Forensic Applications of Gas Chromatography - Forensic Applications of Gas Chromatography - page 119

Table 8.4 GC-MS Instrument Parameters for the Analysis of Fire Debris and
Accelerant Standards
GC Method Parameters Mass Spectrometry Parameters

Temperature program: 50°C held for 1 min; increase to
225°C at 10°C/min and hold for 1.5 min
Split: 20:1
Total run time: 20 min
Injection port temperature: 250°C
Carrier gas: Heat a flow rate of 1.0 mL/min
MS transfer line temperature: 280°C

Ion source temperature: 250°C
Mode: positive ion
Full scan range: 50-250 Da

can be seen in the following examples.) From the sample of fire debris, the
chromatogram shown in Figure 8.30 was found.
Using the software available on the GC-MS system, it is possible to
extract certain ions from the chromatogram (see also Section 8.3.6). If, for
example, we are looking for the aromatic component in the chromatogram,
it would be appropriate to extract the ions 91, 105 and 119 Da. These ions
were extracted from the fire debris collected from the scene and are shown
in Figure 8.31.
Other classes of compounds also have associated ions that will be
extracted (examples are shown in Table 8.5). However, for the purposes of
this example, we shall use only the aromatic components. Initially, the chro-
matogram from the fire debris compared to the standard liquids will be con-
sidered (Figure 8.32).

550000

500000

450000

400000

350000

300000

250000

200000

150000

100000

50000

0

Time --> 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.0011.00 12.0013.00 14.00 15.0016.00

Time (minutes)

Figure 8.30 Total ion chromatogram from SPME-GC-MS analysis of fire debris.