Page 243 - Advances in Forensic Applications of Mass Spectrometry - Jehuda Yinon

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kCounts f42 95%wgasoline f6198ms2.ms Ions: 145 all
150 Ion 145 - MS/MS Indans
125 Strong Response - No Pyrolysates
100
75
50
25
0
kCounts f6578ms2.ms Ions: 145 all
50
40 Mixture-Few Pyrolysates
30
20
10
0
kCounts f6579ms2.ms Ions: 145 all
2.5
2.0 Weathered -Many Pyrolysates
1.5
1.0
0.5
0.0
kCounts f6580ms2.ms Ions: 145 all
0.75
Weak Sample & Pyrolysates
0.50
0.25
0.00
1 2 3 4 5 6 7 8
minutes
Figure 5.20 GC/MS/MS mass ion chromatograms are robust to the amount of
pyrolysates present. Top-to-bottom indane ion profiles: 95% weathered gasoline,
gasoline residue in sample of concrete and floor debris, gasoline residue in sample
from car footwell, gasoline residue from under car passenger seat (bottom profile).

GC/MS/MS analysis compared to the reference standard of gasoline, illus-
trating the removal of the pyrolysate response that affects the class ion profile
in the GC/MS trace. Work has also been published with a focus on the
removal of pyrolysates to improve the detection of gasoline. 14
As mentioned previously for indanes, GC/MS/MS also adds robustness
to the method in the presence of a variety of pyrolysates. This is shown in
Figure 5.20. In this diagram of four profiles, the top profile is 95% weathered
gasoline, followed by weak pyrolysates from a sample with a mixture of
concrete and floor debris. The third profile is a very complex sample of
charred debris from the footwell of a car, and the bottom profile is a complex
but weak sample taken from beneath the passenger seat of another vehicle.
As shown, the indane class profile, such as in gasoline, does not vary
significantly with the type or quantity of pyrolysates present, illustrating the
robust nature of MS/MS data. When an ignitable liquid is present,
GC/MS/MS is more capable of determining a positive identification, regard-
less of the amount of weathering or amount of pyrolysates present.
The review of indanes and the use of GC/MS/MS can in some cases
enhance the identification characteristics of incidental material, thus further
reducing the possibility of reporting a false positive result. A recent study 15
has shown that there are specific indane patterns for a variety of inks found

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