United States
Environmental Protection
Agency
Atmospheric Research and
Exposure Assessment Laboratory
Research Triangte Park NC 27711
Research and Development
EPA/600/S3-90/097 Feb. 1991
EPA Project Summary
Gas Chromatography/
Matrix Isolation-Infrared
Spectrometry for Air
Sample Analysis
Jeffrey W. Childers
This report describes the applica-
tion of gas chromatography/matrix iso-
lation-infrared (GC/MI-IR) spectrometry
to the analysis of several environmen-
tal air sample extracts. Samples that
were analyzed include extracts from
woodsmoke-impacted air, XAD-2 blanks,
indoor air, and carpet samples. The
emphasis of this report is on the use of
GC/MI-IR to identify semivolatile organic
compounds in these extracts. The
complementarity of GC/MI-IR spectrom-
etry and conventional electron-impact
ionization gas chromatography/mass
spectrometry (El-GC/JWS) is illustrated.
The capability of GC/MI-IR to discrimi-
nate between isomeric compounds that
are difficult to separate chromato-
graphically and to distinguish by
EI-GC/MS is demonstrated. Preliminary
results regarding the potential of
GC/MI-IR spectrometry for the quanti-
tative analysis of polycyclic aromatic
hydrocarbons in air sample extracts are
presented. Problem areas and modifi-
cations of a commercial GC/MI-IR sys-
tem are discussed.
This Project Summary was devel-
oped by EPA's Atmospheric Research
and Exposure Assessment Laboratory,
Research Triangle Park, NC, to an-
nounce 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 capabilities of gas chromatogra-
phy/matrix isolation-infrared (GC/MI-IR)
spectrometry for characterizing semivola-
tile organic compounds (SVOCs) in envi-
ronmental air sample extracts were
evaluated in this study. Since the devel-
opment of GC/MI-IR spectrometry, several
applications of the technique to the analy-
sis of difficult samples have been reported
in the literature. Many of these applications
have been to environmental and health-
related problems. Although several early
reports of data obtained by GC/MI-IR dealt
with the examination of the MI-IR spectra
of environmentally important compounds,
these studies were not direct applications
of the technique to actual environmental
samples. Thus, the capabilities, uses, and
limits of GC/MI-IR for the analysis of real-
world environmental samples must be de-
termined.
In GC/MI-IR spectrometry, the effluent
from the GC is trapped in an inert matrix as
it is deposited on the surface of a rotating,
gold-plated, cryogenic disk. The eiuates
remain frozen indefinitely on the disk and
are analyzed by MI-IR spectrometry after
the GC run is completed. Cryogenic trap-
ping techniques, such as GC/MI-IR, offer
several advantages over the more con-
ventional, light-pipe-based GC/iR systems.
The principal advantage is an increase in
sensitivity. The increase in sensitivity is
realized because the eluate is concen-
trated in a small cross-sectional area on
the cryogenic disk, and most of each GC
peak is interrogated by the IR beam during
each scan. Also, because the eluate is
frozen on the disk indefinitely, signal-av-
eraging is allowed on any GC peak to
increase the signal-to-noise ratio to the
level necessary to obtain an identifiable
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spectrum. Band broadening due to mo-
lecular rotation and intermolecular interac-
tions is also minimized because the eluate
is trapped in an inert matrix at a very low
temperature. This results in sharper IR
bands, which affords greater molecular
specificity to aid in identifying components
in complex mixtures and differentiating
between isomers and other closely related
compounds. In cryogenic-trapping GC/IR
systems, the separation and detection of
eluates are independent steps. Therefore,
the chromatography and the spectrometry
can be optimized without compromising
one or the other.
In this report, we demonstrate the ap-
plication of GC/MI-IR spectrometry to the
analysis of extracts of woodsmoke-im-
pacted air, indoor air, and carpet samples.
Samples that were analyzed include the
following:
• extracts of air samples collected on
XAD-2 cartridges during afield study
in a woodsmoke-impacted residen-
tial area
extracts of XAD-2 blank cartridges
that elicited an abnormally high bio-
assay response
• composite samples collected on
quartz-fiber filter from woodsmoke-
and mobile source-impacted areas
* a nhro-substHuted polycyclic aromatic
hydrocarbon (PAH) fraction of a
pooled mobile source air sample and
selected nitro-PAH standards
• selected polyurethane foam (PUF)
and filter extracts from a pilot resi-
dential indoor air study
extracts from air samples collected
on XAD-2 cartridges in a complaint
building
• extracts from selected carpet samples
The primary focus of the report is on
the evaluation of the capabilities of GC/MI-
IR for identifying specific SVOCs in com-
plex environmental air sample extracts.
The complementarity of GC/MI-IR and GC/
mass spectrometry (MS) for the analysis of
environmental samples is also illustrated.
Most of the results described in this report
pertain to the qualitative identification of
unknowns in various sample extracts. We
also present preliminary results regarding
the potential of GC/MI-IR for quantitative
analyses and discuss problems encoun-
tered with the GC/MI-IR system.
Procedure
All GC/MI-IR data were collected on a
Mattson Instruments (Madison, Wl)
Cryolect system. This system consists of a
Mattson Instruments Sirius 100 Fourier
transform IR spectrometer and Starlab data
system, a Hewlett-Packard (HP) 5890A
capillary GC, and a Mattson Instruments
matrix-isolation cryogenic module. In the
Cryolect system, the effluent of the analyti-
cal GC column is split, with 20% directed
to a flame ionization detector (FID); the
remaining 80% is directed through an open-
spirt cross and then through a heated,
fused-silica transfer line to the cryogenic
disk. The cryogenic disk is housed in an
evacuated chamber and is maintained at
14 K during deposition and spectral analy-
sis of the sample extract. The MI-IR spec-
tra were obtained by coadding 128 scans
at a nominal resolution of 4 cm'1.
The GC/MS results were obtained on
an HP 5970B mass selective detector
(MSD) interfaced to an HP 5980A capillary
GC. Similar chromatographic conditions,
including on-column injection, a (95%)-
dimethyl-(5%)-diphenyl pplysiloxane capil-
lary column, and identical temperature
programs, were used for both GC/MI-IR
and GC/MS analyses.
Results and Discussion
Extracts of XAD-2 Cartridges from
a Field Study in a Woodsmoke-
impacted Residential Area
Representative extracts of air samples
collected onto XAD-2 cartridges during a
field study designed to determine the im-
pact of residential wood combustion on
relatively simple airsheds were analyzed
by GC/MI-IR and GC/MS. We analyzed
extracts of air samples that were collected
outdoors at night, outdoors during the day,
indoors at residences with a wood-fired
stove, and indoors at'residences without a
wood-fired stove. The chromatographic
profiles of the different samples were
qualitatively very similar, with each extract
containing the same major components.
Preliminary GC/MS analyses indicated that
the major components of each extract were
alkylbenzenes, including toluene, ethyl-
benzene, xylenes, ethyltoluenes, and
trimethylbenzenes. Specific positional iso-
mers could not be distinguished by
GC/MS but were identified by GC/MI-IR.
The MI-IR spectra of alkylbenzenes exhibit
characteristic strong absorption bands be-
tween 1000 and 650 cnr1, which are due to
the vibrational mode of the C-H out-of-
plane deformation. The specific frequen-
cies of these bands are determined by the
position of the substituents on the ring and
the number of adjacent hydrogen atoms
remaining on the ring. Thus, the GC/MI-IR
analysis of the XAD-2 extracts of the
woodsmoke-impacted air enabled specific
isomers, such as 3- and 4-ethyltoluene, to
be identified even if they were not sepa-
rated chromatographically (see Figure 1).
In addition to the alkylbenzenes, guaiacol
(a potential woodsmoke tracer) was identi-
fied in an outdoor-nighttime residential air
sample but was not detected in the indoor
or daytime samples. Compounds identified
in the indoor air samples, but not the out-
door samples, included d-limonene, 1,4-
dichlorobenzene, normal aldehydes, and
several alkanes.
Extracts of XAD-2 Blank Cartridges
that Elicited an Abnormally High
Bioassay Response
Two concentrated extracts of XAD-2
blank cartridges that yielded abnormally
high bioassay responses were analyzed
by GC/MI-IR and GC/MS. Both extracts
contained 2-ethyl-1-hexanol, C4-ben-
zenes, acetophenone, substituted aceto-
phenones, an ethylstyrene, a silane, an
unidentified aldehyde, naphthalene, and
several esters, phthalates, and alkanes.
One extract also contained two major com-
ponents that were not detected in the other.
One of these components was identified
as 4-chlorophenylsulfone, and the other
was tentatively identified as triphenylphos-
phine. No compounds were identified in
the blank extracts that would be expected
to contribute significantly to the mutage-
nic'rty of these extracts.
Quartz-Fiber Filter Composites
from Woodsmoke- and Mobile
Source-Impacted Areas
Two nonpolar fractions of ambient filter
composite extracts, a woodsmoke com-
posite and a mobile source composite,
were analyzed by GC/MI-IR and GC/MS.
The chromatographic profiles of each ex-
tract were similar; both contained com-
pounds associated'with woodsmoke, such
as 1-methyl-7-isopropylphenanthrene (re-
tene) and the methyl ester of dehydroabietic
acid, in addition to a series of alkanes and
siloxanes and a large amount of back-
ground material. In spite of the large amount
of background material present in the
chromatogram, several PAH compounds,
including fluoranthene, pyrene, 1-
methylpyrene, and 5-methylchryse.ne, were
identified in both extracts. By using
GC/MI-IR, the presence of coeluting iso-
meric and closely related PAHs in the
composite extracts was confirmed. For ex-
ample, an unambiguous distinction between
cyclopenta[c,d]pyrene and benz[a]anthra-
cene was made, and the. chrysene-
triphenylene isomer pair was distinguished
(see Figure 2).
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1600
1400
1200 1000
Wavenumber
800
Figure 1. MI-1R spectra of (A) a component from an extract of an XAD-2 cartridge collected during a field study in a woodsmoke-impacted
residential area, (B) 3-ethyltoluene reference standard, and (C) 4-ethyltoluene reference standard.
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1600
r r
1400 1200
Wavenumber
1000
800
Figure 2. Ml-IR spectra of (A) a component of a filter composite extract from woodsmoke- and mobile-source-impacted areas, (B) chrysene
reference standard, and (C) triphenylene reference standard. , . ,
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A Nitro-PAH Fraction and
Selected Nitro-PAH Standards
A nitro-PAH fraction of a pooled mo-
bile source air sample extract was ana-
lyzed by GC/MI-IR. Reference MI-IR
spectra of 1-nitropyrene, 2-nitrofluor-
anthene, 2-nitropyrene, and 6-nitro-
benzo[ajpyrene were also acquired.
Although high-quality MI-IR reference
spectra of the standard compounds could
be obtained, no target nitro-PAH were
detected in the fractionated sample ex-
tract. The levels of nitro-PAHs in this frac-
tion were estimated to be less than 100
pg/uL, which is below the detection limits
of the GC/MI-IR system for these com-
pounds. The reference spectra obtained
on the GC/MI-IR system were compa-
rable to MI-IR spectra of nitro-PAHs in the
literature that were obtained under con-
ventional slow-spray-on MI-IR conditions.
Selected PUF and Filter Extracts
from a Pilot Residential Indoor Air
Study
Selected PUF and quartz-fiber filter
extracts collected during a pilot residen-
tial indoor air study were analyzed by GC/
MI-IR and GC/MS. The results from these
analyses illustrated the difference in sen-
sitivity and selectivity of GC/MI-IR and
GC/MS for different chemical classes. For
instance, the GC/MI-IR analysis showed
the presence of a number of carbonyl-
containing compounds, such as esters
and carboxylic acids, whereas the scan-
ning GC/MSD results were dominated by
a series of lorig-chain, alkyl-substituted
benzenes. The three-ring PAH isomers,
phenanthrene and anthracene, were dis-
tinguished by GC/MI-IR in the presence
of background material in the chromato-
gram of a PUF extract. Nicotine and
tetraethylene glycol dimethylether were
identified as the major components in an
extract of SVOCs collected on a quartz-
fiber filter in a smoker's home.
Extracts from XAD-2 Cartridges
Collected in a Complaint Building
The GC/MI-IR and GC/MS systems
were used to analyze an extract of an
XAD-2 cartridge collected from a room in
an office complex during an episode of
health-related complaints by employees.
The extracts contained several n-al-
kanes, branched alkanes, and alkylated
benzenes. Other major components of
the extract that were identified included 2-
butoxyethanol, benzaldehyde, 1,4-dichlo-
robenzene, an n-aldehyde, a-terpineol,
4-phenylcyclohexene, and two 2,2,4-
trimethylpentane(1,3)diol isomers. The
presence of 4-phenylcyclohexene, a by-
product of the carpet manufacturing pro-
-cess and a suspected irritant associated
with the characteristic odor of new carpet,
prompted an investigation into the SVOCs
and nonvolatile organic compounds associ-
ated with new carpet.
Extracts from Selected Carpet
Samples
Several carpet samples were Soxhlet-
extracted in methylene chloride, concen-
trated, and then analyzed by GC/MI-IR and
GC/MS. The GC/MI-IR analyses were used
primarily to confirm tentative identifications
made by GC/MS analyses. In addition, the
unique features of MI-IR spectra, such as
split carbonyl peaks and sharp O-H stretch-
ing bands, that are not found in condensed-
phase or vapor-phase IR spectra aided in
identifying components in the extracts.
In the analysis of these carpet samples,
the GC/MI-IR results were used to confirm
an error in a commercial mass spectral data
base and to distinguish between SVOCs
that have very similar mass spectra but
signficantly different MI-IR spectra, such as
6-aminohexanoic acid and e-caprolactam.
The MI-IR spectrum of e-caprolactam ex-
hibits a split in the carbonyl absorption band,
which would normally indicate the presence
of more than one carbonyl moiety (see Fig-
ure 3). However, e-caprolactam has only one
carbonyl group. A search of the literature
revealed that the MI-IR spectra of lactams,
as well as many other compounds that
contain a carbonyl group, can exhibit multiple
carbonyl absorption bands. In the case of
lactams, this multiplicity is attributed to the
isolation of discrete conformers in the matrix.
The MI-IR spectra of several phenols and
diols identified in the carpet extracts exhib-
ited sharp O-H stretching bands, which indi-
cated the lack of intermolecular hydrogen
bonding under the GC/MI-IR deposition
conditions. The GC/MI-IR results were also
used to identify background material, which .
was originally assigned to column bleed by
interpretation of the GC/MS results, as an
isocyanate.
Preliminary Investigation of the
Quantitative Capabilities of GC/MI-
IR
We have performed a preliminary inves-
tigation of the quantitative capabilities of
GC/MI-IR spectrometry for the determina-
tion of target PAHs in environmental air
sample extracts. Our initial goals were to
determine the repeatability, the dynamic
range, and the detection limits of the GC/
MI-IR system for PAH compounds. To de-
termine the repeatability of the GC/MI-IR
measurement, we analyzed replicate in-
jections of a 10-ng/u.L standard PAH mix-
ture containing 10-ng/u.L of 1-methyl-
benz[a]anthracene as an internal standard.
The MI-IR absorbance maximum of the
analyte was normalized to the MI-IR ab-
sorbance maximum of the internal stan-
dard. Likewise, the FID peak area was
normalized to the FID peak area of the
internal standard. The average relative
standard deviation of six replicate analy-
ses was approximately 20% for the nor-
malized MI-IR absorbance and on the order
of 1% for the normalized FID peak areas.
Because of the poor repeatability of the
GC/MI-IR measurements, the dynamic
range and the detection limits of the sys-
tem for PAHs could not be determined.
Fundamental experiments are currently
underway to determine the sources of er-
ror in GC/MI-IR quantitative analyses.
Conclusions and
Recommendations
In general, we have found GC/MI-IR
spectrometry to be very useful for identify-
ing SVOCs in a variety of environmental
air sample extracts. In many cases the
information obtained from the GC/MI-IR
analyses supported 'tentative ,;.•«;,ideations
made from preliminary GC/MS analyses.
In cases where a definitive identification
could not be made, the GC/MI-IR results
often supplied enough information for a
general compound classification to be
made. In addition, the GC/MI-IR analysis
often revealed unique information that could
not easily by obtained by other existing
analytical techniques. In particular, we have
demonstrated the capabilities of GC/MI-IR
to discriminate between compounds such
as alkylbenzene positional isomers and
PAH isomers, which are difficult to sepa-
rate chromatographically and to distinguish
by conventional GC/MS. Although absolute
detection limits have not been determined,
we have found that the minimum quanti-
ties of analyte needed for identifications by
GC/MI-IR are very similar to those required
by GC/MS in the scan mode. In practical
terms, if a compound can be detected by
scanning GC/MS, it is likely that an identifi-
able MI-IR spectrum of that component
can be obtained on the GC/MI-IR system.
We recommend investigating the po-
tential of interfacing the GC/MI-IR system
to an MSD system to fully exploit the
complementarity of the two techniques.
We also recommend further evaluation of
the quantitative capabilities of the GC/MI-
IR technique and a thorough investigation
to elucidate the sources of error in GC/MI-
IR quantitative measurements.
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B
i i i i I I
4000 3500
i i | r i i i | i
3000 2500 2000
Wavenumber
1500 1000
Figure 3. MI-IR spectra of (A) a component of a carpet extract and (B) e-caprotactam reference standard.
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Jeffrey W. Childersis with NSI Technology Services Corporation, Environmental
Sciences, Research Triangle Park, NC 27709,
Nancy K. Wilson is the EPA Project Officer (see below).
The complete report, entitled "Gas Chromatography/Matrix Isolation-Infrared Spectrom-
etry For Air Sample Analysis," (Order No. PB91-136317/AS; Cost: $23.00, 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:
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
BULK RATE
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Official Business
Penalty for Private Use $300
EPA/600/S3-90/097
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