (1), and this testmethod provides a means for exposure assessment to this highly toxic species. Analytical results from this procedure can be u
24、sedfor regulatory compliance purposes (2).6. Reactions6.1 Reduction of hexavalent chromium to trivalent species can occur in acidic environments, and also in the presence of organicmaterial or environments having high iron concentrations in air (3). Reduction of hexavalent chromium can also occur on
25、 filtermedia (4), and efforts should to taken to minimize this contribution to sample loss. Oxidation of trivalent chromium to hexavalentspecies can occur in strong base and in the presence of air (5), so efforts should be taken to minimize these contributions toanalytical bias. In plating mist samp
26、les and in some welding fume samples, interference from iron may be problematic(3).7. Apparatus7.1 Samplers, designed to collect the inhalable fraction of airborne particles, for use when the exposure limits of interest applyto the inhalable fraction of airborne particles (as defined in ISO 7708).NO
27、TE 2In general, personal samples for collection of the inhalable fraction of airborne particles do not exhibit the same size selective characteristicsif used for area (static) sampling.NOTE 3Consider whether the sample is meant to constitute only that material which is collected on filter material,
28、or whether the sample comprisesall particulate that is captured within the sampler (that is, all material on the filter, backup pad (if applicable), and on the inside walls of the sampler).See Appendix X1 for guidance on handling of wall deposits within sampling cassettes.7.2 Filters, of a diameter
29、suitable for use with the samplers (6.17.1), with a collection efficiency of not less than 99.5 % forparticles with a 0.3 m diffusion diameter (ISO 7708), and compatible with the sample preparation and analysis method.NOTE 4Typical filter diameters for personal sampling are 25 mm and 37 mm.7.2.1 Fil
30、ters should not react with Cr(VI). The following are acceptable:7.2.1.1 Polyvinyl chloride (PVC) membrane filters, 5 m pore size or below.7.2.1.2 Polyvinyl fluoride (PVF) membrane filters, 5 m pore size or below.7.2.1.3 Polytetrafluorinated ethylene (PTFE) membrane filters, 5 m pore size or below.4
31、The boldface numbers in parentheses refer to the list of references at the end of this test method.D6832 1327.2.1.4 Glass fiber filters, binder-free.7.2.1.5 Quartz fiber filters.7.2.1.6 PVC/acrylic copolymer membrane filters, 5 m pore size or less.NOTE 5Several types of filters have been found to ca
32、use reduction of hexavalent chromium (4). Mixed cellulose ester (MCE) filters may causesignificant reduction of hexavalent chromium, and are generally unsuitable. Some PVC filters have been reported to cause hexavalent chromiumreduction; this should be investigated prior to choosing PVC filters.NOTE
33、 6When sampling chromic acid mist, there is an advantage if the oxidizing potential of hexavalent chromium is lowered, for instance byimpregnating the filter with alkali. For example, this can be accomplished by soaking the filter overnight in 1 M sodium hydroxide, and allowing it todry. This lessen
34、s the tendency of Cr(VI) to react with organic compounds in the filter material, or reducing agents and dust present in the sampled air,or both. Filter materials such as PVC and PTFE can be unsuitable for alkali treatment since they tend to be hydrophobic and therefore not easily wetted.PVF and viny
35、l/acrylic copolymer membrane filters have been found to be suitable for alkali treatment (3).7.3 Backup pads, if necessary for use in the particular sampler employed.NOTE 7Cellulose backup pads should not be used for sampling of chromic acid mist, since droplets can penetrate the filter by capillary
36、 force, resultingin the possibility of Cr(VI) reduction with the backup pad material. Glass or quartz fiber backup pads could be used, or a mesh comprised of materialthat is resistant to chromic acid.7.4 Sampling pumps, with an adjustable flow rate and capable of maintaining the selected flow rate (
37、between 1 and 5 L/min forpersonal sampling pumps, and between 5 and 400 L/min for high-volume sampling pumps) to within 65 % of the nominal valuethroughout the sampling period (up to 8-10 h for personal sampling, or shorter periods for high-volume sampling). For personalsampling the pumps shall be c
38、apable of being worn by the worker without impeding normal work activity. Sampling pump flowrates shall be calibratedset using either a primary or secondary standard; if a secondary standard is used, it shall be calibrated usinga primary standard (see D3195).NOTE 8A flow-stabilized pump may be requi
39、red to maintain the flow rate within the specified limits.7.5 Flowmeter, portable, capable of measuring the selected volumetric flow rate to within 62 %, and calibrated against aprimary standard (that is, a flowmeter whose accuracy is traceable to primary standards).7.6 Ancillary equipment:7.6.1 Fle
40、xible tubing, of a diameter suitable for making a leak-proof connection from the sampler to the sampling pump.7.6.2 Belts or harnesses, to which the sampling pump can be conveniently fixed for personal sampling (except where samplingpumps are small enough to fit inside workers pockets).7.6.3 Flat-ti
41、pped forceps, plastic or plastic-tipped, for loading and unloading filters into or out of samplers.7.6.4 Filter transport cassettes, or similar, if required, in which to transport samples for laboratory analysis.7.6.5 Disposable gloves, for sample handling and prevention of sample contamination.7.7
42、Analytical or laboratory apparatusOrdinary laboratory apparatus, and:7.7.1 Glassware, made of borosilicate glass 3.3 and complying 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 fit the beakers.7.7.1.3 One-mark pipets, complying with
43、the requirements of ISO 648.7.7.1.4 One-mark volumetric flasks, of capacities between 10 mL and 1000 mL, complying with the requirements of ISO 1042.7.7.1.5 Piston-operated volumetric apparatus, complying with the requirements of ISO 8655. Pipettors, as an alternative toone-mark pipets for the prepa
44、ration of standard solutions, calibration solutions, and dilution of samples. Dispensors, for dispensingacids.7.7.2 Hot plate, thermostatically controlled, capable of maintaining a surface temperature of approximately 135C; for hot plateextraction of insoluble hexavalent chromium compounds.7.7.3 Son
45、icator, minimum power output 0.5 W/cm2, for use in the ultrasonic extraction of insoluble hexavalent chromiumcompounds.7.7.4 Ion chromatograph, having the following components:NOTE 9The following components should be comprised, to the extent possible, of inert materials.7.7.4.1 Pump, capable of deli
46、vering a constant flow in the range 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 or less), nonmetallic, that will allow the loading of sample contentsinto the eluant stream. Sample loops of up to 1 mL volume will provide enhanced detection l
47、imits.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 separator column (6.7.4.47.7.4.4) to protect the separator column fromfouling by particles or strongly adsorbed organic constituents.7.7.4.4 Separator column
48、: A column packed with high capacity pellicular anion exchange resin that is suitable for resolvinghexavalent chromium from other metals and cations.D6832 1337.7.4.5 Reagent delivery module: A device capable of delivering 0 to 2 mL/min of reagent solution against a back pressure ofup to 40 kPa.7.7.4
49、.6 Mixing tee and reaction coil: A device capable of mixing two flowing streams with minimal band spreading.7.7.4.7 Detector: A low-volume flow-through visible absorbance detector with a nonmetallic flow path.7.7.4.8 Recorder, integrator or computer: A device compatible with detector output, capable of recording detector response asa function of time for the purpose of measuring peak height or area.NOTE 11The use of an automated system is recommended.7.7.5 Eluant reservior: A container suitable for storing eluant solution.7.7.6 Syringe filter, 0.45
