ASTM D5281-98
(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
SCOPE
1.1 This test method covers the collection and measurement of hexavalent chromium [CR(VI)] in ambient, workplace, or indoor atmospheres.
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 [mu]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 of 0.2 to 100 ng/m of hexavalent chromium in the atmosphere assuming 20 m 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:D 5281–98
Standard Test Method for
Collection and Analysis of Hexavalent Chromium in Ambient
Atmospheres
This standard is issued under the fixed designation D 5281; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D3195 Practice for Rotameter Calibration
D3586 Test Method for Chromium in Workplace Atmo-
1.1 Thistestmethodcoversthecollectionandmeasurement
spheres (Colorimetric Method)
of hexavalent chromium [Cr(VI)] in the ambient atmosphere.
1.2 This test method collects and stabilizes atmospheric
3. Terminology
hexavalent chromium using an alkaline impinger buffer solu-
3.1 Definitions:
tion in a wet impingement sampling technique. Lead chromate
3.1.1 For definitions of terms used in this test method, refer
[PbCrO ], generally considered poorly soluble in water, is
to Terminology D1356.
soluble in the impinger solution up to 940 µg/L as hexavalent
3.2 Definitions of Terms Specific to This Standard:
chromium.
3.2.1 eluent—the ionic mobile phase used to transport the
1.3 This test method measures hexavalent chromium using
sample through the ion exchange column.
an ion chromatographic separation combined with a post
3.2.2 resolution—the ability of a column to separate con-
separationreactionwithacolorimetricreagentandphotometric
stituents under specified test conditions.
detection.
1.4 This test method is applicable in the range from 0.2 to
4. Summary of Test Method
100 ng/m of hexavalent chromium in the atmosphere assum-
3 4.1 Sample Collection:
ing20m ofairsample.Therangecanbeextendedupwardsby
4.1.1 Air is drawn at a rate of 15 L/min over a continuous
appropriate dilution.
24-h period through three 500-mL glass impingers (in-line)
1.5 The values stated in SI units are to be regarded as the
filled with 0.02 N sodium bicarbonate [NaHCO ] “buffer”
standard. The inch-pound units given in parentheses are for
solution. A target air volume of 20 m is sampled.
information only.
4.1.2 Impinger buffer solution has a pH of 8.2 and was
1.6 This standard does not purport to address all of the
selected to prevent hexavalent chromium from being reduced
safety concerns, if any, associated with its use. It is the
to trivalent chromium [Cr(III)] in an acidic medium during
responsibility of the user of this standard to establish appro-
sampling (4).
priate safety and health practices and determine the applica-
4.1.3 The impinger buffer solution from each impinger is
bility of regulatory limitations prior to use.
analyzed for hexavalent chromium.
4.2 Sample Analysis (1, 2, 3, 4) :
2. Referenced Documents
4.2.1 A volume of filtered sample, typically 1 mL, is
2.1 ASTM Standards:
2 injected into the eluent flow path and separated by anion
D1193 Specification for Reagent Water
exchange using an ammonium sulfate [(NH ) SO ] based
4 2 4
D1356 Terminology Relating to Sampling andAnalysis of
3 eluent.
Atmospheres
4.2.2 After separation, the sample is reacted with an acidic
D1357 Practice for Planning the Sampling of the Ambient
3 solution of diphenylcarbohydrazide. Hexavalent chromium
Atmosphere
reacts selectively with this reagent to form the characteristic
D2914 Test Methods for Sulfur Dioxide Content of the
3 violet colored complex.
Atmosphere (West-Gaeke Method)
4.2.3 The eluent stream passes through a photometric de-
tector for detection of the chromium diphenylcarbohydrazide
1 complex by visible absorbance at 520 nm. Absorbance is
This test method is under the jurisdiction of ASTM Committee D22 on
proportional to the hexavalent chromium concentration.
Sampling andAnalysis ofAtmospheres and is the direct responsibility of Subcom-
mittee D22.03 on Ambient Atmospheres and Source Emissions.
Current edition approved October 10, 1998. Published December 1998. Origi-
e1 4
nally published as D5281–92. Last previous edition D5281–92 (1997) . Discontinued; See 1991 Annual Book of ASTM Standards, Vol 11.03.
2 5
Annual Book of ASTM Standards, Vol 11.01. The boldface numbers in parentheses refer to a list of references at the end of
Annual Book of ASTM Standards, Vol 11.03. the text.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 5281–98
5. Significance and Use 7.1.1 Impinger Sampling Train—For a schematic drawing
of the major sampling train components see Fig. 1. The
5.1 Hexavalent chromium has been shown to be a human
sampling train for collecting particulate matter and hexavalent
respiratory carcinogen in epidemiological studies when hu-
chromium consists of the following elements:
mans are exposed to relatively high airborne concentrations.
7.1.1.1 Impingers—Three 500-mL impingers (in-line) are
Such high exposures may also induce dermal sensitization to
usedinthesamplingtrain.Thefirsttwoimpingersintheseries
hexavalent chromium in humans (5).
(A and B) use nozzled impinger inlets with impaction plates.
5.2 Ambient atmospheric concentrations of hexavalent
These impingers impinge air at high velocity against the
chromiumarewellbelowdetectionlimitsofsamplingmethods
impaction plate creating smaller air bubbles which provide
including Test Method D3586 and NIOSH-7600 (1).
moresurfaceareaforaircontactwithbuffersolution.Thethird
5.3 Objective assessment of ambient atmospheric concen-
impinger(C)hasastraightinletnozzleandnoimpactionplate.
trations of hexavalent chromium provides a means of evaluat-
7.1.1.2 Impinger Buffer Solution—0.02 N sodium bicarbon-
ing exposures to atmospheric hexavalent chromium in a
ate buffer solution (see 8.3.1) is added to the impingers such
manner that can be related to health-based risk levels. Collect-
that: Impinger A=250 mL, B=200 mL, and C=150 mL.
ing such actual monitoring data reduces or eliminates the need
These particular impinger sodium bicarbonate solution vol-
for theoretical resuspension modeling and provides improved
umes are recommended to minimize post sample volume
basis for health assessments of potential exposures (5).
disparities between impingers.
5.4 The buffered impinger sampling technique provides pH
7.1.2 The sampling train apparatus is interconnected by the
controlofthesamplingmedium,whichstabilizestheoxidation
following elements:
state of hexavalent chromium during sampling (6).
7.1.2.1 Sample Line/Probe—Sampleisdrawnfromambient
5.5 Ion chromatography provides a means of separating the
air through a sample line/probe that consists of a 100 to
hexavalentchromiumfromotherspeciespresentinthesample,
150-mm polytetrafluoroethylene (PTFE) tube (12-mm ( ⁄2-in.)
many of which interfere with other detection methods. The
outside diameter and 9-mm ( ⁄8-in.) inside diameter). The
combination of this separation with a sensitive colorimetric
sample line/probe is inserted into the air inlet of the first
detection method provides a selective and sensitive analytical
Impinger (A).
method for hexavalent chromium with minimal sample prepa-
7.1.2.2 ImpingersA, B, and C are interconnected using two
ration (4).
glass impinger U-joints. The last impinger in the series (C) is
6. Interferences
connected to the sample pump by means of vinyl tubing using
6.1 Reducing agents may reduce hexavalent chromium to a glass 0.5p radian (90°) angle impinger joint that adapts the
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.
−1
6.5 Permanganate [MnO ] (0.5 µg/L) causes a positive
0.07-µg/L interference with hexavalent chromium.
6.6 No other interferences were observed from 10 µg/L
− −2 − −2 −3 + +2 +2 +
BrO , MoO , ClO ,S O ,VO ,Be ,Cu ,Ni ,Ag ,
3 4 4 2 8 4
+3 +3 +3 +2 +2 +2 +3 +5 +3 +2
Tl ,V ,As ,Ba ,Cd ,Co ,Cr ,Mo ,Sb ,Zn ,
+2 − − − − − −4 −2
Pb ,F ,Cl ,Br ,NO ,NO ,P O ,SO , 100 mg/L Se,
3 2 2 6 4
or 1 mg/L Hg (6).
7. Apparatus
7.1 Sampling Apparatus: FIG. 1 Diagram of a Sampling Train and Sampling Apparatus
D 5281–98
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.
7.1.3.2 Leakless Sample Pump—A vane-axial electrically
operated sampling pump capable of drawing 10 to 18 L/min of
air through the sampling train over 24 h is suitable.
7.1.3.3 Flow Control Device—Air flowrate control can be
enhancedusingacriticalorificeordrygasmeterinaccordance
with Test Methods D2914. Protect the orifice or gas meter
from particulate matter (see 11.2.6).
7.1.4 Bubble Meter—Thebubblemeterisusedasaprimary
methodofsamplingtrainairflowratecalibration(see10.1)and
shall be capable of reading sampling air flowrates of 2 to 30
L/min.Connectthebubblemetertothesampleline/probewith
FIG. 2 Diagram of an Ion Chromatograph Using Post-Column
a flexible rubber tube.
Reagent Addition and Photometric Detection
7.1.5 An elapsed time meter is placed in line with the
sample pump to assist in detection of electrical interruptions
7.2.1.3 Guard Column—A column placed before the sepa-
that could have occurred over the 24 h interval.
rator column to protect the separator column from fouling by
7.1.6 Stop Watch or Timer.
particles or strongly absorbed organic constituents.
7.1.7 pH Meter, to measure the pH of the impinger buffer
7.2.1.4 Separator Column—A column packed with high
solution.
capacity pellicular anion exchange resin that is suitable for
7.1.8 Refrigerator or Ice Cooler, for storage of samples
resolving hexavalent chromium from a sample containing high
prior to shipment to the laboratory (see 11.4).
total dissolved solids (for example, 3% Na SO ).
2 4
7.1.9 Ice Cooler, for transport of samples to the laboratory
7.2.1.5 Reagent Delivery Module—A device capable of
(see 11.4).
delivering 0 to 2 mL/min of reagent against a backpressure of
7.1.10 Meteorological Weather Station or Weather Data
up to 40 kPa (6.0 lb/in. ).
Service, to determine ambient temperature, pressure, relative
7.2.1.6 Mixing Tee and Reaction Coil—Adevice capable of
humidity, wind speed and direction, and precipitation (see
mixing two flowing streams with minimal band spreading.
11.2.7).Thisinformationmaybeusefultointerpretdata,butis
7.2.1.7 Detector—A low-volume, flow-through visible ab-
not required to correct data for standard conditions.
sorbance detector with a nonmetallic 1-cm flow path. The
7.2 Analytical Apparatus (4):
detection wavelength for hexavalent chromium is 520 nm.
7.2.1 Ion Chromatograph—The ion chromatograph shall 7.2.1.8 Recorder, Integrator, or Computer—A device com-
have the following components as shown in Fig. 2.
patible with detector output, capable of recording detector
7.2.1.1 Pump, capable of delivering a constant flow in the response as a function of time for the purpose of measuring
range of 1 to 5 mL/min at a pressure of 15 to 150 MPa (200 to peak height or area.
2000 lb/in. ). 7.2.2 Eluent Reservoir—A container suitable for storing
7.2.1.2 Injection Valve—Alow dead-volume valve that will eluent.
allow the loading of a sample contents into the eluent stream. 7.2.3 0.45 µm syringe filter, for sample filtration prior to
Sample loops of up to 1 mL will provide enhanced detection analysis (see 11.5.7).
limits. Smaller sample loops will result in proportionally 7.2.4 Syringe—Asyringeequippedwithamalefittinganda
higher detection limits. capacity of at least 1 mL or auto sampler module (see 11.5.8).
D 5281–98
8. Reagents and Materials 9.2 To assess ambient environmental concentrations of
hexavalent chromium, collect samples with a target air volume
8.1 Purity of Reagents—Reagent grade chemicals shall be
of 20 m over a continuous 24-h sampling interval.
usedinalltests.Allreagentsshallconformtothespecifications
9.3 FieldQualityAssuranceandControlSamples(QA/QC):
of the Committee on Analytical Reagents of the American
Chemical Society where such specifications are available.
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—0.02Nsodiumbicarbonate
9.5 For general information on sampling refer to Practice
buffer solution: dissolve 1.67 g of sodium bicarbonate
D1357.
(NaHCO ) in 1 L of reagent water.
8.3.2 Impinger Buffer Solution Spike—Prepared in 0.5, 1,
10. Calibration and Standardization
and 10-µg/Lconcentrations by diluting appropriate volumes of
10.1 Sampling Calibration:
the 1000 µg/Lhexavalent chromium standard (see 8.2.2) in the
buffer solution (see 8.3.1). 10.1.1 Calibratesampleairflowrateusingaprimarymethod
8.3.3 1 % Nitric Acid Wash Solution—Dilute 10 mL of
of calibration at the beginning (pre-calibration) and end (post-
concentrated reagent grade nitric (HNO ) acid, sp gr 1.42, to 1
...
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