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Problems with tenax-GC for environmental sampling
Chemosphere No. 6, pp 303 - 308, 1977.
Pergamon Press.
Printed in Great Britain.
PROBLEMS WITH TENAX-GC FOR ENVIRONMENTAL SAMPLING R. D. Vick,
J. J. Richard,
Dept. of Chemistry,
H. J. Svec and G. A. Junk Energy and Mineral
Resources Research Institute and Ames Laboratory - U.S.E.R.D.A. lows State University,
Ames,
lows
50011 U.S.A.
(Received in The Netherlands 5 April i~7; accepted for publication I] April 1977) Tenax-GC,
a diphenylphenylene
oxide polymer,
has been used widely
as a collection medium for trace organic pollutants
in atmospheres
because of its desirable accumulation and desorption characteristics. Only minor problems have been reported with nitromethane l, sulfur
compounds 2, a c e t i c
a c i d 3, a c e t o p h e n o n e 4 and b e n z a l d e h y d e 4.
The
possible reported difficulties with extraneous gas chromatograph
(GC)
peaks 5 and undefined background levels 3 can be resolved by proper conditioning and the elimination of inorganic gases such as chlorine. The temperature
stability of Tenax has prompted many investigators
to use thermal desorption for the direct transfer of the collected material to their GC systems I-6. sensitivity,
Although this approach gives high
it does not allow for replicate analyses from a single
sample accumulation.
When replicate analyses are necessary,
a solvent
must be used to elute the material collected on the polymer 3'7'8.
The
solubility of Tenax in many solvents used for elution may cause analytical problems as discussed in this report. A second short-coming of Tenax is related to its instability under certain conditions. piing,
as
has
When used as a sorbent for stack gas sam-
been suggested in several reports 3'5'7'8,
the 2,6-diphenyl
p-phenylene oxide polymer can react to form significant amounts of
3o3
304
~o. 6
2, 6-diphenyl-p-quinone
(2, 6-DPQ). MATERIALS
Apparatus.
A Perkin-Elmer
flame ionization collection, electron
detectors
3920 gas chromatograph
equipped with dual
(FID) and an effluent
splitter for fraction
and a Tracor 550 gas chromatograph
capture detector
Standards. mercially
quinone,
spectrometer
A duPont
(GC-MS) was used for the
analyses.
A primary reference so it was synthesized
the procedure
with a 63Ni
(ECD) were used for the GC analyses.
21-490-1 gas chromatograph-mass mass spectral
equipped
of Finkbeiner
2,5-DPQ
sample of 2,6-DPQ was unavailable from Tenax-GC
and Toothaker 9.
(98%, Aldrich Chemical
by vacuum sublimation
Co.,
and recrystallization,
com-
(Alltech Associates) A commercially Inc.),
by
available
after purification
was used as a secondary
standard. METHODS AND RESULTS Tenax-GC
Solubility.
The solubility
elution solvents was measured These were determined
of Tenax in several commonly used
and the values are listed in Table i.
from gravimetric
differences
after equilibration
of 50 mg of Tenax in 3 ml of each solvent at room temperature
for four
days. The characteristics
of the Tenax remaining
tion may be altered thus limiting solvent containing
its re-use,
after partial
and injection of the
dissolved polymer may be detrimental Table I.
Solubility
Solvent methylene
of Tenax-GC. mg/ml
chloride
dissolu-
16.3
tetrahydrofuran
14.4
benzene
12.2
diethylether
0.3
pentane
0.0
to GC systems.
No. 6
]o5
I d e n t i f i c a t i o n of 2,6-DPQ.
The m a j o r component
of a stack gas extract was f r a c t i o n - c o l l e c t e d a c c o r d i n g to the p r o c e d u r e of Witiak et.al. I0.
in the FID c h r o m a t o g r a m
via the effluent
splitter
The f r a c t i o n - c o l l e c t e d
compound was then sampled by direct insertion to acquire the mass spectral data for i n t e r p r e t a t i o n and eventual 2,6-DPQ.
i d e n t i f i c a t i o n as the
This component was observed w h e n e v e r Tenax was used for
stack gas sampling. Polymer Decomposition.
Parallel
another high temperature polymer,
sampling of stack gas on Tenax and A m b e r l i t e XE-3~O
(Rohm and Haas Co.),
d e m o n s t r a t e d that the quinone was not a component of the stack emission. Samples were collected s i m u l t a n e o u s l y on both polymers by splitting the flow from a single stack probe. graphed with ECD detection.
A peak c o r r e s p o n d i n g to 2,6-DPQ was observed
from the Tenax c o l l e c t i o n only. was shown to be an effective
The separate extracts were chromato-
In a separate test,
Amberlite XE-340
sorption m e d i u m for the analysis of gaseous
2, 5-DPQ. A small amount of the 2,6-DPQ was also p r o d u c e d by the o x i d a t i o n of I0 mg of Tenax using PbO 2 in a c h l o r o b e n z e n e - b e n z o i c A l t h o u g h the reaction conditions stack gas sampling,
acid solution 9.
do not represent those existing during
the results do demonstrate
that Tenax can be oxi-
dized to the quinone in an acid environment. An attempt to produce the quinone by s i m u l a t i n g the stack conditions was unsuccessful.
In this case air was drawn through boiling
HsSO 4 and t r a n s f e r r e d via heated lines to a column of Tenax.
The
extract from this experiment gave no GC peak at the retention time expected for 2,6-DPQ. Losses of DPQ.
Losses due to adsorption,
light and sulfur effects were
m e a s u r e d using solutions of 2,6-DPQ and an internal standard,
n-docosane
(C22). A d s o r p t i o n losses of DPQ were indicated by the n o n - l i n e a r i t y and the inverse r e l a t i o n s h i p of the detector response to contact with metal ss shown in Figure I.
506
No. 6
I
I
I
1.0
B
Fi~. I. FID response of 2,6-diphenyl-p-quinone (DPQ) in hexane relative to C22 internal standard. A. all glass system B. combination glass-metal system C. all metal system
~0.5 hi >
I-.J W n~
q
-C
O.O I 1.0
I 2.0
MICROGRAMS
I
3.0
DPQ
The loss due to photo effects was 52% when DPQ in hexane was exposed to 366 nm light for 1.5 hr. diethylether, minutes
When the solvent was l:l hexane-
a more dramatic loss of 62% was observed after only 5
exposure to the same light.
The loss due to interaction with sulfur was tested by saturating a hexane solution of DPQ with the S 8 form of elemental sulfur, component of the stack emissions ll. gas chromatographed
a known
An aliquot of this solution was
and no DPQ peak was observed.
The unknown reaction
with sulfur leading to the depletion of the DPQ probably occurs in the injeqtion port of the gas chromatograph. DISCUSSION The production of DPQ can affect analytical determinations when its amount is sufficient to mask components For example,
of lesser concentration.
the broad DPQ peak in the capillary column chromatogram
shown in Figure 2 would interfere with the observation and analysis of
No. 6
307
chrysene and 1,2-benzanthracene in stack gases.
in studies of polyaromatic hydrocarbons
The DPQ peak shown here also masks trlphenylphosphate,
a flame retardant observed in stack emissions from a combination coalrefuse fired power plant 12.
The analytical results for these and all
other components which have GC retention times near DPQ are affected. In packed column chromatography the interference problem is greater.
D P Q ~
1< TEMP I
50
200
I
250
Fig. 2. Capillary column (SE-30) chromatogram showing DPQ interference in stack gas extract from Tenax-GC collection. Tenax may still be the most desirable collection medium for many analytical
situations but the user should be conscious of its decompo-
sition to DPQ under certain conditions solvents.
and its solubility
in many organic
308
Uo. 6
ACKNOWLEDGEMENTS The helpful inputs of H. R. Shanks, the instrumental work of M. J. Avery and the laboratory assistance of I. Ogawa are greatly appreciated.
Financial support from DBER of USERDA. LITERATURE
I.
E. Pellizzari,
B. Carpenter,
Technol., 2, 556, 2.
W. Bertsch,
J. Bunch, E. Sawicki, Environ. Sci.
(1975).
R. Chang, A. Zlatkis, ~. Chromatogr.
Sci., I_~2, 175,
(1974). 3.
J. Parsons,
S. Mitzner,
Environ. Sci. Technol., 2, 1053,
4.
W. Bertsch,
A. Zlatkis, H. Liebich,
H. Schneider,
(1975).
J. Chromatogr.,
99, 67 3, (1974). 5.
B. Versino, M. deGroot, F. Geiss, Chromatographia,
6.
J. Mieure, M. Dietrich, ~. Chromatogr.
7.
P. Jones, R. Giammar, l__O0, 806,
8.
Z, 302,
(1974).
Sci.,
l_~l, 559,
(1973).
P. Strup, T. Stanford,
Environ.
Sci. Technol.,
(1976).
"Hazardous Emission Characterization of Utility Boilers",
EPA report
650/2-75-066. .
lO.
H. Finkbeiner, J. Witiak, 38, 3066,
II.
A. Toothaker,
J. 0rg. Chem., 33, A347,
G. Junk, G. Calder,
J. Fritz,
H. Svec,
(1968).
J. Org. Chem.,
(1973).
J. Richard,
R. Vick, G. Junk, submitted to Environ.
Sci. Technol.,
(1977). 12.
G. Junk, R. Vick, M. Avery, unpublished work.
M. Neher and P. Jones ( Anal. Chem., 49, 512 (1977)) published comparable evidence of the decomposition of Tenax-GC to 2,6-diphenyl-p-quinone while this manuscript was in preparation.
Pergamon Press.
Printed in Great Britain.
PROBLEMS WITH TENAX-GC FOR ENVIRONMENTAL SAMPLING R. D. Vick,
J. J. Richard,
Dept. of Chemistry,
H. J. Svec and G. A. Junk Energy and Mineral
Resources Research Institute and Ames Laboratory - U.S.E.R.D.A. lows State University,
Ames,
lows
50011 U.S.A.
(Received in The Netherlands 5 April i~7; accepted for publication I] April 1977) Tenax-GC,
a diphenylphenylene
oxide polymer,
has been used widely
as a collection medium for trace organic pollutants
in atmospheres
because of its desirable accumulation and desorption characteristics. Only minor problems have been reported with nitromethane l, sulfur
compounds 2, a c e t i c
a c i d 3, a c e t o p h e n o n e 4 and b e n z a l d e h y d e 4.
The
possible reported difficulties with extraneous gas chromatograph
(GC)
peaks 5 and undefined background levels 3 can be resolved by proper conditioning and the elimination of inorganic gases such as chlorine. The temperature
stability of Tenax has prompted many investigators
to use thermal desorption for the direct transfer of the collected material to their GC systems I-6. sensitivity,
Although this approach gives high
it does not allow for replicate analyses from a single
sample accumulation.
When replicate analyses are necessary,
a solvent
must be used to elute the material collected on the polymer 3'7'8.
The
solubility of Tenax in many solvents used for elution may cause analytical problems as discussed in this report. A second short-coming of Tenax is related to its instability under certain conditions. piing,
as
has
When used as a sorbent for stack gas sam-
been suggested in several reports 3'5'7'8,
the 2,6-diphenyl
p-phenylene oxide polymer can react to form significant amounts of
3o3
304
~o. 6
2, 6-diphenyl-p-quinone
(2, 6-DPQ). MATERIALS
Apparatus.
A Perkin-Elmer
flame ionization collection, electron
detectors
3920 gas chromatograph
equipped with dual
(FID) and an effluent
splitter for fraction
and a Tracor 550 gas chromatograph
capture detector
Standards. mercially
quinone,
spectrometer
A duPont
(GC-MS) was used for the
analyses.
A primary reference so it was synthesized
the procedure
with a 63Ni
(ECD) were used for the GC analyses.
21-490-1 gas chromatograph-mass mass spectral
equipped
of Finkbeiner
2,5-DPQ
sample of 2,6-DPQ was unavailable from Tenax-GC
and Toothaker 9.
(98%, Aldrich Chemical
by vacuum sublimation
Co.,
and recrystallization,
com-
(Alltech Associates) A commercially Inc.),
by
available
after purification
was used as a secondary
standard. METHODS AND RESULTS Tenax-GC
Solubility.
The solubility
elution solvents was measured These were determined
of Tenax in several commonly used
and the values are listed in Table i.
from gravimetric
differences
after equilibration
of 50 mg of Tenax in 3 ml of each solvent at room temperature
for four
days. The characteristics
of the Tenax remaining
tion may be altered thus limiting solvent containing
its re-use,
after partial
and injection of the
dissolved polymer may be detrimental Table I.
Solubility
Solvent methylene
of Tenax-GC. mg/ml
chloride
dissolu-
16.3
tetrahydrofuran
14.4
benzene
12.2
diethylether
0.3
pentane
0.0
to GC systems.
No. 6
]o5
I d e n t i f i c a t i o n of 2,6-DPQ.
The m a j o r component
of a stack gas extract was f r a c t i o n - c o l l e c t e d a c c o r d i n g to the p r o c e d u r e of Witiak et.al. I0.
in the FID c h r o m a t o g r a m
via the effluent
splitter
The f r a c t i o n - c o l l e c t e d
compound was then sampled by direct insertion to acquire the mass spectral data for i n t e r p r e t a t i o n and eventual 2,6-DPQ.
i d e n t i f i c a t i o n as the
This component was observed w h e n e v e r Tenax was used for
stack gas sampling. Polymer Decomposition.
Parallel
another high temperature polymer,
sampling of stack gas on Tenax and A m b e r l i t e XE-3~O
(Rohm and Haas Co.),
d e m o n s t r a t e d that the quinone was not a component of the stack emission. Samples were collected s i m u l t a n e o u s l y on both polymers by splitting the flow from a single stack probe. graphed with ECD detection.
A peak c o r r e s p o n d i n g to 2,6-DPQ was observed
from the Tenax c o l l e c t i o n only. was shown to be an effective
The separate extracts were chromato-
In a separate test,
Amberlite XE-340
sorption m e d i u m for the analysis of gaseous
2, 5-DPQ. A small amount of the 2,6-DPQ was also p r o d u c e d by the o x i d a t i o n of I0 mg of Tenax using PbO 2 in a c h l o r o b e n z e n e - b e n z o i c A l t h o u g h the reaction conditions stack gas sampling,
acid solution 9.
do not represent those existing during
the results do demonstrate
that Tenax can be oxi-
dized to the quinone in an acid environment. An attempt to produce the quinone by s i m u l a t i n g the stack conditions was unsuccessful.
In this case air was drawn through boiling
HsSO 4 and t r a n s f e r r e d via heated lines to a column of Tenax.
The
extract from this experiment gave no GC peak at the retention time expected for 2,6-DPQ. Losses of DPQ.
Losses due to adsorption,
light and sulfur effects were
m e a s u r e d using solutions of 2,6-DPQ and an internal standard,
n-docosane
(C22). A d s o r p t i o n losses of DPQ were indicated by the n o n - l i n e a r i t y and the inverse r e l a t i o n s h i p of the detector response to contact with metal ss shown in Figure I.
506
No. 6
I
I
I
1.0
B
Fi~. I. FID response of 2,6-diphenyl-p-quinone (DPQ) in hexane relative to C22 internal standard. A. all glass system B. combination glass-metal system C. all metal system
~0.5 hi >
I-.J W n~
q
-C
O.O I 1.0
I 2.0
MICROGRAMS
I
3.0
DPQ
The loss due to photo effects was 52% when DPQ in hexane was exposed to 366 nm light for 1.5 hr. diethylether, minutes
When the solvent was l:l hexane-
a more dramatic loss of 62% was observed after only 5
exposure to the same light.
The loss due to interaction with sulfur was tested by saturating a hexane solution of DPQ with the S 8 form of elemental sulfur, component of the stack emissions ll. gas chromatographed
a known
An aliquot of this solution was
and no DPQ peak was observed.
The unknown reaction
with sulfur leading to the depletion of the DPQ probably occurs in the injeqtion port of the gas chromatograph. DISCUSSION The production of DPQ can affect analytical determinations when its amount is sufficient to mask components For example,
of lesser concentration.
the broad DPQ peak in the capillary column chromatogram
shown in Figure 2 would interfere with the observation and analysis of
No. 6
307
chrysene and 1,2-benzanthracene in stack gases.
in studies of polyaromatic hydrocarbons
The DPQ peak shown here also masks trlphenylphosphate,
a flame retardant observed in stack emissions from a combination coalrefuse fired power plant 12.
The analytical results for these and all
other components which have GC retention times near DPQ are affected. In packed column chromatography the interference problem is greater.
D P Q ~
1< TEMP I
50
200
I
250
Fig. 2. Capillary column (SE-30) chromatogram showing DPQ interference in stack gas extract from Tenax-GC collection. Tenax may still be the most desirable collection medium for many analytical
situations but the user should be conscious of its decompo-
sition to DPQ under certain conditions solvents.
and its solubility
in many organic
308
Uo. 6
ACKNOWLEDGEMENTS The helpful inputs of H. R. Shanks, the instrumental work of M. J. Avery and the laboratory assistance of I. Ogawa are greatly appreciated.
Financial support from DBER of USERDA. LITERATURE
I.
E. Pellizzari,
B. Carpenter,
Technol., 2, 556, 2.
W. Bertsch,
J. Bunch, E. Sawicki, Environ. Sci.
(1975).
R. Chang, A. Zlatkis, ~. Chromatogr.
Sci., I_~2, 175,
(1974). 3.
J. Parsons,
S. Mitzner,
Environ. Sci. Technol., 2, 1053,
4.
W. Bertsch,
A. Zlatkis, H. Liebich,
H. Schneider,
(1975).
J. Chromatogr.,
99, 67 3, (1974). 5.
B. Versino, M. deGroot, F. Geiss, Chromatographia,
6.
J. Mieure, M. Dietrich, ~. Chromatogr.
7.
P. Jones, R. Giammar, l__O0, 806,
8.
Z, 302,
(1974).
Sci.,
l_~l, 559,
(1973).
P. Strup, T. Stanford,
Environ.
Sci. Technol.,
(1976).
"Hazardous Emission Characterization of Utility Boilers",
EPA report
650/2-75-066. .
lO.
H. Finkbeiner, J. Witiak, 38, 3066,
II.
A. Toothaker,
J. 0rg. Chem., 33, A347,
G. Junk, G. Calder,
J. Fritz,
H. Svec,
(1968).
J. Org. Chem.,
(1973).
J. Richard,
R. Vick, G. Junk, submitted to Environ.
Sci. Technol.,
(1977). 12.
G. Junk, R. Vick, M. Avery, unpublished work.
M. Neher and P. Jones ( Anal. Chem., 49, 512 (1977)) published comparable evidence of the decomposition of Tenax-GC to 2,6-diphenyl-p-quinone while this manuscript was in preparation.