ASTM D5281-98(2005)
(Test Method)Standard Test Method for Collection and Analysis of Hexavalent Chromium in Ambient Atmospheres
Standard Test Method for Collection and Analysis of Hexavalent Chromium in Ambient Atmospheres
SIGNIFICANCE AND USE
Hexavalent chromium has been shown to be a human respiratory carcinogen in epidemiological studies when humans are exposed to relatively high airborne concentrations. Such high exposures may also induce dermal sensitization to hexavalent chromium in humans (5).
Ambient atmospheric concentrations of hexavalent chromium are well below detection limits of sampling methods including Test Method D 3586 and NIOSH-7600 (1).
Objective assessment of ambient atmospheric concentrations of hexavalent chromium provides a means of evaluating exposures to atmospheric hexavalent chromium in a manner that can be related to health-based risk levels. Collecting such actual monitoring data reduces or eliminates the need for theoretical resuspension modeling and provides improved basis for health assessments of potential exposures (5).
The buffered impinger sampling technique provides pH control of the sampling medium, which stabilizes the oxidation state of hexavalent chromium during sampling (6).
Ion chromatography provides a means of separating the hexavalent chromium from other species present in the sample, many of which interfere with other detection methods. The combination of this separation with a sensitive colorimetric detection method provides a selective and sensitive analytical method for hexavalent chromium with minimal sample preparation (4).
SCOPE
1.1 This test method covers the collection and measurement of hexavalent chromium [Cr(VI)] in the ambient atmosphere.
1.2 This test method collects and stabilizes atmospheric hexavalent chromium using an alkaline impinger buffer solution in a wet impingement sampling technique. Lead chromate [PbCrO4], generally considered poorly soluble in water, is soluble in the impinger solution up to 940 g/L as hexavalent chromium.
1.3 This test method measures hexavalent chromium using an ion chromatographic separation combined with a post separation reaction with a colorimetric reagent and photometric detection.
1.4 This test method is applicable in the range from 0.2 to 100 ng/m3 of hexavalent chromium in the atmosphere assuming 20 m3 of air sample. The range can be extended upwards by appropriate dilution.
1.5 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D5281 − 98(Reapproved 2005)
Standard Test Method for
Collection and Analysis of Hexavalent Chromium in Ambient
Atmospheres
This standard is issued under the fixed designation D5281; 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 D1357Practice for Planning the Sampling of the Ambient
Atmosphere
1.1 Thistestmethodcoversthecollectionandmeasurement
D2914Test Methods for Sulfur Dioxide Content of the
of hexavalent chromium [Cr(VI)] in the ambient atmosphere.
Atmosphere (West-Gaeke Method)
1.2 This test method collects and stabilizes atmospheric
D3195Practice for Rotameter Calibration
hexavalent chromium using an alkaline impinger buffer solu-
D3586Test Method for Chromium in Workplace Atmo-
tion in a wet impingement sampling technique. Lead chromate 3
spheres (Colorimetric Method) (Withdrawn 1990)
[PbCrO ], generally considered poorly soluble in water, is
soluble in the impinger solution up to 940 µg/L as hexavalent
3. Terminology
chromium.
3.1 Definitions:
1.3 This test method measures hexavalent chromium using
3.1.1 For definitions of terms used in this test method, refer
an ion chromatographic separation combined with a post
to Terminology D1356.
separationreactionwithacolorimetricreagentandphotometric
3.2 Definitions of Terms Specific to This Standard:
detection.
3.2.1 eluent—the ionic mobile phase used to transport the
sample through the ion exchange column.
1.4 This test method is applicable in the range from 0.2 to
100 ng/m of hexavalent chromium in the atmosphere assum- 3.2.2 resolution—the ability of a column to separate con-
ing20m ofairsample.Therangecanbeextendedupwardsby stituents under specified test conditions.
appropriate dilution.
4. Summary of Test Method
1.5 The values stated in SI units are to be regarded as the
4.1 Sample Collection:
standard. The inch-pound units given in parentheses are for
4.1.1 Air is drawn at a rate of 15 L/min over a continuous
information only.
24-h period through three 500-mL glass impingers (in-line)
1.6 This standard does not purport to address all of the
filled with 0.02 N sodium bicarbonate [NaHCO ] “buffer”
safety concerns, if any, associated with its use. It is the
solution. A target air volume of 20 m is sampled.
responsibility of the user of this standard to establish appro-
4.1.2 Impinger buffer solution has a pH of 8.2 and was
priate safety and health practices and determine the applica-
selected to prevent hexavalent chromium from being reduced
bility of regulatory limitations prior to use.
to trivalent chromium [Cr(III)] in an acidic medium during
sampling (4).
2. Referenced Documents
4.1.3 The impinger buffer solution from each impinger is
2.1 ASTM Standards:
analyzed for hexavalent chromium.
D1193Specification for Reagent Water
4.2 Sample Analysis (1, 2, 3, 4) :
D1356Terminology Relating to Sampling and Analysis of
4.2.1 A volume of filtered sample, typically 1 mL, is
Atmospheres
injected into the eluent flow path and separated by anion
exchange using an ammonium sulfate [(NH ) SO ] based
4 2 4
This test method is under the jurisdiction of ASTM Committee D22 on Air
eluent.
Quality and is the direct responsibility of Subcommittee D22.03 on Ambient
4.2.2 After separation, the sample is reacted with an acidic
Atmospheres and Source Emissions.
solution of diphenylcarbohydrazide. Hexavalent chromium
Current edition approved March 1, 2005. Published May 2005. Originally
approved in 1992. Last previous edition approved in 1998 as D5281-98. DOI:
10.1520/D5281-98R05.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or The last approved version of this historical standard is referenced on
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM www.astm.org.
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers in parentheses refer to a list of references at the end of
the ASTM website. the text.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5281 − 98 (2005)
−1
reacts selectively with this reagent to form the characteristic 6.5 Permanganate [MnO ] (0.5 µg/L) causes a positive
violet colored complex. 0.07-µg/L interference with hexavalent chromium.
4.2.3 The eluent stream passes through a photometric de-
6.6 No other interferences were observed from 10 µg/L
tector for detection of the chromium diphenylcarbohydrazide − −2 − −2 −3 + +2 +2 +
BrO , MoO , ClO ,S O ,VO ,Be ,Cu ,Ni ,Ag ,
3 4 4 2 8 4
complex by visible absorbance at 520 nm. Absorbance is +3 +3 +3 +2 +2 +2 +3 +5 +3 +2
Tl ,V ,As ,Ba ,Cd ,Co ,Cr ,Mo ,Sb ,Zn ,
+2 − − − − − −4 −2
proportional to the hexavalent chromium concentration.
Pb ,F ,Cl ,Br ,NO ,NO ,P O ,SO ,100mg/LSe,
3 2 2 6 4
or 1 mg/L Hg (6).
5. Significance and Use
7. Apparatus
5.1 Hexavalent chromium has been shown to be a human
respiratory carcinogen in epidemiological studies when hu-
7.1 Sampling Apparatus:
mans are exposed to relatively high airborne concentrations.
7.1.1 Impinger Sampling Train—For a schematic drawing
Such high exposures may also induce dermal sensitization to
of the major sampling train components see Fig. 1. The
hexavalent chromium in humans (5).
sampling train for collecting particulate matter and hexavalent
chromium consists of the following elements:
5.2 Ambient atmospheric concentrations of hexavalent
7.1.1.1 Impingers—Three 500-mL impingers (in-line) are
chromiumarewellbelowdetectionlimitsofsamplingmethods
usedinthesamplingtrain.Thefirsttwoimpingersintheseries
including Test Method D3586 and NIOSH-7600 (1).
(A and B) use nozzled impinger inlets with impaction plates.
5.3 Objective assessment of ambient atmospheric concen-
These impingers impinge air at high velocity against the
trations of hexavalent chromium provides a means of evaluat-
impaction plate creating smaller air bubbles which provide
ing exposures to atmospheric hexavalent chromium in a
moresurfaceareaforaircontactwithbuffersolution.Thethird
manner that can be related to health-based risk levels. Collect-
impinger(C)hasastraightinletnozzleandnoimpactionplate.
ing such actual monitoring data reduces or eliminates the need
7.1.1.2 Impinger Buffer Solution—0.02 N sodium bicarbon-
for theoretical resuspension modeling and provides improved
ate buffer solution (see 8.3.1) is added to the impingers such
basis for health assessments of potential exposures (5).
that: Impinger A=250 mL, B=200 mL, and C=150 mL.
5.4 The buffered impinger sampling technique provides pH
These particular impinger sodium bicarbonate solution vol-
controlofthesamplingmedium,whichstabilizestheoxidation
umes are recommended to minimize post sample volume
state of hexavalent chromium during sampling (6).
disparities between impingers.
7.1.2 The sampling train apparatus is interconnected by the
5.5 Ion chromatography provides a means of separating the
following elements:
hexavalentchromiumfromotherspeciespresentinthesample,
many of which interfere with other detection methods. The
combination of this separation with a sensitive colorimetric
detection method provides a selective and sensitive analytical
method for hexavalent chromium with minimal sample prepa-
ration (4).
6. Interferences
6.1 Reducing agents may reduce hexavalent chromium to
trivalentchromiuminacidicmatrices.PreservationofapH7.8
or greater will minimize the effect of these species. The
oxidation of trivalent chromium to hexavalent chromium
during this test method is unlikely to occur (6).
6.2 By virtue of the chromatographic separation, essentially
all interfering species are removed from the hexavalent chro-
mium before detection. The response of 1 mg/L of hexavalent
chromium is not affected by 1000 mg/L of chromic ion.
6.3 Interferences may result from overloading of the ana-
lytical separator column capacity with high concentrations of
anionicspeciesinthesample.Concentrationsofchlorideionor
sulfate ion up to the equivalent of 2% NaCl and 5% Na SO
2 4
do not affect the separation or detection when using a 100-µL
sample loop (2).
−1
6.4 Hypochlorite [OCl ] (100 mg/L) in the buffer solution
hasbeenfoundtocauseapositiveinterferencewithhexavalent
chromiumanalysestotheextentof0.3to1µg/L.Hypochlorite
(1 mg/L) has also been found, in the presence of 50 µg/L
trivalent chromium, to cause a 1.2-µg/L positive interference
with hexavalent chromium. FIG. 1 Diagram of a Sampling Train and Sampling Apparatus
D5281 − 98 (2005)
7.1.2.1 Sample Line/Probe—Sample is drawn from ambient
air through a sample line/probe that consists of a 100 to
150-mm polytetrafluoroethylene (PTFE) tube (12-mm ( ⁄2-in.)
outside diameter and 9-mm ( ⁄8-in.) inside diameter). The
sample line/probe is inserted into the air inlet of the first
Impinger (A).
7.1.2.2 ImpingersA, B, and C are interconnected using two
glass impinger U-joints. The last impinger in the series (C) is
connected to the sample pump by means of vinyl tubing using
a glass 0.5π radian (90°) angle impinger joint that adapts the
impinger to wax film tubing (see 7.1.3). Impinger clips, wax,
andwaxfilmwrapsareusedtosecureallimpingerconnections
and prevent sampling train leaks.
7.1.3 Sampling Box—A pre-assembled impinger sampling
box holds the impinger sampling train and is designed so that
the sample line/probe protrudes outside the box and bends
downward. The sample box is fitted with vinyl tubing (14-mm
9 3
( ⁄16-in.) outside diameter and 9-mm ( ⁄8-in.) inside diameter)
that connects the impinger sampling train to a sample pump
(see7.1.2.2).Thevinyltubingisfittedwithanin-linerotameter
to facilitate sampling train operational checks.
7.1.3.1 An in-line rotameter fitted on the sample box facili-
tatesoperationalchecksofthesamplingsystem.Therotameter
is a glass variable area flow meter capable of measuring
flowrates between 10 and 15 L/min, calibrated in accordance
with Practice D3195.
FIG. 2 Diagram of an Ion Chromatograph Using Post-Column Re-
7.1.3.2 Leakless Sample Pump—A vane-axial electrically
agent Addition and Photometric Detection
operated sampling pump capable of drawing 10 to 18 L/min of
air through the sampling train over 24 h is suitable.
7.2.1.1 Pump, capable of delivering a constant flow in the
7.1.3.3 Flow Control Device—Air flowrate control can be
range of 1 to 5 mL/min at a pressure of 15 to 150 MPa (200 to
enhancedusingacriticalorificeordrygasmeterinaccordance
2000 lb/in. ).
withTestMethodsD2914.Protecttheorificeorgasmeterfrom
7.2.1.2 Injection Valve—Alow dead-volume valve that will
particulate matter (see 11.2.6).
allow the loading of a sample contents into the eluent stream.
7.1.4 Bubble Meter—The bubble meter is used as a primary
Sample loops of up to 1 mL will provide enhanced detection
methodofsamplingtrainairflowratecalibration(see10.1)and
limits. Smaller sample loops will result in proportionally
shall be capable of reading sampling air flowrates of 2 to 30
higher detection limits.
L/min.Connectthebubblemetertothesampleline/probewith
7.2.1.3 Guard Column—A column placed before the sepa-
a flexible rubber tube.
rator column to protect the separator column from fouling by
7.1.5 An elapsed time meter is placed in line with the
particles or strongly absorbed organic constituents.
sample pump to assist in detection of electrical interruptions
7.2.1.4 Separator Column—A column packed with high
that could have occurred over the 24 h interval.
capacity pellicular anion exchange resin that is suitable for
7.1.6 Stop Watch or Timer.
resolving hexavalent chromium from a sample containing high
7.1.7 pH Meter, to measure the pH of the impinger buffer total dissolved solids (for example, 3% Na SO ).
2 4
solution.
7.2.1.5 Reagent Delivery Module—A device capable of
delivering 0 to 2 mL/min of reagent against a backpressure of
7.1.8 Refrigerator or Ice Cooler, for storage of samples
up to 40 kPa (6.0 lb/in. ).
prior to shipment to the laboratory (see 11.4).
7.2.1.6 Mixing Tee and Reaction Coil—Adevice capable of
7.1.9 Ice Cooler, for transport of samples to the laboratory
mixing two flowing streams with minimal band spreading.
(see 11.4).
7.2.1.7 Detector—A low-volume, flow-through visible ab-
7.1.10 Meteorological Weather Station or Weather Data
sorbance detector with a nonmetallic 1-cm flow path. The
Service, to determine ambient temperature, pressure, relative
detection wavelength for hexavalent chromium is 520 nm.
humidity, wind speed and direction, and precipitation (see
7.2.1.8 Recorder, Integrator, or Computer—A device com-
11.2.7).Thisinformationmaybeusefultointerpretdata,butis
patible with detector output, capable of recording detector
not required to correct data for standard conditions.
response as a function of time for the purpose of measuring
7.2 Analytical Apparatus (4):
peak height or area.
7.2.1 Ion Chromatograph—The ion chromatograph shall 7.2.2 Eluent Reservoir—A container suitable for storing
have the following components as shown in Fig. 2. eluent.
D5281 − 98 (2005)
7.2.3 0.45 µm syringe filter, for sample filtration prior to 9. Sampling
analysis (see 11.5.7).
9.1 Selectasamplinglocationtoprovideinformationonthe
7.2.4 Syringe—Asyringe equipped with a male fitting and a
possible impact of site activities, conditions, and possible
capacity of at least 1 mL or auto sampler module (see 11.5.8).
humanexposures.Collectbothupwindanddownwindambient
air samples.
8. Reagents and Materials
9.2 To assess ambient environmental concentrations of
8.1 Purity of Reagents—Reagent grade chemicals shall be
hexavalent chromium, collect samples with a target air volume
usedinalltests.Allreagentsshallconformtothespecifications
of 20 m over a continuous 24-h sampling interval.
of the Committee on Analytical Reagents of the American
Chemical Society where such specifications are available. 9.3 FieldQualityAssuranceandControlSamples(QA/QC):
9.3.1 FieldQA/QCsamplescollectedinclude:oneimpinger
8.2 Purity of Water—Water shall be Type II reagent water
fieldblankforeverysamplingperiod(see11.1.2.4and12.3.2).
conforming to Specification D1193.
9.4 Sampling collection and analytical procedures are de-
8.3 Sampling Reagents and Materials:
scribed in Section 11.
8.3.1 Impinger Buffer Solution—0.02 N sodium bicarbonate
buffer solution: dissolve 1.67 g of sodium bicarbonate
9.5 For general information on sampling refer to Practice
(NaHCO ) in 1 L of reagent water.
D1357.
8.3.2 Impinger Buffer Solution Spike—Prepared in 0.5, 1,
and 10-µg/Lconcentrations by
...
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