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MCounts file7062.ms Ions: RIC all

GC/MS
7.5
TIC is dominated by pyrolysates, a highly weathered sample
Some ignitable liquid components were detected, others unclear
Would be reported as negative!
5.0

2.5

0.0
1 2 3 4 5 6 7 8
minutes
1
353 706 1059 1412 1765 2118 2471 2824
Scans
Figure 5.27 Floor sample from Porsche: TIC from GC/MS analysis.
GC/MS/MS was excellent and would be easily observable by both scientist
and courtroom layperson. The GC/MS/MS analysis resulted in a positive
determination for the presence of gasoline residues, showing that this tech-
nique is perhaps the closest technique to an ignitable liquid detector.
Another case example is for a floor sample taken from a fire-ravaged
Porsche. The TIC in Figure 5.27 shows that few compounds were detected
in GC/MS and a review of mass ion profiles indicated that some ignitable
liquid components were present. Based on this analysis, the sample would
be reported as negative for the presence of an ignitable liquid.
Upon reanalysis with GC/MS/MS, the class daughter ion profiles of m/z
106 (Figure 5.28), m/z 118 (Figure 5.29), m/z 119 (Figure 5.30), and m/z 133
(Figure 5.31) illustrate excellent comparability to the same class profiles in
gasoline. This is another example of a situation where a sample would be
falsely reported as negative by GC/MS, while proven positive for the presence
of an ignitable liquid by GC/MS/MS.

5.2.4.2 Appropriate Sensitivity
Some concern has been reported that analysis by GC/MS/MS may be too
sensitive and may result in the reporting of false positive results for samples
that contain only material incidental to the scene, to the makeup of the
material, or from some environmental background. Similar arguments were
heard when GC/MS analysis was introduced and was suggested to be superior
1
to GC/FID. A study was conducted that showed that this concern was
unfounded. 18 In 1998 this laboratory participated in a test involving the
burning of two automobiles. The opportunity was available to take a large
variety and number of passenger compartment samples from these old,

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