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is also important in the analysis of samples from hot or arid climates as it
has more capability of detecting an ignitable liquid, if present, in very highly
weathered samples.
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As discussed previously, the target class analysis appeared to more
closely resemble the K9 in terms of specificity and sensitivity, and it has been
shown that GC/MS/MS is not overly sensitive for the purposes of this test
for ignitable liquids.
GC/MS/MS can significantly remove pyrolysates and thus make ion chro-
matograms that are representative of a particular class clearer and more
comparable to reference analyses than with GC/MS data. GC/MS/MS results
will easily enable a very clear decision as to whether an ignitable liquid is
present or absent.
GC/MS/MS also improves the specificity and confidence in the result by
providing new chromatographic patterns, with new daughter ion chromato-
grams and more aromatic information, which lessens the dependence on the
alkanes for the identification of petroleum distillates. This is a significant
benefit as alkanes are the class that is most susceptible to significant weath-
ering. Thus, GC/MS/MS improves the analysis for highly weathered samples
by providing additional characteristics for identification.
GC/MS/MS in the target class approach provides an appropriate
improvement in sensitivity while adding robustness to the method. This
sensitivity improvement is more probable at confirming K9 hits than GC/MS
and, up to this point, has not been observed as going beyond the sensitivity
of the K9. GC/MS/MS is the closest method to an ignitable liquid detector
that is both sensitive and specific and provides identity information of the
residue.

5.2.5 Conclusion
In 1999, this laboratory has shown that in its case analyses by GC/MS/MS,
approximately 10% of the samples that were reported as negative by GC/MS
were actually positive after GC/MS/MS analysis. An average of 30% of the
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submitted samples of carpet, wood, soil, and charred debris were found
positive by GC/MS. As a rule, GC/MS/MS is invaluable when a sample
exhibits some ignitable liquid characteristics in a GC/MS analysis. This is
especially true when the interpretation shows that there are insufficient iden-
tification characteristics, which is due to incomplete compound class pat-
terns, heavy sample weathering, weak samples (due to low quantity), and
complex samples due to a large quantity of pyrolysates. The samples that
show some ignitable liquid characteristics were reanalyzed by GC/MS/MS.
Of these samples that would have been reported as negative, 28% were found
to be positive by GC/MS/MS. Reanalysis of samples by GC/MS/MS has very
often provided the additional information to confirm the presence of an

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