t
united states
Environmental Protection
Agency
Environmental Sciences Research--
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S2-81-106 Oct 1981
Project Summary
Potential Atmospheric
Carcinogens: Phases 2/3.
Analytical Technique and
Field Evaluation
D. S. West, F. N. Hodgson, J. J. Brooks, D. G. DeAngelis, A. G. Desai, and
C. R. McMillin
A sampling system was developed
to collect 20 significant probable or
possible atmospheric carcinogens
from ambient air. The sampling system
was designed using a combination of
solid sorbent materials consisting of
Tenax-GC, Porapak R, and Ambersorb
XE-340, arranged in series. Air samples
were drawn through this system using
a Nutech Model 221-1A pump.
The system was evaluated in sam-
pling trips to Los Angeles, California;
Niagara Falls, New York; and Houston,
Texas. Analysis of the samples for the
20 selected compounds, as well as
additional broad-scan organic data,
was accomplished using thermal
desorption of the sorbent materials
followed by capillary column gas
chromatography/mass spectrometry
(GC/MS). A sample collected in
Houston was.also analyzed using a
multi-detector capillary column GC
system having a conventional flame
ionization detector, a nitrogenphos-
phorus selective flame ionization
detector, photoionization detector,
and an electron capture detector. A
comparison of GC/MS and multi-
detector GC results was made.
This Project Summary was devel-
oped by EPA's Environmental Sciences
Research Laboratory, Research Tri-
angle 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 general population, particularly
in urban areas, is exposed to a wide
variety of atmospheric pollutants.
Currently, the health hazard posed by
this situation cannot be adequately
defined because of the complexity of the
problem and the lack of sufficient,
reliable data. To accurately assess this
exposure problem, a reliable screening
technique is needed to determine what
substances, at what concentrations, are
present in our ambient atmosphere.
The ability to assess the extent of the
potential health hazard in ambient air
requires at least three things:
(1) Knowledge of the materials that
pose the hazard,
(2) A reliable sampling technique for
collecting these materials, and
(3) Adequate technology for accurate
analyses of these materials.
These three requirements provided
direction for this research program. The
objective of this program was to develop
sampling and analytical techniques for
20 of the most significant, potentially
carcinogenic, atmospheric pollutants
and to demonstrate these techniques
with field tests in selected urban areas.
To fulfill this objective, the program
was divided into three phases that
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roughly paralleled the three years of the
contract. Phase 1 included a background
study, during which time atmospheric
pollutants were prioritized, and 20
compounds were selected to be moni-
tored. In addition, a review of the
carcinogen cofactor literature was
conducted, and isopleths for potential
sampling sites were generated using
the Monsanto Research Corporation
(MRC) Source Assessment Data Base
and the EPA Climatological Dispersion
Model. Results from these first three
activities of Phase 1 have been previ-
ously reported (1).
Phase 2 of the program dealt with
selection and laboratory testing of a
broad-range sampling system, based on
commercially available sorbent materials
and the associated methodology needed
to complete sample analyses. This
phase had much in common with a
companion program (EPA contract 68-
02-2774) aimed at developing a portable
collection system for carcinogens in
ambient air. The related contract
included research on the selection and
evaluation of candidate sorbent mate-
rials, and development of the rationale
for selecting the final combination of
materials to use in a portable sampling
system. Capillary gas chromatography/
mass spectrometry (GC/MS) techniques
were evaluated for use as the "analytical
finish" to the sampling system.
The final phase of the program (Phase
3) involved field evaluation of the
system in actual sampling applications.
Samples were collected in Los Angeles,
Niagara Falls, and Houston using the
sampling system developed during this
program.
An additional study evaluating a
multi-detector capillary GC system for
the analysis of the samples was con-
ducted in conjunction with the Houston
sampling trip. This study was the first
attempt to evaluate the possibility of
using GC with various selective and
nonselective detectors as an alternative
to GC/MS for the analysis of complex
environmental samples.
Summary
The 20 compounds selected for this
study were acrolein, acrylonitrile,
benzene, benzidine, benzo(a)pyrene,
benzyl chloride, carbon tetrachloride,
chrysene, 1,2-dichloropropene, di-(2-
ethylhexyl) phthalate, 1,4-dioxane,
ethylene dibromide, ethylenedichloride,
ethylene oxide, hexachloro-1,3-buta-
diene, pentachlorophenol, styrene.
tetrachloroethylene, toluene-2,4-dia-
mine, and vinyl acetate.
A few general problems were asso-
ciated with the 20 selected compounds.
For example, highly volatile compounds
could not be quantitatively retained on
solid sorbents if the sampling volume
was very high, and nonvolatile com-
pounds, such as benzo(a)pyrene, which
exist in the atmosphere at concentra-
tions lower than volatile compounds,
generally could not be detected analyt-
ically without very high sampling
volumes. Also, reactive compounds,
such as styrene and ethylene oxide,
which tend to polymerize on active
surfaces, were more effectively retained
on sorbents that had relatively more
active surfaces. These conflicts indicated
areas where compromises were required
to develop a single sampling system.
Six commercially available sorbent
materials (Tenax-GC, Porapak N,
Chromosorb 104, Ambersorb XE-340,
SKC, Inc., and activated charcoal) were
evaluated as candidates for the collection
media in this study. The sorbent
properties of these materials were
evaluated using elution profile tech-
niques in a laboratory study. This
involved a matrix of 18 test compounds
representing a wide variety of polarities,
volatilities, and functionalities. Based
on this study, and on other known
sorbent properties (e.g., upper tempera-
ture limit and thermal background), the
following materials were selected for
use in the sampling system:
Tenax GC - The only high temperature
(350°C) adsorbent available that
allows the quantitative thermal de-
sorption of organic compounds with
low volatility.
Porapak R - One of the highest
capacity polymeric adsorbents, with a
reasonable background level (better
than Porapak N) and a range of utility
overlapping with Tenax-GC.
Ambersorb XE-340 - The adsorbent
anticipated to have the least difficulty
with desorption of compounds of
intermediate volatility. Also, Amber-
sorb XE-340 is expected to have
fewer detrimental effects from water
and less reactivity with collected sam-
ples than is charcoal. Ambersorb XE-
340's range of utility leaves the
smallest gap between polymeric and
carbonaceous adsorbents for the
types of compounds collected.
1
These three sorbent materials were
placed in separate glass tubes in series
to complete the sampling system.
Analyses of collected samples involved
thermal desorption of the sorbent tubes,
followed by cryogenic reconcentration
in a capillary trap. The trap was
subsequently heated to introduce the
sample, in the form of a compact "plug",
into a capillary gas chromatograph/
mass spectrometer system. This was
accomplished using either a specially
fabricated inlet system or a commercially
available Nutech Model 320 thermal
desorption system.
The following summarizes the pre-
ferred analytical techniques used for
this project:
Instrument: Hewlett-Packard Model
5985B GC/MS. Column: Methyl
silicone (OV101, SE-30, SP2100 or
equivalent) capillary (fused silica or
glass), 50 m, 0.2-0.25 mm i.d. for
inner diameter.
Temperature Program: Subambient (-
30°C) during tube desorption. Rapid
rise (~30°C/min) to 0°C. More
gradual temperature rise(~8°C/min)
to ~30° below upper temperature^
limit of column. \
Inlet System: Nutech Model 320
thermal desorption system, capillary
direct coupling.
Mass Spectrometer: Scan mode.
As previously mentioned, field tests in
Los Angeles, Niagara Falls, and Houston
were conducted. Only four of the target
compounds (benzene, tetrachloroeth-
ylene, benzyl chloride, and carbon
tetrachloride) were observed in any of
the field samples. Concentrations
ranged from 0.1 to 8 /ug/m3. Numerous
additional compounds were observed
and identified by mass spectrometry.
The system functioned as anticipated,
demonstrating the need, in certain
instances, for additional collection
capacity beyond a single Tenax collector.
However, the degree of breakthrough
into the subsequent Porapak R and
Ambersorb XE-340 tubes varied greatly
with the sampling environment. In the
Los Angeles samples, substantial "pre-
fractionation" was obtained, with
significant amounts of pollutants in
varying ranges collected on each of the
three sorbents. In the Houston samples,
compounds were observed only on the j
Tenax and Porapak tubes. In contrast toJ
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t
the Los Angeles and Houston samples,
the Niagara Falls samples were collected
in an indoor environment. In this
environment, no sample breakthrough
occurred from the Tenax tube to the
Porapak and Ambersorb sorbents.
Although all of the factors involved
have not been fully defined, it is clear
that sampling volume is not the only
factor determining selection of proper
sampling materials. Climatic conditions
such as temperature and humidity, as
well as sample composition, are doubt-
lessly factors as well. For very low
sample volumes, breakthrough from
one sampling material to the next would
not be expected. The continually in-
creasing need for lower detection limits,
however, requires that a large volume of
air be sampled to assure sufficient
material for analyses. Data obtained
during the Niagara Falls sampling show
that, even with a large volume, Tenax
may retain all the organic constituents
under certain conditions. The sample
volume taken at Niagara Falls was
greater than that taken during Houston
sampling and nearly as great as that
taken at Los Angeles. Moreover, loading
of specific compounds of interest was
greater than found at the other locations.
Compound retention on Tenax sorbent
may be affected by factors other than
those mentioned. The evaluation of
these factors are beyond the scope of
this program. These may include selec-
tive displacement effects by other
matrix compounds; interaction with
water whereby an immiscible compound
pair, having a combined vapor pressure
higher than that of either compound (as
in steam distillation), is formed; and
change in the surface characteristics of
the Tenax due to atmospheric constitu-
ents such as ozone or NOX.
A multi-detector capillary gas chro-
matographic [MD(GC) ] system devel-
oped at MRC was used to analyze one of
the samples collected in Houston. In this
system, the effluent from the capillary
chromatographic column is split between
four detectors: a conventional flame
ionization detector (FID), a nitrogen-
phosphorus selective flame ionization
detector (N-PFID), an electron capture
detector (BCD), and a photoionization
detector (PID).
The principle behind the use of such a
system depends upon the detectors'
degree of selectivity. When operated
simultaneously during an analysis, the
ratioing of different detector responses
for compounds "seen" by more than
one detector is permitted. When used in
conjunction with GC retention times,
detector response ratios provide an
additional parameter that greatly im-
proves the confidence of compound
specificity from a GC analysis. The
objective of this work was to conduct a
preliminary investigation of multiple
selective detection and detector re-
sponse ratioing as an alternative
technique to mass spectrometry for the
detection of the compounds of interest.
Results of the MD(GC)2 analyses of
the Houston field samples indicated the
presence of benzene in the Tenax and
Porapak R tubes, as also observed by
capillary GC/MS. Tetrachloroethylene,
determined by (GC)2/MS to also be
present in the Tenax and Porapak R
tubes, was not indicated by the MD(GC)2
analyses. Conversely, carbon tetra-
chloride, acrylonitrile, vinyl acetate,
1,4-dioxane, and ethylene dibromide
were tentatively identified in the field
samples by MD(GC)2.
The detectors of the MD(GC)2 system
are more sensitive than the mass
spectrometer detector, so some of these
tentative identifications might be correct,
yet fall below the detection level of the
mass spectrometer. Alternately, some
of the discrepancies in compound
indentification might be due to a
combination of the limitations for
MD(GC)2 analyses, including shifts in
retention times due to matrix effects.
Results indicated that although
MD(GC)2 is much more selective and
specific than (GC)2 or GC, it cannot
replace GC/MS for the unequivocal
identification of compounds. MD(GC)2
can be used to indicate the possible
presence of selected compounds, al-
though matrix effects and other limita-
tions can imply the presence of com-
pounds not actually present, or the
absence of compounds that are present.
Perhaps a better use for MD(GC)2willbe
to identify various types of compounds
in samples and compile their "total"
amounts. This would provide much
more information than a total chroma-
tographable organics analysis (TCO)
about the composition of an air sample,
and could perhaps be an indicator of
overall air quality in terms of organic
pollutants.
Conclusions
The sampling system operated as
anticipated in field sampling applica-
tions. The need for additional, comple-
mentary sorbent capabilities to those of
Tenax was demonstrated in the Los
Angeles and Houston samples, where
significant amounts of organics were
observed on the subsequent (Porapak
and Ambersorb) tubes. A partial frac-
tionation was also observed on the
various sorbent materials where differ-
ent ranges of compounds (based pri-
marily on volatility) were found. There
appeared to be some influence exerted
by matrix and/or humidity effects on the
amount of breakthrough observed on
the latter sorbents. Niagara Falls
samples were collected in an interior
environment and exhibited little, if any,
compound breakthrough to the Porapak
and Ambersorb materials.
The number of compounds from the
target list of 20 probable or possible
carcinogens observed in actual field
samples was small. The largest number
and highest concentrations of these
targeted compounds were observed in
the Niagara Falls samples.
The analytical methodology was
based primarily on capillary column
GC/MS, using thermal desorption to
recover the sample from the sorbents
for analysis. Samples collected in high
humidity environments (e.g., Houston)
caused particular problems during
analysis due to high concentrations of
water collected on the Porapak and
Ambersorb sorbents. However, it was
found that by changing certain analytical
parameters (e.g., initial GC temperature),
a satisfactory analysis could be per-
formed in these instances.
One sample set from Houston was
also analyzed using a multidetector
capillary GC technique. Results showed
that the multidetector approach offered
advantages over conventional GC in
terms of selectivity and specificity...
However, it cannot replace GC/MS for
unequivocal identification of compounds.
This approach might be applied more
appropriately to assessment of com-
pound types as a more general indicator
of overall air quality.
Recommendations
The following recommendations are
made as the result of the research
conducted during this program:
(1) The sampling system developed
during this project should be
extensively evaluated in other
field sampling situations to further
define its operational capabilities.
(2) The sampling technique employed
should be used primarily as a
"screen" for the presence/
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absence of specific compounds or
for wide-scan evaluation of organic
composition in ambient air, much
as the EPA Priority Pollutant
Protocol is used as a "screen" for
organics in industrial effluents.
(3) Only after the system has been
validated for a specific compound(s)
in a particular air matrix should it
be used to generate quantitative
data.
(4) Validation should use spikes tode-
termine actual recoveries of the
compounds of interest. Stable,iso-
topically-labeled compounds
should be used whenever possible
to allow differentiation between
the spike and the native compound.
(5) When a compound of concern is
identified through the screening
process, confirming studies should
be made to determine if the
compound is real, or is an artifact
of the sampling/analytical tech-
niques.
(6) The multi-detector GC approach
should be further evaluated to
determine its value. This would
include development of computer-
assisted data reduction techniques
to combine the vast amounts of
information and to compare re-
sponses from the various detectors.
D. S. West, F. N. Hodgson. J. J. Brooks, D. G. DeAngelis, A. G. Desai, and C. R.
McMillin are with Monsanto Research Corporation, Dayton, OH 45407.
James Mulik is the EPA Project Officer (see below).
The complete report, entitled "PotentialAtmospheric Carcinogens: Phases 2/3.
Analytical Technique and Field Evaluation," (Order No. PB 82-102476; Cost:
$20.00, 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 Protect ion Agency
Research Triangle Park, NC 27711
1
US GOVERNMENT PRINTING OFFICE; 1981 — 559-017/7413
References
1. McMillin, C. R., L B. Mote, and D. G.
DeAngelis. Potential Atmospheric
Carcinogens, Phase 1: Identification
and Classification. EPA-600/2-80-
015, U.S. Environmental Protection
Agency, Research Triangle Park, NC,
January 1980. 253 pp.
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
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