United States
Environmental Protection
Agency
Environmental Sciences Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S3-83-058 Sept. 1983
Project Summary
Optimization of GC/MS Based
Tenax Collection Method for
Toxic Organics
Barbu Demian and Edo D. Pellizzari
The sampling of vapor-phase organ-
ics in the presence of reactive inor-
ganics using the Tenax GC sampling
cartridge was investigated. To differen-
tiate between pollutants in air and
those formed from in situ artifact reac-
tions, deuterated organics were em-
ployed in both laboratory and field
experiments, and any subsequent arti-
fact products were detected by capil-
lary gas chromatography/mass spec-
trometiy/computer [(GC)VMS/COMP]
techniques. Artifacts produced by Tenax
GC itself and by reactions between
adsorbed species were investigated
using statistical methods.
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 docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
The characterization and measurement
of minute amounts of hazardous com-
pounds in ambient air has, for many years,
been seriously hampered by the lack of
reliable sampling systems. Techniques
have been developed to concentrate or-
ganic vapors from large volumes of atmos-
phere and to transfer the collected vapors
to an analytical system.
There is, however, a paucity of experi-
mental data concerning artifact studies on
collection devices for vapor-phase organ-
ics. Investigators have had a propensity for
accepting the viability of the collection
step prematurely while emphasizing de-
velopment of other steps in analytical
procedures. In fact the literature is replete
with analytical methods for analysis of a few
vapor-phase components in complex mix-
tures using various instrumental methods.
Nonetheless, it should be noted that none
of these procedures can be considered
superior since the collection method is a
common denominator among all the ana-
lytical methods, and appears to be the
weak link
With the elucidation of nitrosamine
presence in ambient air, serious consid-
eration was given to potential artifact for-
mation during collection. In fact, a plethora
of collection methods for nitrosamines
occurred. Artifacts associated with cryo-
genic traps were readily apparent,and
modifications ensued which eventually
lead to using a sorbent cartridge impreg-
nated with sulfamic acid to inhibit the in
situ nitrosation of secondary amines.
An approach to detecting, identifying,
and quantifying halogenated hydrocar-
bons in ambient air has involved using a
Tenax GC cartridge combined with high
resolution gas chromatography/mass spec-
trometry/computer [(GC)2/MS/COMP]
analysis. The primary concern was to use a
Tenax GC sorbent that has been previously
employed for collecting vapor-phase or-
ganics in ambient air. Since the Tenax GC
cartridge may concentrate reactive com-
pounds from an atmosphere containing,
for example, ozone (03), nitrogen oxides
(NOX), molecular halogen such as chlorine
(CI2) and bromine (Br2), in situ formation
of artifact products may occur, even though
inorganic gases do not appreciably ac-
cumulate on the sorbent. Preliminary
studies indicated that a more in-depth
study was needed.
The objectives of this research program
were: (a) to examine the potentiaIly trou ble-
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some chemical group types that exhibit
reactivity with the commonly occurring
inorganic gases in ambient air; (b) to
conduct a series of controlled laboratory
experiments to determine the extent, if
any, of artifact problems associated with
the direct interaction of these inorganic
gases with Tenax GC itself; (c) to evaluate
the artifact problems, if any, associated
with organics on Tenax GC in the presence
of atmospheric concentrations of inorganic
gases; (d) to develop a way to minimize
potential artifacts if they exist; and (e) to
evaluate and apply potential corrective
measures that minimize artifact production
under field sampling conditions.
Effects of Ozone and Nitrogen
Oxides
A 23 factorial experiment was planned
to assess the ozone/nitric oxides/humid-
ified air (03/NOX/H20) combination ef-
fect on Tenax. For quantitative analysis,
the gas chromatographic system was cali-
brated with external standards. The identity
of the major Tenax GC decomposition
products was established by GC/MS
methods.
Clean, "virgin" Tenax GC cartridges
were exposed to air containing 03/NOX/
H20, and pertinent information regarding
Tenax GC cartridge exposure was obtained.
The most important Tenax GC decom-
position products were benzaldehyde,
acetophenone, and phenol, indicating
ozonolysis to be the polymer's major
chemical reaction. After breakdown of the
polymer backbone, further reactions of the
primary degradation products lead to the
relatively stable compounds actually de-
tected. This result corroborates the many
reports citing that interaction with atmos-
pheric O3 is the main degradative mech-
anism of polymeric materials.
Humidity had a strong effect This is
important since more attention should be
given to artifact formation from Tenax GC
when sampling air with a high relative
humidity.
The ozone concentration and N02 con-
centration behaved additively. The three
major decomposition products were found
in easily detectable and.dosable quantities,
even in "clean" cartridges. It appears,
however, that analysis for any of the three
major decomposition products at levels
below 100 ng/L with Tenax GC sampling
is not possible without taking special
precautions.
Effects of Sulfur Oxides
Tenax GC cartridges were exposed to
30 L of air containing 03, sulfur oxides
(SOX), and NOX at different humidity levels.
The major Tenax GC decomposition prod-
ucts were confirmed but no compounds
that could identify the presence of SOX
could be detected.
Effects of Chlorine
Tenax GC cartridges were exposed to
03, CI2, and humidified air. The same
major decomposition products were ob-
served.
Effects of Tenax GC Aging
Substantially lower levels of decompo-
sition products were found in sampled air
containing SOX and CI2. This effect was
not related to the nature of the reactive
inorganic gas (in all experiments 03 was
present, the main factor in polymer degra-
dation), but to the history of the Tenax GC
cartridge.
Recycled Tenax GC cartridges were used
in the SOX and CI2 series. The hypothesis
that cartridge history was the main factor
in the total quantity of degradation prod-
ucts was tested using the same cartridge
exposed to 30 L of air in 30 min, with 100
ppb 03, 1 50 ppb NOX, and 60% humidi-
fied air. The quantities of degradation
products decreased by an order of magni-
tude after five analysis cycles.
Artifact Products from
Adsorbed Compound
Reactions
Tenax GC cartridges (sorbent bed di-
mensions, 60 mm length x 13 diameter)
were loaded with d10-cyclohexene or d5-
ethanol. For quantitation, 2-fluorobiphenyl
was used as an internal standard. Stand-
ard solutions of d^-cyclohexene and 2-
fluorobiphenyl were prepared by weighing
and dissolving in pure methanol.
The loaded cartridges were exposed to
an air flow containing inorganic gases in
the concentrations listed below (inorganic
gases are potential generators of artifacts
by reaction with the adsorbed d^-cyclo-
hexene:
CI2 maximum concentration,
564 ppb
03 maximum concentration,
1,000 ppb
N0/N02 maximum concentration,
500 ppb
S02/S03 maximum concentration,
400 ppb
humidified 50% at 25°C
air
For the low concentration range of reac-
tive inorganic components in the sampled
air, no deuterated cyclohexene product
was detected. At higher chlorine concen-
trations, d10-dichlorocyclohexane was
found. A nondeuterated dichlorocyclc-
hexane was also identified in the same
samples, probably from CI2 reacting with
cyclohexene (a contaminant). Deuterated
compounds derived from d5-ethanol and
contaminants typical for Tenax GC were
identified as early eluting compounds (i.e.,
contaminants). The potential oxidation
products - acetaldehyde and acetic acid -
were not detected during GC/MS analysis.
Artifact Inhibition with
Impregnated Filters
A series of filters was impregnated with
various reducing agents for03. The sodium
thiosulfate impregnated glass fiber filters
appear to be the best in quenching ozone.
Relatively good - but less spectacular -
results were obtained for N02 quenching.
The inclusion of sodium lauryl sulfate in
the impregnating solution was proposed
with the view that a surfactant would
lower the solution's surface tension and
allow a better wetting of the filter, thus
improving overall performance. This be-
havior was observed for the hydrophobic
Teflon filters, which cannot be impreg-
nated uniformly with reducing agents in
the absence of surfactants.
Studies on Artifact Problems
Under Field Sampling
Conditions
The results from laboratory experiments
suggested two types of filters for best
overall performance: glass fiber filters im-
pregnated with sodium thiosulfate and
Teflon filters impregnated with sodium
thiosulfate/sodium lauryl sulfate. The
major objective in designing the field ex-
periments was to test these two types of
filters for inhibition of Tenax GC decom-
position and for reduction of in situ reac-
tions of adsorbed compounds.
The deuterated compounds selected
and the possible artifactual reactions were
as follows:
(1) d10-cyclohexene: chlorination and
oxidation;
(2) d6-benzene: aromatic substitution
and oxidation; and
(3) d8-dioxane: oxidation (peroxide for-
mation).
In conducting field experiments, two
sorbent cartridges were run parallel. One
cartridge was protected by an impreg-
nated filter and the other cartridge by an
unimpregnated filter.
The objectives using (GC)2/MS/COMP
analysis were as follows:
(1) assess the recovery of deuterated
compounds from exposed cartridges;
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(2) identify reaction products of deu-
terated compounds; and
(3) quantify adsorbed volatile organic
compounds, i.e., determine the trends
in the quantities found, relative to
using impregnated filters.
The statistical analysts of aromatic com-
pound data was restricted to the higher
concentration range, i.e., more than 300
ng benzene/cartridge, in order to avoid
unaccountable contamination effects. Only
for toluene was a positive difference statis-
tically significant. The loss of the aromatic
compounds by further reaction of adsorbed
species was, therefore, negligible at the
level of sensitivity of the analytical method.
The following were excluded from the
statistical analysis of the halogenated
compound data:
(1)1,2-dichloroethane, due to the high
concentration level in air;
(2) 1,2-dibromoethane, since it is prac-
tically absent; and
(3) carbon tetrachloride and dichloro-
benzene, which are present at very
low concentrations.
The statistical analysis was restricted to
the higher concentration range for the
halogenated compounds as well (same
Tenax cartridge as for aromatics).
The collection of chloroform and tn-
chloroethane data was erratic and, there-
fore, useless in these experiments. For
trichloroethylene, a positive difference
was statistically significant fourtimes, and
for tetrachloroethylene, only once. Again,
there was some evidence that the impreg-
nated filter was preventing sample loss by
further reaction of the adsorbed compound
if it was relatively reactive.
It was highly significant that the evi-
dence for sample loss by artifact reaction
was positive only for unsaturated com-
pounds (cyclohexene, trichloroethylene,
tetrachloroethylene), which were more re-
active toward 03.
The phenol data were also unreliable.
Due to their strong acidic nature, phenol
and acetic acid are subject to serious
limitations in trace analysis by chromato-
graphic methods, the best deactivated
capillaries bind significant quantities ir-
reversibly.
Conclusions and
Recommendations
(2) The tr-h'-i f.v^oit, uetcrmining the
qnantities of artifacts generated were,
in order of decreasing importance, as
follows:
(a) 03 concentration of sampled air;
(b) Tenax cartridge age;
(••) humidity of sampled air;
(d) "Concentration of NOX; and
(e) concentrations of other reactive
comp unds (SOX, CI2).
(3) Artifact i -••ot'ons of adsorbed species
were fount, to be:
(a) relativeK unimportant for aromatic-;
and saturated halogenated com-
pounds; and
(b) significant for more reactive com-
pounds, e.c,., unsaturated com-
pounds such as i'ichloroethylene
and tetrachloroethyltirit.
(4) Sodium thiosulfate impregnated fil-
ters were found to be:
(a) effective in artifacts generated by
Tenax GC itself; and
(b) effective in reducing artifact reac-
tions of reactive adsorbed species.
Use of sodium thiosulfate impregnated
glass fiber filters for sampling with Tenax
GC cartridges is strongly recommended.
Based on the results of laboratory and
field experiments on artifact formation,
three important recommendations are
n-.ade:
(1) Sodium thiosulfate impregnated
glass fiber filters should be used,
with an expected improvement in
these characteristics:
(a) collection efficiency of com-
pounds reactive to 03 (e.g., un-
saturated compounds); and
(b) Tenax GC sorbent stability, which
will result in fewer artifact prod-
ucts.
(2) Selection of the sampling volume
must consider the air's humidity
(80 to 100% relative humidity),
thereby avoiding excessive artifact
formation, and, at the same time,
early breakthrough for the more
volatile components sampled.
(3) If the quantities found for benzalde-
hyde, acetophenone, and phenol are
more than 1,000 no/cartridge,
quantitation for these compounds
can be conducted.
Barbu Demian and Edo D. Pellizzari are with the Research Triangle Institute,
Research Triangle Park, NC 27709.
Kenneth Krost is the EPA Project Officer (see below).
The complete report, entitled "Optimization of GC/MS Based Tenax Collection
Method for Toxic Organics," (Order No. PB 83-229 476; Cost: $ 13.00, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
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 27717
*US GOVERNNtNT PRINTING OFFICE 1983-659-017/7189
(1) The main artifacts produced from
Tenax GC were benzaldehyde, aceto-
phenone, phenol, a-hydroxyacetophe-
none, acetic acid, and ethylene oxide.
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