United States
                    Environmental Protection
                    Agency
Environmental Monitoring
Systems Laboratory
Research Triangle Park NC 27711
                    Research and Development
EPA-600/S4-84-050 Aug. 1984
SEPA          Project  Summary
                    Passive  Sampling  Device  for
                    Ambient Air  and  Personal
                    Monitoring

                    G.W. Wooten, J.E. Strobel, J.V. Pustinger, and C.R. McMillin
                      A high performance passive dosim-
                    eter has been developed and evaluated
                    as a monitor  for volatile organics in
                    ambient air and for short-term, low-
                    level personal monitoring applications.
                    The dosimeter design was dictated by
                    three major areas of concern: (1)
                    diffusive mass transport considerations;
                    (2) sorbent selection, and (3) chemical
                    quantitation of the collected compounds,
                    which intimately involves desorption
                    procedures of the passive device.
                      Salient design features of the dosim-
                    eter included the following: (1) rugged,
                    simple design  and cost effective; (2)
                    small size and simple operation; (3)
                    high  equivalent pump rate  and high
                    sensitivity; (4) multicomponent sampling
                    capability; (5) ability to be reused and
                    recharged;  and (6)  amenability to
                    thermal desorption.
                      The results of laboratory  and field
                    evaluation studies of dosimeter perform-
                    ance are discussed in terms of the
                    design criteria employed in the develop-
                    ment of the device and its application to
                    widely divergent sampling assignments.
                    Detection sensitivity at the sub-ppb
                    level was demonstrated  for short
                    exposure times (e.g., one hour) employ-
                    ing  thermal desorption and halogen
                    specific Hall detector/gas chromatog-
                    raphy.  Long-term exposures were
                    conducted  under ambient air (ppb
                    range) and work  station (ppm  range)
                    environmental conditions.  Retention
                    time windows and detector response
                    factors for 24 halogenated compounds
                    have been established for our computer
                    program to increase compound recog-
                    nition capabilities. The addition of a
                    photoionization detector extended this
capability to nonhalogen compounds of
current environmental interest.
  This Project Summary was developed
by EPA's Environmental Monitoring
Systems Laboratory. Research Triangle
Park. NC to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title  (see  Project  Report ordering
information at back).

Introduction
  The rapidly expanding needs of personal
and area monitoring demand passive
monitoring devices that offer the capability
of detecting multicomponent vapors at
low concentrations  and are low-cost,
lightweight, and convenient units. Pro-
perly designed passive dosimeters con-
taining selected  polymeric adsorbents
can provide highly attractive performance
with respect to multivapor capability and
sensitivity to ppb levels.
  The  objective of this program was to
design, develop and evaluate a prototype
passive personal  dosimeter based on
diffusion principles and employing porous
polymer sorbents that will meet all of the
performance requirements stated above.
The personal dosimeterwas to be capable
of monitoring the  following toxic organic
pollutants at the part-per-billion level in
ambient air: benzene, vinyl chloride, tri-
chloroethylene,  tetrachloroethylene,
chloroform, carbon tetrachloride, chloro-
benzene, dichlorobenzene,  1,2-dichloro-
ethane, and trichloroethane.
  The personal monitor design was to be
similar in size to a radiation badge so that
it could be easily worn. The sorbent
materials in the badge were to be chosen
so that a wide range of toxic organic

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pollutants could be monitored, or if more
selective monitoring was desired, sor-
bents could  be  chosen to preferentially
collect specific  compounds.  Laboratory
tests  and evaluations of the approved
prototype were  to be conducted to
determine overall performance of the unit
in the collection and  analysis of the
pollutants. Testing was to include deter-
mination of sensitivity limits, selectivity,
shelf  life, artifact formation, and other
salient characteristics.

Dosimeter Design
  The passive dosimeter consists of a
stainless steel body, 3.8 cm diameter and
1.1 cm high, which  makes  the device
amenable to thermal desorption, elimi-
nates problems associated with adsorp-
tion of organics into plastic materials, and
provides a rugged, reusable device. The
internal body diameter is reduced to 3.0
cm to provide  a precise containment
volume (~0.4 g) for the porous polymer.
Two sets of stainless steel screens (200
mesh wire)  and perforated plates (28%
open area) are located on each side of the
polymer to confine the polymer and serve
as diffusion  barriers. Friction snap rings
are used to hold the screen and plate tight-
ly against the center of dosimeter body
containing the polymer.
  Application of the passive dosimeter
involves three principal areas of technol-
ogy: diffusion considerations, sorbent
selection, and chemical quantitation of
the sampled compounds.
  The diffusion rate of organic compounds
onto the adsorbent is based on the types of
compounds of interest and their diffusion
constants, the ambient concentration of
the compounds, and the diffusion path
the compounds must take to get to the
adsorbent. Diffusion rates  for several
chlorinated  organic compounds were
calculated as well as defined by laboratory
tests as part of this contract as discussed
later in this report.
  Selection  of  adsorbent materials is
based on the ability of the sorbent to hold
the compounds of interest at the sampling
conditions and  then readily release the
compounds at the desorption conditions
with minimum background interference.
  Chemical  quantification  of  exposed
passive dosimeters  entails  a two-step
procedure.  The first  step  involves the
removal  (desorption)  of collected com-
pound(s) and the second  involves the
determination of  compounds. Typically,
the procedures used are thermal desorp-
tion  and a  gas chromatographic (GC)
procedure with a specific detector (for
example, electron capture or photoioniza-
tion detector) for the  compounds of
interest.

Test Equipment
  Gas standards were generated for
dosimeter  evaluation studies using a
sample generation system employing a
syringe drive of fluids into heated blocks
with three calibrated dilution stages.
  Dosimeters were exposed  to  gas
standards  in one of two exposure
chambers. The first chamber was a 2-liter
borosilicate glass jar fitted with an "0"-
ring-sealed Teflon  lid and multiple
Swagelok® fittings for gas  injection,
sampling, and gas outlet.  Dosimeters
hung in the center of the jar, sampling the
contaminated air during grab type tests.
  The second chamber was a thick-
walled, flanged, borosilicate glass pipe by
which dosimeters could be subjected to a
range of concentrations, temperatures,
humidities, and flow velocities. Sorbent
tubes  were used  to  collect  known
volumes  of sample  to validate  gas
constituent  concentrations  with either
chamber during the tests.

Results

Sorbent Selection
  Porapak R and Tenax GC were evalu-
ated as sorbent materials for use in the
dosimeters,  based  on their  high break-
through volumes and clean background
on the thermal desorption. The Porapak R
sorbent  provided good  results at most
concentration  levels, however, at  low
concentration levels (~1 ppb), recovery of
spiked samples for several chlorinated
compounds was low  (40% to 50%).
Exposure studies using Tenax GC were
more encouraging with recovery efficien-
cies for all components greaterthan 93%.
Tenax GC was subsequently chosen as
the adsorbent material for all future
dosimeter tests.
Performance  Testing
  Initial tests performed on the dosimeter
defined the response of the analytical
systems with compound mass collected
on the dosimeter, the sample concentra-
tion  range,  equivalent sampling rates,
effects of concentration and  exposure
time on dosimeter sampling rates, and
storage of samples.
  A linear response was verified for the
quantity of organic compound on sorbent
and the GC response. This response was
verified for chloroform, carbon tetrachlo-
ride, 1,1,2-trichloroethane, chloroben-
zene, 1,2-dichloroethane, trichloroethy-
lene, and tetrachloroethylene.
  Dosimeter calibration curves were '
developed for  the  low concentration
range (1-50 ppbv) and extended up to
approximately  10 ppmv (see Figure 1).
These curves were established by expo-
sing dosimeters in the sample exposure
chambers for varying times and concen-
trations.
       0    10   20   30   40   50

          Concentration x Time, ppbv-hr

Figure 1.    Example response curve (1,2-
           dichloroethane).


  Sampling  rates for dosimeters were
defined by comparing the dosimeter with
active sorbent sampling  tubes. Simulta-
neous samples were collected by exposing
dosimeters within the chamber and by
withdrawing  gas samples  from sample
ports into the sorbent tubes. Sampling
times were varied between one and four
hours. Two-sided  dosimeter exposure
resulted in equivalent sampling rates of
50  to 60  cc/min.  Averaged equivalent
sampling  rates for one-sided exposure
ranged 25 to 34 cc/min as shown in
Table 1.
  To determine the effect of concentra-
tion and time on dosimeter performance,
triplicate exposures were made at 1-, 2-,
4-, 8-, and 16-hour durations and at con-
centrations of 1, 10, and 100 ppbv. Typi-
cally, there is a decrease  in sampling rate
for the more volatile compounds (i.e.,
chloroform,  1,2-dichloroethane,  and
carbon tetrachloride) at the ppb level as
exposure  time  is increased above ap-
proximately 4 hours.
  Studies to determine the extent in
which compounds  were  lost during
storage was also evaluated.  Exposed
dosimeters were capped with friction-
tight Teflon caps,  sealed in screw-cap

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Table 1 . Average Equivalent Sampling Rates (Single-Faced Sampling)
1,2- Carbon
Chloro- Dichloro- tetra-
form ethane chloride
Pump rate.
cc/min 25.0 26.8 21.8
Std. dev. ±5.0 ±2.9 ±5.2
glass jars, and maintained under ambient Table2. Single-Face
laboratory conditions for twelve days.
Only 10 to 18% decrease was observed
from the 30 ng spike after the 12 days. Compound
pxrrnt for rnrhon tetrachloride which 	 ••
showed a 50% decrease. Chloroform
1 , 2 -Dichloroethane
Sampling Tests Carbon tetrachlor/de
Laboratory validations tests were ^^chlofoefhane
conducted by varying sampling times and Teirachloroethylene
concentrations for single- and dual-faced Chlorobemene


Trichloro-
ethylene

28.3
±1.5
Sampling for One Hour
Concentration
ppbv
Theory Tube
11.6 11.1
13.7 13.7
8.8 10.6
10.4 10.2
10.2 11.1
8.2 8.6
12.1 11.0

1,1.2-
Trichloro-
ethane

27.7
±0.6


Percent
recovery
96
100
120
98
109
105
91

Tetra-
chloro-
ethylene

29.5
±1.9

Concentration,
ppbv
Dosimeter
12.9
13.8
9.7
12.1
12.5
13.7
12.4


Chloro-
bemene

34.3
±4.0

Ratio
..dosimeter/
tube
1.17
1.00
0.91
1.19
1.13
1.59
1.13
tubes were typically used for each test.
Typical results for the validation tests,
shown in Tables 2 and 3, indicate thatthe
dosimeters have  the  ability to identify
compounds and concentrations similarto
the tube  results  or  the expected gas
standard concentrations.
  Small-scale field studies were performed
to provide additional dosimeter validation
information. The  first study conducted
found good recoveries of the laboratory
spikes. In addition, clean dosimeter
blanks were found. Variation in tempera-
tures (80°F to 90°F), relative humidities
(50% to 80%), and wind velocity (5 mph to
25 mph) appeared not to effect results.
  Work station monitoring conducted in a
second field study showed good compari-
sons  between dosimeter and charcoal
and  solid sorbent tubes. As shown in
Table 4, good agreement was shown for
1,2-dichloroethane between the dosimeter
and  charcoal tubes with one exception
(attributed to the fact that the dosimeter
may have been  shielded by protective
clothing).  Table  5 shows additional
results from this study comparing sorbent
tube and dosimeter. In addition, one 5-
hour  sample compared well with the
sum of five consecutive 1-hour samples.


Conclusions and
Recommendations
  A high performance passive dosimeter
was developed  to meet  the rapidly
expanding needs  of ambient  air and
short-term, low-level, personal monitor-
ing.  This  device, employing a porous
polymer as the sorbent medium, satisfies
the stringent requirements  imposed by
ambient air sampling. Detection sensitiv-
ities in the part-per-trillion (ppt) to part-
per-billion (ppb) range have been demon-
Table3.    Dual-Face Sampling Integration Experiment B (1 ppbv - 45 min; 100 ppbv - 15 min)

                        Concentration,                 Concentration.     Ratio
                            ppbv         Percent
Compound
Chloroform
1 ,2-Dichloroethane
Carbon tetrachloride
Trichloroethylene
1, 1 ,2-Trichloroethane
Tetrachloroethylene
Chlorobenzene
Theory
28.0
33.8
21.7
25.4
25.0
20.1
29.7
Tube
26.5
33.6
22.6
24.3
26.7
19.8
32.0
Table 4. 1 ,2-Dichloroethane Sampling with
Parameter
Flow rate, mL/min
Amount collected, ug
Exposure time, hr
Concentration,
fjg/i-
ppmv
Equivalent, mL/min
pump rate
Amount collected, fjg
Exposure time, hr
Concentration,
P9/L
ppmv




1
47.2
81
5.6
5.1
1.3
90
30.0
64.0
5.6
6.3
1.6
recovery
95
99
104
96
107
99
108
Dosimeter
26.7
28.1
24.0
27.7
29.8
28.8
33.9
tube
1.01
0.84
1.06
1.14
1.12
1.43
1.06
Charcoal Tubes and Passive Monitors
Charcoal Tube No.
2
3
46.2 50.2
456 305
5.6 5.6
27.8 18.2
6.9 4.5
Dosimeter No.
91
30.0
277
5.6
25.9
6.4
92
30.0
212
5.6
21.0
5.2
4
49.0
17,865
5.6
1.027
254
93
30.0
1,536
5.6
144.0
35.6
strated for seven halogenated organic
compounds at exposure times of about one
hour. Retention time and detector response
data for twenty-four halogenated com-
pounds were developed to extend com-
pound recognition capabilities. This
simple, inexpensive monitor demonstrates
multicomponent sampling capabilities.
Sampling  performance of the passive
device is comparable to active "pumped"
sampling tubes.  Device  performance is
provided  by the equivalent  pump  rate
characteristics, the high sample recovery
via a thermal desorption process, and the
detection sensitivity  and  specificity
afforded by multiple specific detector GC
analysis.
  While  in-depth  laboratory and field
evaluation studies  have been conducted
with the  monitor,  more  comprehensive

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  field  studies  should be  completed  to
  demonstrate the practical  applicability of
  the monitor to real sampling  problems.
  Hazardous waste sites represent a timely
  sampling  problem that would provide a
  good  practical evaluation of the monitor.
Table 5. Work Station Samp/ing Studies
Mass collected, fjg
Dosimeter sample interval
Compound 1 hr 2 hr 3 hr 4 hr 5 hr
Dosimeter
5-hr
£ exposure
Passive dosimeter
                                           1,2-Dichloroethane
                                           Trichloroethylene
                                           1.1,2-Trichloroethane
                                           Tetrachloroethylene
                                           Chlorobenzene

                                           Pumped tube
0.27
0.58
0.16
0.25
8.4
0.29
0.38
0.48
0.38
18.2
0.24
0.25
.
-
10.4
0.20
0.11
0.38
0.15
8.6
-0.10
0.16
0.48
0.12
6.7
-1.1
1.48
1.50
0.90
51.0
0.67
1.47
0.90
0.66
51.0
1,2-Dichloroethane
Trichloroethylene
1, 1,2-Trichloroethane
Tetrachloroethylene
Chlorobenzene
0.34
0.43
0.49
0.11
7.5

0.14
0.22
-
-
9.6

0.13
0.15
0.59
0.17
5.4

                                               G. W. Wooten, J. E. Strobel, J. V. Pustinger, andC. R. McMillinare with Monsanto
                                                 Company, Dayton, OH 45407.
                                               James D. Mulik is the EPA Project Officer (see below).
                                               The  complete report,  entitled  "Passive Sampling Device for Ambient Air and
                                                 Personal Monitoring," (Order No. PB 84-210 046; Cost: $10,00. subject to
                                                 change) will be available only from:
                                                         National Technical Information Service
                                                         5285 Port Royal Road
                                                        • Springfield. V'A 22161
                                                         Telephone: 703-487-4650
                                                 The EPA Project Officer can be contacted at:
                                                         Environmental Monitoring Systems Laboratory
                                                         U.S. Environmental Protection Agency
                                                         Research Triangle Park, NC 27711
                                                                              •tf U.S. GOVERNMENT PRINTING OFFICE; 1984 — 759-015/7768
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300

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