Page 244 - Advances in Forensic Applications of Mass Spectrometry - Jehuda Yinon

1522_book.fm Page 217 Thursday, November 13, 2003 9:58 AM

kCounts 1106897 ms RIC all
Cash Register Receipt - Blue - GC/MS
400
300
200
100
0
MCounts 1106897 ms Ions: 57 all
70
Cash Register Receipt - Blue - GC/MS
60 Alkanes (Ion 57)
50
40
30
20
10
0
Counts 19616 ms 2 ms Ions: 131 all
400
Cash Register Receipt - Blue - GC/MS/MS
300
200
100
0
kCounts 18616 ms 2 ms Ions: 145 all
3.0
Cash Register Receipt - Blue - GC/MS/MS
2.5
2.0
1.5
1.0
0.5
0.0
1 2 3 4 5 6 7 8
minutes
Figure 5.21 GC/MS/MS can display unique profiles of some incidental
materials.

in newspapers, courier slips, magazines, etc. that are enhanced in GC/MS/MS,
providing a well-recognized marker that the forensic scientist can use in
interpretation of the potential presence of ignitable liquid characteristics. An
example of indanes in a cash register receipt is shown as the profiles of ions
at m/z 131 and 145 in Figure 5.21.
This lab has defined criteria for situations where reanalysis by GC/MS/MS
for confirmation is considered. These criteria are based on the minimum
presence of branched alkanes and dimethylbenzenes in an initial GC/MS
analysis. The detection of the straight chain (n-alkanes) and branched alkanes
requires particular attention. The detection of alkanes is important. They
are, however, already so fragmented that there is no molecular ion or other
significant diagnostic ions to isolate as a precursor ion for CID fragmentation
in the second stage MS. MS/MS is very sensitive for aromatic components,
but to obtain the branched and straight-chain alkane pattern at all, this class

© 2004 by CRC Press LLC