Examination of Firearms Review: 2007 to 2010 - Interpol

considering examining the total ion chromatograms (TICs), extracted ion profiles
(EIPs) and ASTM methods have generated discussion. The so-called average
gasoline pattern which can be applied to case work was a point of interest. The
examiner, on the other hand, might notice an exceptional pattern that can produce
difficulties in identification the substance as gasoline originated. A variety of refineries
contributes to the diversity of chemical compositions in gasolines. The article
concludes that two ASTM methods (1387 and E1618) can provide general guidelines
for forensic work. 56
In relation to the above-mentioned subject, discrimination of diesel oil by origin and
type is also discussed. Methods are physicochemical instead of gas chromatographic,
and results are valuated by mathematical methods, such as principal component
analysis and linear discriminant analysis. 57 According to the study, determining the
origin and type of a diesel sample is possible without the use of complimentary
assays. On the other hand, grouping by composition is not distinguished. 57
Furthermore, spectrofluorimetric methods are used in order to determine the residual
oil in diesel oils. There the mixture of fuels is under research due to the obligatory
commercialization of biodiesels. The synchronous fluorescence spectra are able to
categorize diesel oil samples and make groupings by using linear discriminant
analysis. 58 In the same series of studies, gasoline adulteration is identified by using
comprehensive two-dimensional gas chromatography. A generic method is
developed in order to assess the adulteration of gasolines; this method of analysis
can be a powerful tool in solving similar analytical problems with complex mixtures. 59
Since the use of base stock in motor oils has many applications, the possible
association of a motor vehicle in arson is probable. It is in these cases that
comparing the oils becomes relevant. Some investigations have been made into
comparisons of fuel oils and motor oils. Distinguishing several different oil brands and
grades from each other is possible by using high temperature gas chromatography
mass spectrometry (HTGC-MS) with a programmable temperature vaporizer injector.
Increasing viscosity lengthened retention times and while “the chromatogram
envelopes” broadened identification of the samples whereas unused oils from the
same brand and viscosity could not be distinguished. 60 In another example,
composition and a weathering pattern of heavy fuels is analysed based on IR, GC-
FID and GC-MS analyses 54 , and further with high temperature two dimensional gas
chromatography HT-GC x GC 61 and easy ambient sonic-spray ionisation mass
spectrometry. 62
In a Japanese study, detection of total sulphur in fuels demonstrated that different
fuel types could be distinguished by using gas chromatography with atomic emission
detection (GC-AED). Due to the high degree of selectivity and sensitivity in GC-AED
and detection of characteristic elements in compounds, detection of trace amounts of
substances in fire debris samples is possible. Furthermore, although the distillation
characteristics had altered, discrimination of fuel types was successful. 48
A novel concept of isomer abundance analysis (IAA), supersonic gas
chromatography mass spectrometry, has been used in order to widen the range of
fuel and hydrocarbon analysis. The method reveals molecular ions in all
hydrocarbons and this helps to obtain their isomer distribution and provide
identification for them. Due to the trace amounts of fuels collected from fire scenes,
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