Chemistry Reference
In-Depth Information
8
Forensic Applications of
Gas Chromatography
8.1 Introduction
In this chapter the applications of GC in five different contexts will be con-
sidered, namely, drug analysis, forensic toxicology, fire debris, paint analy-
sis and food and fragrance analysis. Each will be considered in turn using
examples to illustrate its use of GC in a forensic application.
8.2
Drug Analysis
8.2.1 Introduction to Drug Analysis
Drugs of abuse such as amphetamines, heroin and cocaine are drugs that
are sold by drug dealers and are commonly referred to as street drugs. Street
drugs are rarely, if ever, pure substances. They are usually 'cut' with other
substances, such as paracetamol, or other less pharmacologically active
drugs, such as aspirin. They may also contain other compounds such as talc
and/or sugars. This means that if a suspected drug sample requires analysis,
there may be more than one compound present. However, as drug analysts,
we are trying to establish if any drugs are present (or not) and, if necessary,
to establish how much is present. It may also be necessary to identify those
substances used to 'cut' the items or to carry out impurity profiling.
8.2.2 Forensic Analysis of Drugs
The amount of the substance suspected of being a controlled drug will deter-
mine what tests can be carried out. For example, a swab from a set of scales
thought to be used for the weighing of cocaine is classed as a trace sample.
This means that the sample size is limited; as a consequence, the presump-
tive colour tests and thin layer chromatography (TLC) approaches cannot be
carried out here. In this situation, GC-MS would typically be used. If, on the
other hand, a 1 kg block of off-white powder has been submitted for analysis,
we have a bulk sample, which means that we can carry out more tests than
we can with the trace sample.
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