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168 Mass Spectrometry in Forensic Science

TABLE I Common Accelerants
Main type
(approximative boiling point) Major components Examples of commercial products Abundant mass fragments
Light petroleum distillates n-Alkanes, branched alkanes Petroleum ethers, pocket lighter, rubber 42, 43, 56, 57, 71, 85
◦
(<120 C) cement solvents, lacquer thinners
◦
Gasolines (50–220 C) Alkylbenzenes, naphthalenes Automotive gasoline, lantern fuels 91, 92, 105, 106, 115, 116,
118, 119, 120, 134, 141,
142, 148, 156
Medium petroleum distillates n-Alkanes, branched alkanes, Charcoal starters, paint thinners, mineral 43, 55, 57, 71, 82, 83, 91, 105,
◦
(60–200 C) alkylbenzenes spirits, torch fuels, dry-cleaning solvents 120, 134, 138
◦
Kerosene (90–290 C) n-Alkanes, branched alkanes, Fuel oil, aviation fuel, insect sprays, 57, 71, 91, 106, 120, 128, 134,
alkylbenzenes, naphthalenes charcoal starters 142, 148
Heavy petroleum distillates n-Alkanes, branched alkanes, Fuel oil, diesel fuel 43, 57, 71, 128, 142
(120–410 C) naphthalenes
◦
Varia Alcohols, ethers, α-pinene Solvents, turpentine 31, 32, 45, 59, 73, 74, 93

whether the incident was of incendiary origin or not. The ceased were also searched for fuel components. On the
U.S. National Fire Protection Association reported that chromatogram monitoring the sum of all ions (TOT), no
over 100,000 fires in 1994 were arson related and more peaks appeared, but after it had been reconstructed with
than 500 persons lost their lives in these fires. In terms the selected ions at m/z 78 + 91 + 92 a number of aro-
of loss of human life, houses, properties, and goods, this matic hydrocarbons showed up. These could, however,
type of incidence, extracts a large toll from society as stem either from a fuel or from pyrolyzed plastics. The
well as from individuals, and makes the forensic task presence of MTBE at m/z 73 indicated, however, that
urgent. gasoline had been used to set the fire. This piece of evi-
The list of the most common accelerants, shown in dence pointing to arson could not have been brought light
Table I, may at first give the impression that these would without MS.
rapidly gasify along with the burning solid materials and
thus not become detectable, but it is not always so. Traces
C. Environmental Issue
of the fuel often remain in some closed areas of the fire
scene even after the temperature has reached perhaps Growing global use and transportation of chemicals with
◦
1000 C, and these accelerant residues may be detectable potential deleterious effects on the environment have
after proper sample collection. prompted forensic scientists to develop methods for
By virtue of its high sensitivity and specificity, GC/MS
is well suited for searching trace amounts of test materi-
als for residues of accelerant components. As reported in
the literature on material spiked with accelerants, specific
GC/MS patterns of different types of fuels may be used
to identify an accelerant. A problem with this approach
is that burning plastics and other solid materials release
hydrocarbons that are the same as those in accelerants and
thus may contribute to a false positive result by tainting
the test material. The use of fuel labels may overcome
this hurdle. Methyl-tertbutyl-ether (MTBE), which is an
additive in gasoline, has been suggested as such a marker.
Owing to its low boiling point (55.2 C), however, it disap-
◦
pears rapidly during a fire and is therefore only detectable
in postmortem materials from a fire victim who has in- FIGURE 10 Arson analysis of blood sample. The mass chro-
haled MTBE. Figure 10 shows such an example from the matogram at A shows the total ion current (the sum of all fragments
recorded). The reconstructed mass chromatogram at B shows the
real-life fire of a villa, which was completely destroyed.
ions with the sum at m/z 78, 91, and 92 to monitor aromatic hydro-
No accelerant residues were spotted in the ashes around carbons, and the reconstructed mass chromatogram at C shows
the body of a fire victim, so blood samples of the de- the ions at m/z 73 to monitor MTBE.