ASTM D6832-13(2018)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6832 − 13 (Reapproved 2018)
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 D6832; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.1 This test method specifies a method for the determina-
tion of the time-weighted average mass concentration of
2. Referenced Documents
hexavalent chromium in workplace air samples.
2.1 ASTM Standards:
1.2 This test method is applicable to the personal sampling
D1193Specification for Reagent Water
of the inhalable fraction of airborne particles, as defined in
D1356Terminology Relating to Sampling and Analysis of
ISO7708, and to area (static) sampling.
Atmospheres
1.3 The sample dissolution procedure specifies separate
D3195Practice for Rotameter Calibration
procedures for soluble and insoluble hexavalent chromium.
D4840Guide for Sample Chain-of-Custody Procedures
E882Guide for Accountability and Quality Control in the
1.4 This test method is applicable to the determination of
Chemical Analysis Laboratory
massesof0.01µgto10µgofhexavalentchromiumpersample
E1370Guide for Air Sampling Strategies for Worker and
without dilution.
Workplace Protection
1.5 The concentration range for hexavalent chromium in air
2.2 ISO Standards:
for which this procedure is applicable is approximately 0.1
3 3 3 ISO648Laboratory Glassware—One-mark Pipets
µg/m to 100 µg/m , assuming 1 m of air sample. The range
ISO 1042 Laboratory Glassware—One-mark Volumetric
can be extended upwards by appropriate dilution.
Flasks
1.6 Interconversion of trivalent and hexavalent chromium
ISO3585Glass Plant, Pipeline and Fittings—Properties of
species may occur during sampling and sample preparation,
Borosilicate Glass 3.3
but these processes are minimized to the extent possible by the
ISO7708Air Quality—Particle Size Definitions for Health-
sampling and sample preparation procedures employed.
related Sampling
1.7 The values stated in SI units are to be regarded as ISO8655Piston and/or Plunger-operated Volumetric Appa-
ratus (6 Parts)
standard. No other units of measurement are included in this
standard.
3. Terminology
1.8 This standard does not purport to address all of the
3.1 Fordefinitionsoftermsusedinthistestmethod,referto
safety concerns, if any, associated with its use. It is the
Terminology D1356.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4. Summary of Test Method
mine the applicability of regulatory limitations prior to use.
1.9 This international standard was developed in accor-
4.1 A known volume of air is drawn through a filter to
dance with internationally recognized principles on standard-
collect particulate hexavalent chromium. The sampler is de-
ization established in the Decision on Principles for the
signedtocollecttheinhalablefractionofairborneparticles(see
Development of International Standards, Guides and Recom-
ISO7708).
1 2
This test method is under the jurisdiction of ASTM Committee D22 on Air For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Quality and is the direct responsibility of Subcommittee D22.04 on WorkplaceAir contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Quality. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Dec. 1, 2018. Published December 2018. Originally the ASTM website.
ɛ1 3
approved in 2002. Last previous edition approved in 2013 as D6832–13 . DOI: Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/D6832-13R18. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6832 − 13 (2018)
4.2 The filter and collected sample are subjected to a occur on filter media (6), and efforts should to taken to
dissolutionprocedureinordertoextracthexavalentchromium. minimize this contribution to sample loss. Oxidation of triva-
The sample dissolution procedure may consist of one (or both) lent chromium to hexavalent species can occur in strong base
of two techniques: one for soluble and one for insoluble and in the presence of air (7), so efforts should be taken to
hexavalent chromium. minimize these contributions to analytical bias. In plating mist
samples and in some welding fume samples, interference from
NOTE 1—If it is desired to measure both soluble as well as total
iron may be problematic (5).
hexavalent chromium, the soluble procedure is used first, and this is
followed by the procedure for insoluble hexavalent chromium com-
pounds. Thus, total Cr[VI] is the sum of soluble and insoluble hexavalent
7. Apparatus
chromium compounds. On the other hand, if it is desired to measure total
7.1 Samplers, designed to collect the inhalable fraction of
hexavalent chromium without first isolating insoluble Cr[VI] compounds,
onlytheprocedureforinsolubleCr[VI]isrequired(thiswilldissolveboth airborne particles, for use when the exposure limits of interest
soluble and insoluble hexavalent chromium compounds).
apply to the inhalable fraction of airborne particles (as defined
in ISO7708).
4.2.1 For dissolution of soluble hexavalent chromium, dis-
tilled water with no heating is used to treat the sample.
NOTE 2—In general, personal samples for collection of the inhalable
Alternatively, a weakly basic ammonium sulfate/ammonium
fraction of airborne particles do not exhibit the same size selective
hydroxide buffer solution with no heating is used to extract characteristics if used for area (static) sampling.
NOTE 3—Consider whether the sample is meant to constitute only that
soluble forms of hexavalent chromium.
material which is collected on filter material, or whether the sample
4.2.2 For dissolution of insoluble hexavalent chromium, a
comprises all particulate that is captured within the sampler (that is, all
basic carbonate buffer solution with heating by a hot plate is
material on the filter, backup pad (if applicable), and on the inside walls
used for sample treatment. Alternatively, an ultrasonic bath is
of the sampler). See Appendix X1 for guidance on handling of wall
used instead of a hot plate. deposits within sampling cassettes.
7.2 Filters, of a diameter suitable for use with the samplers
4.3 Aliquots of sample extracts are subjected to ion chro-
matography in order to separate extracted hexavalent chro- (7.1), with a collection efficiency of not less than 99.5% for
particles with a 0.3-µm diffusion diameter (ISO7708), and
mium from trivalent chromium and other metal cations. An
compatible with the sample preparation and analysis method.
ammonium sulfate/ammonium hydroxide eluent solution is
used as the mobile phase.
NOTE 4—Typical filter diameters for personal sampling are 25 mm and
37 mm.
4.4 Following separation, hexavalent chromium is reacted
with an acidic solution of 1,5-diphenylcarbazide to form a
7.2.1 FiltersshouldnotreactwithCr(VI).Thefollowingare
characteristic violet chromium-diphenylcarbazone complex.
acceptable:
Post-column derivatization is used in order to react hexavalent
7.2.1.1 Polyvinyl Chloride (PVC) Membrane Filters, 5-µm
chromium with 1,5-diphenylcarbazide.
pore size or below.
7.2.1.2 Polyvinyl Fluoride (PVF) Membrane Filters, 5-µm
4.5 The absorbance of the chromium-diphenylcarbazone
pore size or below.
complex is measured at 540 nm using visible spectrophotom-
7.2.1.3 Polytetrafluorinated Ethylene (PTFE) Membrane
etry. Analytical results are obtained by plotting the measured
Filters, 5-µm pore size or below.
absorbance as a function of concentration of the chromium-
7.2.1.4 Glass Fiber Filters, binder-free.
diphenylcarbazone complex.
7.2.1.5 Quartz Fiber Filters.
4.6 The analysis results may be used for the assessment of
7.2.1.6 PVC/Acrylic Copolymer Membrane Filters, 5-µm
workplace exposures to hexavalent chromium in air.
pore size or less.
5. Significance and Use
NOTE 5—Several types of filters have been found to cause reduction of
4 hexavalent chromium (6). Mixed cellulose ester (MCE) filters may cause
5.1 Airborne hexavalent chromium is carcinogenic (1-3),
significant reduction of hexavalent chromium, and are generally unsuit-
and analytical methods for the measurement of this species in
able. Some PVC filters have been reported to cause hexavalent chromium
workplaceaerosolsaredesired.Workerexposuretohexavalent
reduction; this should be investigated prior to choosing PVC filters.
chromium occurs primarily through inhalation (1-3), and this NOTE6—Whensamplingchromicacidmist,thereisanadvantageifthe
oxidizing potential of hexavalent chromium is lowered, for instance by
test method provides a means for exposure assessment to this
impregnating the filter with alkali. For example, this can be accomplished
highlytoxicspecies.Analyticalresultsfromthisprocedurecan
by soaking the filter overnight in 1 M sodium hydroxide, and allowing it
be used for regulatory compliance purposes (4).
to dry. This lessens the tendency of Cr(VI) to react with organic
compoundsinthefiltermaterial,orreducingagentsanddustpresentinthe
6. Reactions
sampled air, or both. Filter materials such as PVC and PTFE can be
unsuitable for alkali treatment since they tend to be hydrophobic and
6.1 Reduction of hexavalent chromium to trivalent species
therefore not easily wetted. PVF and vinyl/acrylic copolymer membrane
can occur in acidic environments, and also in the presence of
filters have been found to be suitable for alkali treatment (5).
organic material or environments having high iron concentra-
7.3 Backup Pads, if necessary for use in the particular
tions in air (5). Reduction of hexavalent chromium can also
sampler employed.
NOTE 7—Cellulose backup pads should not be used for sampling of
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof chromicacidmist,sincedropletscanpenetratethefilterbycapillaryforce,
this test method. resulting in the possibility of Cr(VI) reduction with the backup pad
D6832 − 13 (2018)
material. Glass or quartz fiber backup pads could be used, or a mesh
7.7.4 Ion Chromatograph, having the following compo-
comprised of material that is resistant to chromic acid.
nents:
7.4 Sampling Pumps, with an adjustable flow rate and
NOTE9—Thefollowingcomponentsshouldbecomprised,totheextent
capable of maintaining the selected flow rate (between 1 and 5
possible, of inert materials.
L/min for personal sampling pumps, and between 5 and 400
7.7.4.1 Pump, capable of delivering a constant flow in the
L/minforhigh-volumesamplingpumps)towithin 65%ofthe
range of 1 to 5 mL/min at a pressure of 15 to 150 MPa.
nominal value throughout the sampling period (up to 8–10 h
7.7.4.2 InjectionValve—Alowdead-volumevalve,(1mLor
for personal sampling, or shorter periods for high-volume
less), nonmetallic, that will allow the loading of sample
sampling). For personal sampling the pumps shall be capable
contents into the eluant stream. Sample loops of up to 1 mL
of being worn by the worker without impeding normal work
volume will provide enhanced detection limits.
activity. Sampling pump flow rates shall be set using either a
NOTE 10—Either an autosampler or a manual injection system, or both,
primaryorsecondarystandard;ifasecondarystandardisused,
is (are) acceptable.
it shall be calibrated using a primary standard (see Practice
7.7.4.3 Guard Column—A column placed before the sepa-
D3195).
rator column (7.7.4.4) to protect the separator column from
NOTE 8—Aflow-stabilized pump may be required to maintain the flow
fouling by particles or strongly adsorbed organic constituents.
rate within the specified limits.
7.7.4.4 Separator Column—A column packed with high
7.5 Flowmeter, Portable, capable of measuring the selected
capacity pellicular anion exchange resin that is suitable for
volumetric flow rate to within 62%, and calibrated against a
resolving hexavalent chromium from other metals and cations.
primary standard (that is, a flowmeter whose accuracy is
7.7.4.5 Reagent Delivery Module—A device capable of
traceable to primary standards).
delivering 0 to 2 mL/min of reagent solution against a back
pressure of up to 40 kPa.
7.6 Ancillary Equipment:
7.7.4.6 Mixing Tee and Reaction Coil—Adevice capable of
7.6.1 Flexible Tubing, of a diameter suitable for making a
mixing two flowing streams with minimal band spreading.
leak-proof connection from the sampler to the sampling pump.
7.7.4.7 Detector—A low-volume flow-through visible ab-
7.6.2 Belts or Harnesses, to which the sampling pump can
sorbance detector with a nonmetallic flow path.
be conveniently fixed for personal sampling (except where
7.7.4.8 Recorder, Integrator, or Computer—A device com-
sampling pumps are small enough to fit inside workers’
patible with detector output, capable of recording detector
pockets).
response as a function of time for the purpose of measuring
7.6.3 Flat-Tipped Forceps, plastic or plastic-tipped, for
peak height or area.
loading and unloading filters into or out of samplers.
NOTE 11—The use of an automated system is recommended.
7.6.4 Filter Transport Cassettes, or similar, if required, in
which to transport samples for laboratory analysis.
7.7.5 Eluant Reservior—A container suitable for storing
7.6.5 Disposable Gloves, for sample handling and preven-
eluant solution.
tion of sample contamination.
7.7.6 Syringe Filter, 0.45 µm, for sample filtration prior to
analysis. The filter material shall be chemically inert.
7.7 Analytical or Laboratory Apparatus—Ordinary labora-
7.7.7 Syringe,equippedwithamalefittingandacapacityof
tory apparatus, and:
at least 1 mL; or auto sampler module with like specifications.
7.7.1 Glassware, made of borosilicate glass 3.3 and com-
plying with the requirements of ISO3585.
8. Reagents
7.7.1.1 Beakers, of capacities between 50 mL and 2 L.
8.1 For the analysis of hexavalent chromium, use only
7.7.1.2 Watch Glasses, to fit the beakers.
reagents of recognized analytical grade, and only water as
7.7.1.3 One-Mark Pipets, complying with the requirements
specified in (8.1.1).
of ISO648.
8.1.1 Water, complying with the requirements of ASTM
7.7.1.4 One-Mark Volumetric Flasks, of capacities between
Type 1 water (as specified in Specification D1193: electrical
10 mL and 1000 mL, complying with the requirements of
conductivity less than 0.1 mS/m and resistivity greater than
ISO1042.
0.01 M-Ω-m at 25°C).
7.7.1.5 Piston-Operated Volumetric Apparatus, complying
8.1.2 Sulfuric acid (H SO ), concentrated, specific gravity
2 4
with the requirements of ISO8655. Pipettors, as an alternative
~1.84 g/mL, ~98% (m/m).
to one-mark pipets for the preparation of standard solutions,
8.1.3 Nitric acid (HNO ), concentrated, specific gravity
calibration solutions, and dilution of samples. Dispensors, for
~1.42 g/mL, 69-71% (m/m).
dispensing acids.
8.1.4 Nitric acid wash solution (1 % HNO )—Dilute 10 mL
7.7.2 Hot Plate, thermostatically controlled, capable of
of concentrated nitric acid (8.1.3) to 1 litre with water (8.1.1).
maintainingasurfacetemperatureofapproximately135°C;for
8.1.5 Sodium carbonate (Na CO ), anhydrous, purity
2 3
hot plate extraction of insoluble hexavalent chromium com-
greater than 99.9% (m/m).
pounds.
8.1.6 Sodium hydroxide (NaOH),pellets,puritygreaterthan
7.7.3 Sonicator, minimum power output 0.5 W/cm , for use 99.5% (m/m).
in the ultrasonic extraction of insoluble hexavalent chromium 8.1.7 Ammonium sulfate ((NH ) SO ), purity greater than
4 2 4
compounds. 99.5% (m/m).
D6832 − 13 (2018)
8.1.8 Ammonia (NH ), concentrated, specific gravity ~0.90 then cooled in a dessicator) in water (8.1.1). Dilute with water
g/mL, ~29% (m⁄m). (8.1.1) to 100 mL in a one-mark volumetric flask, stopper and
8.1.9 1,5-diphenylcarbazide (C H NHNHCONHNHC H ), mix thoroughly.
6 5 6 5
purity greater than 98% (m/m).
NOTE 14—Potassium chromate (K CrO ) can be used as an alternative
2 4
8.1.10 Methanol (CH OH), HPLC grade.
to potassium dichromate for the preparation of hexavalent chromium
8.1.11 Potassium dichromate (K Cr O ),puritygreaterthan
standard solutions.
2 2 7
99.9% (m/m).
8.1.15.2 Hexavalent Chromium Working Standard Solution
8.1.12 Extraction solutions.
(1000 µg Cr/l)—Pipet 1.00 mLof the chromium stock solution
(8.1.15.1)intoa1-litreone-markvolumetricflaskanddiluteto
NOTE 12—Extraction solutions other than those specified may be used,
ifdesired,providedthatitcanbedemonstratedthattheperformanceofthe
volume with water (8.1.1). Stopper and mix thoroughly.
measuring procedure is not impaired.
Prepare this solution fresh monthly.
8.1.12.1 Extraction solution for insoluble Cr(VI) 8.1.15.3 Hexavalent Chromium Calibration Solutions—
compounds, 2% (m/v) sodium hydroxide/3% (m/v) sodium Prepare a minimum of five calibration solutions in the concen-
carbonate: Dissolve 20 g of sodium hydroxide pellets (8.1.6) tration range of 0.02 to 5 µg/Lby diluting appropriate pipetted
and 30 g of sodium carbonate (8.1.5) in 250 mL of water volumes of the 1000 µg/L standard solution (8.1.15.2)inthe
(8.1.1), swirl to mix, and allow to cool. Quantitatively transfer appropriate extraction solution (8.1.12). Prepare these solu-
the solution to a one litre volumetric flask, dilute to the mark tions fresh daily.
with water (8.1.1), stopper and mix thoroughly. 8.1.16 1,5-Diphenylcarbazide Reagent Solution—Dissolve
8.1.12.2 Extraction solutions for soluble Cr(VI) 0.125 g of 1,5-diphenylcarbazide (8.1.9) in 25 mLof methanol
compounds, either of the following: (8.1.10).Addabout100mLofwater(8.1.1)containing5.6mL
(1) Water (8.1.1), or of concentrated sulfuric acid (8.1.2). Dilute with water (8.1.1)
(2) Extraction buffer, ammonium sulfate/ammonium hy- to 250 mL in a one-mark volumetric flask, stopper and mix
droxide buffer solution (0.05 M (NH ) SO /0.05 M NH OH, thoroughly. Prepare this solution fresh daily.
4 2 4 4
pH ~8): Dissolve 6.6 g of ammonium sulfate ((NH ) SO )
4 2 4
NOTE15—Othersuitablesolvents,suchasacetone,maybeusedforthe
(8.1.7)inabout500mLofwater.Add3.25mLofconcentrated
preparation of the 1,5-diphenylcarbazide reagent solution (if desired).
ammoniumhydroxide(NH OH)(8.1.8).Mixwellanddiluteto
1 litre with water (8.1.1) in a one-mark volumetric flask.
9. Sampling
Stopper and mix thoroughly.
NOTE 16—For information on strategies for the sampling of workplace
atmospheres, consult Guide E1370.
NOTE13—Thisextractionbufferwilldissolvewater-solubleCr(VI),for
example, potassium chromate, and it may dissolve Cr(VI) compounds 9.1 Sampling Procedure:
which are not water-soluble, for example, strontium chromate. However,
9.1.1 Selection and Use of Samplers:
this buffer will not dissolve insoluble Cr(VI) compounds such as lead
9.1.1.1 Select a sampler designed for collection of the
chromate and barium chromate.The use of this extraction buffer serves to
inhalablefractionofairborneparticles,asdefinedinISO7708.
stabilizechromiumspeciesinsolution(forexample,trivalentandhexava-
lent)andtherebyreducesinterconversionratesoftrivalentandhexavalent
NOTE 17—If possible, samplers selected should be manufactured from
chromium valence states.
conducting material, since samplers comprised of non-conducting mate-
rial have electrostatic properties that can adversely influence representa-
8.1.13 Eluant Solutions:
tive sampling.
8.1.13.1 Eluant concentrate, 2.0 M ammonium sulfate,
9.1.1.2 Use the samplers at their designed flow rate (be-
(NH ) SO /1 M ammonium hydroxide, NH OH: Dissolve 264
4 2 4 4
tween 1 and 5 L/min), and in accordance with the manufac-
g of ammonium sulfate ((NH ) SO)(8.1.7) in about 500 mL
4 2 4
turer’sinstructions,sothattheycollecttheinhalablefractionof
of water. Add 65 mL of concentrated ammonium hydroxide
airborne particles.
(NH OH) (8.1.8). Mix well and dilute to 1 litre with water
9.1.2 Sampling Period:
(8.1.1) in a one-mark volumetric flask. Stopper and mix
9.1.2.1 Select a sampling period long enough to ensure that
thoroughly.
the amount of hexavalent chromium collected is adequate to
8.1.13.2 Eluant solution, 0.20 M ammonium sulfate,
enable hexavalent chromium in air concentrations to be deter-
(NH ) SO /0.1 M ammonium hydroxide, NH OH: Add 100
4 2 4 4
mined at the required level (see Guide E1370). Ideally, the
mL of eluant concentrate (8.1.13.1) to a 1-litre one-mark
sampling period should be for the entire workday.
volumetric flask and dilute to volume with water (8.1.1).
9.1.2.2 In calculating the minimum sampling time required,
Stopper and mix thoroughly.
it is necessary to consider the selected flow rate and the lower
8.1.14 pH Indicator papers, suitable for measuring the pH
limit of the recommended analytical working range of this test
ofsamplesolutions(pH8.0 60.5)andthepHofeffluentfrom
method.
the spectrophotometric detector (pH 2.0 or lower).
9.1.2.3 The sampling time shall not be so long as to risk
8.1.15 Hexavalent Chromium Standard Solutions:
overloading of the filter with particulate material. This is a
8.1.15.1 Hexavalent Chromium Stock Standard Solution
concern when high concentrations of hexavalent chromium in
(~1000 µg Cr/l)—Use a commercially available hexavalent
air are anticipated.
chromium standard solution with a certified concentration.
Observe the manufacturer’s expiration date or recommended
NOTE18—Iffilteroverloadingisanobservedorsuspectedproblemand
shelflife.Alternatively,dissolve0.2828gofpotassiumdichro-
it is desired to sample for the entire workday, it may be necessary to
mate (K Cr O ) (which has been dried at 105°C for1hand collect consecutive samples.
2 2 7
D6832 − 13 (2018)
9.2 Preparation of Sampling Equipment: used for sample collection. Subject these blank filters to
exactly the same handling procedures as the samples, but draw
9.2.1 Perform the following in an area where contamination
no air through them.
from hexavalent chromium is known to be at a minimum:
9.2.1.1 Clean the samplers before use by soaking them in
9.4 Transportation:
detergent solution, rinsing them thoroughly with water, and
9.4.1 For samplers having an internal filter cassette, remove
then drying them.
the filter cassette from each sampler and place within a
9.2.1.2 Load the filters into clean, dry samplers. Handle the
transport cover.
filters only with clean flat-tipped forceps and gloved hands.
NOTE 20—Transport covers are normally supplied by the manufacturer
Seal each loaded filter with tape or shrink-wrap in order to
secure the individual sections of the sampler. Cap the inlet and
9.4.2 For samplers of the disposable cassette type, transport
outlet of each sampler with a cover or plug to protect the filter
samples in the samplers from which they were collected.
and interior of the sampler from contamination.
NOTE 21—Samples may be placed in an ice cooler so that they are kept
refrigerated during transport.
NOTE 19—Samplers that are pre-loaded with filters are available
commercially from a number of vendors.
9.4.3 Samples shall be transported to the laboratory for
9.2.1.3 Remove the protective cover or plugs from a loaded
analysis in such a manner to prevent contamination and
sampler. Connect the sampling pump to the loaded sampler
damagetothesamplesintransit.Samplesshallbeindividually
using flexible tubing, and ensure that there are no leaks. Turn
and unambiguously labeled to ensure proper handling.
on the pump, and allow for an appropriate warm-up period (if
9.4.4 Avoid exposing filter samples to plasticizers that may
necessary).Settheselectedflowratewithanaccuracyof 65%
cause reduction of Cr(VI).
using the calibrated flowmeter. Finally, turn off the pump and
9.4.5 Follow sampling chain of custody procedures in
reseal the sampler.
accordance with Guide D4840 to ensure sample traceability.
Ensurethatthedocumentationthataccompaniesthesamplesis
9.3 Collection of Samples:
suitable for a “chain of custody” to be established.
9.3.1 For personal monitoring, fix the sampler to the cloth-
ing of the worker, and place within the workers breathing zone
10. Preparation of Apparatus
(see Terminology D1356). Attach the sampling pump to the
worker as appropriate, to minimize inconvenience. For fixed
10.1 Cleaning of Glassware—Perform all of the following
location sampling, select a suitable desired sampling site.
while wearing gloves.
9.3.2 When ready to initiate sampling, remove the cover or
10.1.1 Before use, clean all glassware to remove any re-
plug from the inlet of the sampler and turn on the pump to
sidual grease or chemicals by first soaking in laboratory
begin sampling. Record the time and initial pump flow rate.
detergent solution and then rinsing thoroughly with water.
9.3.3 Since it is possible for filters to become clogged,
10.1.2 After initial cleaning with detergent and water, clean
monitor the performance of the sampler frequently, that is, a
allbeakerswithnitricacid.Thiscanbeaccomplishedbyeither
minimum of once per hour. Measure the flow rate with an
soaking for a minimum of 24 h in concentrated nitric acid, or
accuracy of 65% using the calibrated flowmeter, and record
by the following procedure: fill beakers to one-third capacity
the measured value.
with concentrated nitric acid, and then heat them at a hot plate
9.3.4 Attheendofthesamplingperiod,terminatesampling,
surface temperature of 140°C in a fume hood until most of the
and measure the flow rate with an accuracy of 65% using the
liquid has evaporated, and allow to cool. Rinse beakers
calibrated flowmeter. Consider the sample to be invalid if the
thoroughly with water.
flow rate was not maintained to within 65% of the nominal
10.1.3 Glassware that has been previously subjected to the
value throughout the sampling period. Record the volumetric
entire cleaning procedure described in the previous steps, and
flow rate and the time, and calculate the duration of the
which has been reserved for the analysis of hexavalent
sampling period.
chromium, can be cleaned adequately by rinsing with nitric
9.3.4.1 If an integral timer is used, check the reading on the
acid wash solution and then with water.
integral timer. Consider the sample to be invalid if this and the
10.2 Instrumental Set-Up:
calculated sampling time do not agree to within 65%, since
10.2.1 Set up the ion chromatograph in accordance with
this suggests that the sampling pump was not operating
manufacturer’s instructions.
throughout the entire sampling period.
10.2.2 Install the organic guard column and separator col-
9.3.5 Reseal the sampler and disconnect it from the sam-
umns in the ion chromatograph.
pling pump.
10.2.3 Installa1mL sample loop on the injection valve of
9.3.6 Recordsampleidentityandallrelevantsamplingdata.
the ion chromatograph.
Calculate the average flow rate by averaging the flow rate
10.2.4 Adjust the eluant flow rate to that recommended by
measurements taken before and after (and perhaps during) the
the manufacturer of the instrument. Increase the flow of the
sampling period. Compute the volume of air sampled in litres
diphenylcarbazide (DPC) reagent solution until the flow rate
by multiplying the mean flow rate (in L/min) by the sampling
reaches that recommended by the instrument manufacturer.
time (min).
9.3.7 For each batch of ten samples (or less), submit for
NOTE 22—It is recommended that the ratio of the flow rate of the DPC
analysis at least two unused filters (blanks) from the same lot reagent solution to that of the eluent remain the same.
D6832 − 13 (2018)
10.2.5 Measure the pH of the detector effluent, and ensure 11.1.2.1 Open each sampler or sample container, and trans-
thattheeffluentpHis2(byadditionofsulfuricorhydrochloric fer each filter sample or blank into a clean, labeled 50 mL
acid) or lower. The pH needs to be strongly acidic to ensure a beaker using flat-tipped forceps. If the sampler used was of a
quantitative reaction of DPC with Cr(VI). type in which airborne particles deposited on the internal
10.2.6 Adjust the visible detector to read at 540 nm. surfaces of the sampler form part of the sample, wash any
10.2.7 After the flow rates are adjusted, allow the system to particulate matter adhering to the internal surfaces into the
equilibrate for at least 15 min. beaker using a minimum volume of extraction buffer solution
(see 8.1.12.1).
11. Procedure
11.1.2.2 Add 10 mL of extraction solution (8.1.12.1), 2%
11.1 Preparation of Sample and Blank Solutions—Samples (m/v)sodiumhydroxide/3%(m/v)sodiumcarbonate0.05(pH
and blanks shall be prepared for subsequent analysis by using
13), to each beaker containing filter samples or blanks. Ensure
either a procedure for soluble hexavalent chromium or a that the filters are completely immersed in the extraction
procedure for insoluble hexavalent chromium. The former
solution.
procedure entails extraction in water or sulfate buffer solution,
11.1.2.3 Place the beakers containing the filters and extrac-
while the latter involves hot plate digestion in car
...