ASTM D6832-02

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D6832–02
Standard Test Method for
the Determination of Hexavalent Chromium in Workplace Air
by Ion Chromatography and Spectrophotometric
Measurement Using 1,5-diphenylcarbazide
This standard is issued under the fixed designation D 6832; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope E 882 Guide for Accountability and Quality Control in the
Chemical Analysis Laboratory
1.1 This test method specifies a method for the determina-
E 1370 Guide for Air Sampling Strategies for Worker and
tion of the time-weighted average mass concentration of
Workplace Protection
hexavalent chromium in workplace air.
2.2 ISO Standards:
1.2 Themethodisapplicabletothepersonalsamplingofthe
ISO 648 Laboratory Glassware— One-mark Pipets
inhalable fraction of airborne particles, as defined in ISO 7708,
ISO 1042 Laboratory Glassware— One-mark Volumetric
and to area (static) sampling.
Flasks
1.3 The sample dissolution procedure specifies separate
ISO 3585 Glass Plant, Pipeline and Fittings— Properties of
procedures for soluble and insoluble hexavalent chromium.
Borosilicate Glass 3.3
1.4 The method is applicable to the determination of masses
ISO 7708 Particle Size Definitions for Health-related Sam-
of 0.01 µg to 10 µg of hexavalent chromium per sample
pling
without dilution.
ISO 8655 Piston and/or Plunger-operated VolumetricAppa-
1.5 The concentration range for hexavalent chromium in air
ratus (6 Parts)
for which this procedure is applicable is approximately 0.1
3 3 3
µg/m to 100 µg/m , assuming 1 m of air sample. The range
3. Summary of Test Method
can be extended upwards by appropriate dilution.
3.1 A known volume of air is drawn through a filter to
1.6 Interconversion of trivalent and hexavalent chromium
collect particulate hexavalent chromium. The sampler is de-
species may occur during sampling and sample preparation,
signedtocollecttheinhalablefractionofairborneparticles(see
but these processes are minimized to the extent possible by the
ISO 7708).
sampling and sample preparation procedures employed.
3.2 The filter and collected sample are subjected to a
1.7 This standard does not purport to address all of the
dissolution procedure in order to extract hexavalent chromium.
safety concerns, if any, associated with its use. It is the
The sample dissolution procedure may consist of one (or both)
responsibility of the user of this standard to establish appro-
of two techniques: one for soluble and one for insoluble
priate safety and health practices and determine the applica-
hexavalent chromium.
bility of regulatory limitations prior to use.
NOTE 1—If it is desired to measure both soluble as well as total
2. Referenced Documents
hexavalent chromium, the soluble procedure is used first, and this is
followed by the procedure for insoluble hexavalent chromium com-
2.1 ASTM Standards:
pounds. Thus, total Cr[VI] is the sum of soluble and insoluble hexavalent
D 1193 Specification for Reagent Water
chromium compounds. On the other hand, if it is desired to measure total
D 1605 Terminology Related to Atmospheric Sampling
hexavalent chromium without first isolating insoluble Cr[VI] compounds,
D 4840 Guide for Sampling Chain-of-Custody Procedures
only the procedure for insoluble Cr[VI] is required (this will dissolve both
soluble and insoluble hexavalent chromium compounds).
This test method is under the jurisdiction of ASTM Committee D22 on 3.2.1 For dissolution of soluble hexavalent chromium, dis-
Sampling and Analysis of Atmospheres and is the direct responsibility of Subcom-
tilled water with no heating is used to treat the sample.
mittee D22.04 on Workplace Atmospheres.
Alternatively, a weakly basic ammonium sulfate/ammonium
Current edition approved October 10, 2002. Published December 2002.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6832–02
NOTE 3—Consider whether the sample is meant to constitute only that
hydroxide buffer solution with no heating is used to extract
material which is collected on filter material, or whether the sample
soluble forms of hexavalent chromium.
comprises all particulate that is captured within the sampler (that is, all
3.2.2 For dissolution of insoluble hexavalent chromium, a
material on the filter, backup pad (if applicable), and on the inside walls
weakly basic carbonate buffer solution with heating by a hot
of the sampler).
plate is used for sample treatment. Alternatively, an ultrasonic
6.2 Filters, of a diameter suitable for use with the samplers
bath is used instead of a hot plate.
(6.1), with a collection efficiency of not less than 99.5 % for
3.3 Aliquots of sample extracts are subjected to ion chro-
particles with a 0.3 µm diffusion diameter (ISO 7708), and
matography in order to separate extracted hexavalent chro-
compatible with the sample preparation and analysis method.
mium from trivalent chromium and other metal cations. An
ammonium sulfate/ammonium hydroxide eluent solution is
NOTE 4—Typical filter diameters for personal sampling are 25 mm and
used as the mobile phase.
37 mm.
3.4 Following separation, hexavalent chromium is reacted
6.2.1 FiltersshouldnotreactwithCr(VI).Thefollowingare
with an acidic solution of 1,5-diphenylcarbazide to form a
acceptable:
characteristic violet chromium-diphenylcarbazone complex.
6.2.1.1 Polyvinyl chloride (PVC) membrane filters,5µm
Post-column derivatization is used in order to react hexavalent
pore size or below.
chromium with 1,5-diphenylcarbazide.
6.2.1.2 Polyvinyl fluoride (PVF) membrane filters,5µm
3.5 The absorbance of the chromium-diphenylcarbazone
pore size or below.
complex is measured at 540 nm using visible spectrophotom-
6.2.1.3 Polytetrafluorinated ethylene (PTFE) membrane fil-
etry. Analytical results are obtained by plotting the measured
ters, 5 µm pore size or below.
absorbance as a function of concentration of the chromium-
6.2.1.4 Glass fiber filters, binder-free.
diphenylcarbazone complex.
6.2.1.5 Quartz fiber filters.
3.6 The analysis results may be used for the assessment of
6.2.1.6 PVC/acrylic copolymer membrane filters, 5 µm pore
workplace exposures to hexavalent chromium in air.
size or less.
4. Significance and Use
NOTE 5—Several types of filters have been found to cause reduction of
4.1 Airbornehexavalentchromiumiscarcinogenic (1), and hexavalent chromium (4). Mixed cellulose ester (MCE) filters may cause
significant reduction of hexavalent chromium, and are generally unsuit-
analytical methods for the measurement of this species in
able. Some PVC filters have been reported to cause hexavalent chromium
workplace aerosols are desired.Worker exposure to hexavalent
reduction; this should be investigated prior to choosing PVC filters.
chromium occurs primarily through inhalation (1), and this test
NOTE 6—Whensamplingchromicacidmist,thereisanadvantageifthe
method provides a means for exposure assessment to this
oxidizing potential of hexavalent chromium is lowered, for instance by
highly toxic species.Analytical results from this procedure can
impregnating the filter with alkali. For example, this can be accomplished
be used for regulatory compliance purposes (2).
by soaking the filter overnight in 1 M sodium hydroxide, and allowing it
to dry. This lessens the tendency of Cr(VI) to react with organic
5. Reactions
compoundsinthefiltermaterial,orreducingagentsanddustpresentinthe
sampled air, or both. Filter materials such as PVC and PTFE can be
5.1 Reduction of hexavalent chromium to trivalent species
unsuitable for alkali treatment since they tend to be hydrophobic and
can occur in acidic environments, and also in the presence of
therefore not easily wetted. PVF and vinyl/acrylic copolymer membrane
organic material or environments having high iron concentra-
filters have been found to be suitable for alkali treatment (3).
tions in air (3). Reduction of hexavalent chromium can also
6.3 Backup pads, if necessary for use in the particular
occur on filter media (4), and efforts should to taken to
sampler employed.
minimize this contribution to sample loss. Oxidation of triva-
lent chromium to hexavalent species can occur in strong base
NOTE 7—Cellulose backup pads should not be used for sampling of
and in the presence of air (5), so efforts should be taken to
chromicacidmist,sincedropletscanpenetratethefilterbycapillaryforce,
minimize these contributions to analytical bias. In plating mist resulting in the possibility of Cr(VI) reduction with the backup pad
material. Glass or quartz fiber backup pads could be used, or a mesh
samples and in some welding fume samples, interference from
comprised of material that is resistant to chromic acid.
iron may be problematic (2).
6.4 Sampling pumps, with an adjustable flow rate and
6. Apparatus
capable of maintaining the selected flow rate (between 1 and 5
6.1 Samplers, designed to collect the inhalable fraction of L/min for personal sampling pumps, and between 5 and 400
airborne particles, for use when the exposure limits of interest L/minforhigh-volumesamplingpumps)towithin 65 %ofthe
apply to the inhalable fraction of airborne particles (as defined nominalvaluethroughoutthesamplingperiod(upto8-10hfor
in ISO 7708). personal sampling, or shorter periods for high-volume sam-
pling). For personal sampling the pumps shall be capable of
NOTE 2—In general, personal samples for collection of the inhalable
being worn by the worker without impeding normal work
fraction of airborne particles do not exhibit the same size selective
activity. Sampling pump flow rates shall be calibrated using
characteristics if used for area (static) sampling.
either a primary or secondary standard; if a secondary standard
is used, it shall be calibrated using a primary standard.
NOTE 8—Aflow-stabilized pump may be required to maintain the flow
The boldface numbers in parentheses refer to the list of references at the end of
this test method. rate within the specified limits.
D6832–02
6.5 Flowmeter, portable, capable of measuring the selected 6.7.4.4 Separator column:
volumetric flow rate to within 62 %, and calibrated against a A column packed with high capacity pellicular anion ex-
primary standard (that is, a flowmeter whose accuracy is changeresinthatissuitableforresolvinghexavalentchromium
traceable to primary standards). from other metals and cations.
6.6 Ancillary equipment: 6.7.4.5 Reagent delivery module:
6.6.1 Flexible tubing, of a diameter suitable for making a A device capable of delivering 0 to 2 mL/min of reagent
leak-proof connection from the sampler to the sampling pump. solution against a back pressure of up to 40 kPa.
6.6.2 Belts or harnesses, to which the sampling pump can 6.7.4.6 Mixing tee and reaction coil:
be conveniently fixed for personal sampling (except where
A device capable of mixing two flowing streams with
sampling pumps are small enough to fit inside workers’ minimal band spreading.
pockets).
6.7.4.7 Detector:
6.6.3 Flat-tipped forceps, for loading and unloading filters
Alow-volumeflow-throughvisibleabsorbancedetectorwith
into or out of samplers.
a nonmetallic flow path.
6.6.4 Filter transport cassettes, or similar, if required, in
6.7.4.8 Recorder, integrator or computer:
which to transport samples for laboratory analysis.
Adevice compatible with detector output, capable of record-
6.6.5 Disposable gloves, for sample handling and preven-
ing detector response as a function of time for the purpose of
tion of sample contamination. measuring peak height or area.
6.7 Analytical or laboratory apparatus
NOTE 11—The use of an automated system is recommended.
Ordinary laboratory apparatus, and:
6.7.1 Glassware, made of borosilicate glass 3.3 and com- 6.7.5 Eluant reservior:
plying with the requirements of ISO 3585. A container suitable for storing eluant solution.
6.7.1.1 Beakers, of capacities between 50 mL and 2 L. 6.7.6 Syringe filter, 0.45 µm, for sample filtration prior to
6.7.1.2 Watch glasses, to fit the beakers. analysis. The filter material shall be chemically inert.
6.7.1.3 One-mark pipets, complying with the requirements
6.7.7 Syringe,equippedwithamalefittingandacapacityof
of ISO 648. at least 1 mL; or auto sampler module with like specifications.
6.7.1.4 One-mark volumetric flasks, of capacities between
10 mL and 1000 mL, complying with the requirements of ISO 7. Reagents
1042.
7.1 For the analysis of hexavalent chromium, use only
6.7.1.5 Piston-operated volumetric apparatus, complying
reagents of recognized analytical grade, and only water as
with the requirements of ISO 8655. Pipettors, as an alternative
specified in (7.1.1).
to one-mark pipets for the preparation of standard solutions,
7.1.1 Water, complying with the requirements of ASTM
calibration solutions, and dilution of samples. Dispensors, for
Type 1 water (as specified in Specification D 1193: electrical
dispensing acids.
conductivity less than 0.1 mS/m and resistivity greater than
6.7.2 Hot plate, thermostatically controlled, capable of
0.01 M-V-m at 25°C).
maintaining a surface temperature of approximately 135°C; for
7.1.2 Sulfuric acid (H SO ), concentrated, specific gravity
2 4
hot plate extraction of insoluble hexavalent chromium com-
~1.84 g/mL, ~98 % (m/m).
pounds.
7.1.3 Nitric acid (HNO ), concentrated, specific gravity
6.7.3 Sonicator, minimum power output 0.5 W/cm , for use
~1.42 g/mL, 69-71 % (m/m).
in the ultrasonic extraction of insoluble hexavalent chromium
7.1.4 Nitric acid wash solution (1 % HNO ):
compounds.
Dilute 10 mL of concentrated nitric acid (7.1.3) to 1 litre
6.7.4 Ion chromatograph, having the following compo-
with water (7.1.1).
nents:
7.1.5 Sodium carbonate (Na CO ), anhydrous, purity
2 3
greater than 99.9 % (m/m).
NOTE 9—Thefollowingcomponentsshouldbecomprised,totheextent
possible, of inert materials. 7.1.6 Sodium hydroxide (NaOH), pellets, purity greater than
99.5 % (m/m).
6.7.4.1 Pump, capable of delivering a constant flow in the
7.1.7 Ammonium sulfate ((NH ) SO ), purity greater than
4 2 4
range of 1 to 5 mL/min at a pressure of 15 to 150 MPa.
99.5 % (m/m).
6.7.4.2 Injection valve:
7.1.8 Ammonia (NH ), concentrated, specific gravity ~0.90
A low dead-volume valve, (1 mL or less), nonmet
...