United States
Environmental Protection
Agency
Environmental Sciences^
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S3-84-058 June 1984
4>EPA Project Summary
Method for Collection and
Analysis of Chlorobenzenes
G. W. Wooten, J. E. Strobel, R. C. Gable, J. V. Pustinger, and C. R. McMillin
To measure individual exposures to
potentially hazardous organic
compounds including halogenated
hydrocarbons and benzene, personal
monitors using sorbent-based passive
samplers (passive exposure monitors)
and analytical methodology using gas
chromatographic analytical techniques
were developed. The sampling/
analytical techniques were evaluated
under laboratory conditions with
generated vaporous samples of known
concentration for the compounds of
interest and optimized for detection and
quantitation. The passive dosimeter
and analytical technique used for this
project was found to be capable of
detecting 0.5 ppb of the subject
compounds after as little as one-half
hour of sampling. Passive dosimeter
results correlated well with results
obtained on pumped sorbent tubes
collected in parallel. The sampling/
analytical methods were further
validated with field samples, focusing
on a quantitative analysis of the
halogenated hydrocarbons and
benzene.
This Project Summary was developed
by EPA's Environmental Sciences Re-
search Laboratory, Research Triangle
Park, NC. to announce key findings of
the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
The U.S. EPA instituted the Public
Health Initiative (PHI) in 1980 with the
goal of establishing an ongoing human
exposure monitoring capability within the
EPA. The basic approach of this program
is to measure individual exposures to
toxic substances through the main
exposure pathways of air, drinking water,
and food The ultimate results of the
initiative will be a field-tested
methodology for measuring human
exposure to toxic substances in defined
geographical areas.
This report addresses one portion of the
PHI program, the development of
atmospheric monitoring techniques for
potentially hazardous organic
compounds, including chloroform,
chlorobenzene, benzene, carbon tetra-
chloride, 1,1,1-tnchloroethane, 1,1-
dichloroethane, tetrachloroethylene, and
trichloroethylene.
In conjunction with another EPA
contract, Monsanto Research Corpora-
tion (MRC) developed the passive
exposure monitor (PEM or passive
dosimeter) as a sampling device to
measure the exposure to halogenated
hydrocarbon and benzene compounds at
low concentrations (low parts per billion
level). Experimental test chambers were
built to test the PEMs to demonstrate
sensitivity and specificity of the approach
Laboratory studies also were conducted
to define the effects of ultraviolet light,
water, and ozone on the chemical integ-
rity of the compounds of interest m
generated vaporous samples.
Procedures
Three test facilities were constructed to
test the dosimeters and identify their
sensitivity to various compounds. These
facilities included a standard generation
system, a laboratory test exposure
chamber, and an environmental test
chamber. Standards were prepared by
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mixing stock solutions of compounds
diluted to various volumes. Both liquid
and gas standards could be generated
using the syringe drive of fluids into a
heated block with three calibrated
dilution stages
The laboratory test exposure chamber
consisted of a two-liter Pyrex reaction
kettle filled with an "O"-ring-sealed
Teflon lid, and three ports for gas inlet,
gas outlet, and temperature and humidity
monitoring The chamber provides for
evaluation of the dosimeter capabilities
under the lab chamber conditions. The
passive dosimeter is inserted into the
Pyrex chamber, the chamber is sealed,
and the standard gas is passed through
the chamber at defined rates and
durations. Effluent gas passes through a
sorbent tube and measurements are
made of the particular organic compound
for mass in, mass out, and mass absorbed
by the dosimeter.
The environmental test chamber
consisted of a thick-walled, flanged Pyrex
pipe in a concentric tube arrangement in
which the gas flowed down the center
tube, back through the space separating
the two tubes, and down the center tube
again. This facility provided for the
detailed evaluation of the effects of temp-
erature, humidity, and flow velocities, all
of which could be controlled and
monitored
MRC developed a miniature passive
dosimeter containing a solid sorbent.
Chlorinated organic vapors diffuse to the
solid sorbent in the dosimeter and are
thereby concentrated over a period of
time. Subsequently, the trapped vapors
are removed by thermal desorption and
quantitated via gas chromatography (GC)
or tandem-coupled gas chromatography/
mass spectroscopy (GC/MS) or a specific
detector (i.e., electron capture or
photoionization). Solid porous polymers
have found wide acceptance as means for
collecting and concentrating organic
compounds in ambient air and other
sampling environments. Sorbent-based
active (pump-drive) sampling systems as
well as passive sampling devices are
customarily employed for such
assignments where compound concen-
trations are encountered.
Application of the solid sorbent
sampling approach to specific sampling
problems involved three principal areas
of technology: pump rates and/or
diffusion considerations, sorbent
selection, and chemical quantitation of
sampled compounds. The latter area
intimately involved desorption of the
compounds from the sorbent sampling
tube or passive device.
2
Basically, the passive dosimeter
consists of a stainless steel body, with a
3.8-cm outer diameter, a 3.5-cm inner
diameter and 1 1 cm high. The stainless
steel construction makes the device
amenable to thermal desorption, avoids
possible absorbance or reactant
problems associated with plastic
materials, and provides a rugged, strong
device. Two stainless steel screens (200-
mesh) and two perforated plates (28%
open area) on each side of the polymer
serve to confine the polymer within the
dosimeter body and provide diffusion
barriers. A measured amount of sorbent
(~0.4 g) commonly Tenax GC, is used in
the dosimeter. Friction snap rings seal
the screens and backup plates on each
side of the adsorbent within the
dosimeter body.
The thermal desorption oven required
for dosimeter desorption/analysis was
designed to ensure reliable performance,
to handle a large number of dosimeters,
and to handle the desorption of sorbent
sampling tubes (dynamic flow) as well as
the newly designed passive dosimeters.
The oven unit operates based on two
manual high-temperature (300°C max)
Valco valves which direct helium purge
gas through either the sorbent tube or the
passive dosimeter path to the second
valve that selects the "desorb/trap" or
"analyze" mode of operation. The
"desorb/trap" mode diverts the purge
gas through a cryogenically cooled
sample loop to provide off-line trapping
which, in addition, provides better carrier
gas flow rate control. The "analyze" mode
backflushes a second gas stream (helium
carrier gas) through the sample loop,
which is now ballistically heated to
transfer the trapped compounds to the
analytical column for high-resolution
chromatographic analysis.
Chromatographic conditions employed
for the analysis of dosimeters and sorbent
sample tubes are given in Table 1. The GC
column effluent is split and sent to both a
Hall electrolytic conductivity detector (EC)
and a photoionization detector (PID) for
selective determination of halogens and
semi-selective determination of
aromatics, respectively.
Results and Discussion
Preliminary studies were conducted to
evaluate sorbent selection. Based on
previous success in both active and
passive sampling modes Porapak R and
Tenax GC adsorbents were evaluated.
Studies of one-hour exposures of seven-
compound test gas showed Tenax GC had
recoveries exceeding 93% and was a
better choice of sorbent.
Continued development of the passive
dosimeter as a sampling device for low-
concentration hazardous organic
compounds including halogenated and
aromatic compounds was conducted and
tested extensively at the laboratory and
field scale under several EPA-MRC
contracts. The development work results
are presented in the reports of the EPA
contract number 68-02-3469 and 68-02-
3699.
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Table 1. GC/EC Detector Conditions for Dosimeter Analysis
Instrument: Chromatograph: Hewlett-Packard Model 5711
Hall Detector Tracor Model 700 fin chlorine mode)
Auto Sampler: Hewlett-Packard Model 7671 -A
Column 2.44- x 2-mm (ID) glass packed with 1% SP1000 on 60/80 mesh Carbopak B
Temperature Program: 60 to 210°C at 8°C/min, hold at 2W°C for 15 min
Other Conditions:
Parameter
Injection Port
Transfer Line
Hall Reactor
Temperature, °C
200
250
850
Flow rate, mL/min
Helium (carrier) 40
Hydrogen (reactor gas) 45
Electrolyte (n-propanol) 0.75
G. W. Wooten, J. E. Strobe/, R. C. Gable. J. V. Pustinger, and C. R. McMillin are
with Monsanto Company, Dayton, OH 45407.
Bruce W. Gay, Jr., is the EPA Project Officer (see below).
The complete report, entitled "Method for Collection and Analysis of Chloro-
benzenes," (Order No. PB 84-189 646; Cost: $8.50, subject to change) 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:
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
•(ir U S GOVERNMENT PRINTING OFFICE, 1984 — 759-01 5/7723
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