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Cllromalographoc
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VOl 24. F80ruilry 1986
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respective of whether theyare hydrocarbon or heteroatomcom–
pounds. This is the result of the additional ionization process
thai occurs at the surface of the catalytic CFID source.
Asanticipated. theTlD·I·N, mode in Figure 8 provideshigh
specificity and sensuiviry to certain nitre- and polychlorinated–
phenols. The responses 10 pentachlorophenol and a-nurcphenol
aremore than
100
times larger than
the
CFID responses to these
compounds. Comparing the responses of a-nirrophenol and
z-nurcehenct
again illustrates a significantlygreater TID· I·N,
response for the isomer with the nitro group located at the
4_
position in the molecule.
In the third chromatogram in Figure 8, the low work func–
tion thermionic source (TID·I) was operated in a detector gas
environment comprisedofapproximately equal flowsofN, and
air. This illustrates that the composition of the gas environment
is an additional parameter which can
be
used to suppress the
response to certain compounds while enhancing the response
10 others.
The bottomchromatogram in Figure 8 shows the analysisof
the phenol sample for the
case
where beth detector gases I and
2
are air. Responses are nowobtained for all the chlorinated
and nitro-phenols, with the dinitro-compounds
continuing
to
give the dominant responses. The responses to 2-nitrophenol
and 4-nitrophenoJ are now comparable, in contrast to the
TID-I-N, response in which therewas significanl preference for
the nitro group in the
e-lccancn vs.
the 2-location.
Figure 9 demonstrates the high specificity for lead alkyls in
TIO-I
- N
2/
A I
R
3OlIO- 8A
T IO- l -AI R
GASOLINE
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Figure 8.Chromat09rant$ showingdillerent
IT1lXles
otdetector responsetopnenol
samplecont3lnlng 2-chlorophenol; 2-nitrophenol: phenol;2.4·dlmelnyipnenol;
Z.4·diclllolopl'lenol:2.4.6-triCnlorop/'lenol: 4-<:hloro·m·creso!:2.4-dinllfophenol:
4,6-dlnllro-o-cresol; pentactacrccoenof: and4·nitrophenol lnorder of increas–
ing retenren rsne. Column: SP·1240. 100° to210"Cat 8°/mln.
47
