Abstract:
Fire debris analysis is a process of identifying Ignitable Liquid Residues (ILR) from
fire debris samples collected at a fire scene. However, analysis of ILR is a complicated
task due to the petrochemical nature of fire debris containing synthetic polymer in the
modern built environment. There, interfering compounds can mask trace levels of ILR
while creating compounds that are similar to target compounds and cause false results
when the analysis is done. One of the commonly found ignitable liquids is petrol and the
main petrol target compounds are aromatics. Polyethylene (PE) interfering compounds
mainly appear as a series of triplets of alkadiene, alkene and alkane. However, the identification
of petrol residues is also somewhat difficult since PE-interfering compounds
can produce more complicity to the chromatogram. This study aimed to recognize the
petrol residues in fire debris in the presence of interfering compounds from PE since
interfering triplets can mask these aromatic target compounds even though they are
not similar to PE interfering compounds. The study comprises the analysis of control
samples of consumer products made of PE that unburnt, pyrolyzed, and burnt as well
as burnt simulated PE samples with various test volumes of petrol. The assessment was
done by passive headspace extraction and GC-MS instrumentation. Aromatic target
compounds in the petrol were unable to detect in petrol-spiked PE samples of 1 μl and
3 μl even Extracted Ion Chromatography (EIC) technique was used for the data analysis
due to masking low abundant peaks. Since PE-interfering compounds are not identical
to petrol target compounds, beyond 5 μl, it was easy to detect all the aromatic target
compounds even though the Total Ion Chromatogram (TIC) was taken into account.
Therefore, PE interference does not affect the identification of considerable amounts of
petrol.
