United States
Environmental Protection
Agency
Atmospheric Research and
Exposure Assessment Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/SR-93/053 September 1993
«rEPA Project Summary
Evaluation of Portable
Multisorbent Air Samplers for
Use With An Automated
Multitube Analyzer
Albert J. Pollack, Sydney M. Gordon, and Demetrios J. Moschandreas
The objective of this study was to
evaluate the operational characteris-
tics of two portable ambient air sam-
plers. Both the Perkin Elmer
Sequential Tube Sampler (Model STS
25) and the IITRI/IIT (NT Research In-
stitute/Illinois Institute of Technology)
Total Isolated-by-Microenvironment
Exposure (TIME) monitor made use of
multisorbent carbon-based sampling
tubes to collect volatile organic com-
pounds in air samples. In order to
process the collection tubes, meth-
ods development was performed us-
ing a Perkin Elmer Auto Thermal
Desorptipn System (Model ATD 400).
The volatile organic compounds (VOCs)
listed in the EPA TO-14 method were
the target species. Details of the study
are presented along with recommenda-
tions for further evaluation and devel-
opmental efforts for these samplers and
the sorbent/analytical methodology.
This report was submitted in fulfill-
ment of Contract No. 68-DO-0007 by
Battelle Columbus Operations under
sponsorship of the U.S. Environmental
Protection Agency. This report covers a
period from March 1992 to September
1992, and work was completed as of
September 15, 1992.
Introduction
Recognition of the importance of
trace-level VOCs in breathing-zone air and
their potential impact on human health
has stimulated interest in methods for char-
acterizing these compounds. Most tech-
niques in use today for measuring VOC
concentrations have their origin in indus-
trial hygiene monitoring methods. They
generally rely on solid sorbents or canis-
ters to collect whole-air samples.
Long term integrative sample collection
is the preferred approach for measuring
relatively constant emissions and for as-
sessing average exposure, such as in stud-
ies of chronic health effects. However, to
obtain detailed documentation of temporal
or spatial changes, as in the case of inter-
mittent emissions or acute exposures,
short and frequent sampling periods in
various locations in which exposure may
occur are more appropriate. To this end,
portable air sampling devices, such as the
STS 25 and TIME monitor, are being de-
veloped to permit the collection of toxic air
pollutants on a schedule best suited to
identify and characterize exposure occur-
rences.
Objective
The objective of this study was to evalu-
ate the performance of the STS 25 and
TIME monitor for collecting VOCs on
carbon-based sorbent tubes and process-
ing these tubes using the Perkin Elmer
(ATD 400) system. Methods development
and validation of the sorbent system used
in this study were completed before the
sampler evaluations were undertaken.
Evaluation
Carbon-based sorbents were exam-
ined for their ability to collect the
TO-14 compounds in humidified air
samples up to 3 L in volume. In addi-
tion, an analytical procedure was devel-
oped using the Perkin ATD 400 desorption
system to process the sample collection
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tubes in an automated fashion. The AID
400 was coupled to a gas chromatograph
that was fitted with a thick-film capillary
column. This analytical scenario was in-
vestigated to determine if it was possible
to resolve the target compounds without
the use of cryogen.
Two portable air samplers were evalu-
ated using the multisorbent collection tube
and analytical method developed during
the first phase of this study. The STS 25
was subjected to mechanical tests, col-
lecting samples under controlled labora-
tory conditions, and indoor/outdoor
sampling. The TIME monitor was oper-
ated to confirm its ability to recognize dif-
ferent environments and used to collect
air samples.
Conclusions and
Recommendations
Laboratory tests confirmed that the
TO-14 compounds could be collected on
a three-stage sorbent bed composed of
Carbotrap C, Carbotrap, and Carbosieve
S-lll. Indications were that only partial
breakthrough for the most volatile target
species was taking place for sample vol-
umes up to 3 L. The analytical method
developed was able to resolve the TO-14
compounds without the use of cryogen
with very good precision. A limitation of
the analytical system was that misidentifi-
cation of compounds occurred when com-
plex samples were analyzed. The
qualitative and quantitative results were
obtained using only a flame ionization de-
tector (FID) that relied upon retention times
for peak identification. If coeluting
non-target compounds were present in a
sample, they were mistakenly identified
as compounds of interest.
The STS 25 performed without any me-
chanical problems during its evaluation.
During the laboratory chamber tests, the
STS 25 showed that it could collect TO-14
compounds on the multisorbent tubes un-
der various sampling conditions. However,
the confined environment of the chamber
indicated that the STS 25 has the poten-
tial of introducing artifacts into the sam-
pling environment. When the STS 25 was
used to collect indoor and outdoor
samples, under more realistic operating
conditions, the results obtained for the
target compounds were in good agree-
ment with those obtained with conven-
Albert J. Pollack and Sydney M. Gordon are with Battelle, Columbus, OH 43201.
Demetrios J. Moschandreas is with Illinois Institute of Technology, Chicago, IL
60616-3799.
William A. McClenny and James D. Mulik are the EPA Project Officers (see
below).
The complete report, entitled "Evaluation of Portable Multisorbent Air Samplers for
Use With An Automated Multitube Analyzer," (Order No. PB93-172930; Cost:
$19.50), will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
tional canisters, and the artifact effects
were no longer observed. The limitation of
the FID was again noted during these air
sampling tests.
The TIME monitor was redesigned be-
fore undergoing any evaluation. The re-
sponse time of the sensing transducer to
a change in environment was shortened,
and the size and weight of the unit was
reduced. The system showed that it rec-
ognizes changes in its environment as it
is transported from outdoor to indoor loca-
tions. The air samples collected were pro-
cessed and provided information on
specific environments as the source of
exposure to selected toxic compounds.
We recommend that to more precisely
evaluate the capabilities of the sorbents
and samplers used during this study, the
ATD 400 be connected to an analytical
system that incorporates a mass selective
or ion trap detector. We also suggest that
field tests of the STS 25 and TIME sam-
plers continue, along with the develop-
ment of collection tubes and analytical
methods that will provide data on other
compounds such as polar organics and
the C2-C4 ozone precursors.
•U.S. Government Printing Office: 1993 — 750-071/80101
BULK RATE
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EPA
PERMIT No. G-35
EPA/600/SR-93/053
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