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Encyclopedia of Physical Science and Technology EN016H-959 August 1, 2001 11:6

Toxicology in Forensic Science 907

TABLE II Drugs Commonly Targeted in Forensic Toxicology Investigations
Most common drugs Alcohol
Amphetamines, benzodiazepines, cannabis, cocaine and opiates
Common ethical drugs Antidepressants including tricyclics, serotonin reuptake inhibitors, and monoamine oxidase inhibitors
Antipsychotics drugs such as phenothiazines, haloperidol, olanzapine, or clozapine
Other analgesics and anti-inflammatory agents
Digoxin, anti-arrhythmic drugs, anti-hypertensive drugs, and many other cardiovascular drugs
Less common drugs GHB, LSD, and other hallucinogens
Anabolic steroids and other performance-enhancing drugs
Barbiturates and older sedatives and hypnotics such as methaqualone
Volatile substances such as butane, or gasoline
Various domestic, industrial, and agricultural poisons such as organophosphates, or solvents

IV. WHAT CHEMICALS SHOULD niques such as high-performance liquid chromatography
BE TARGETED? (HPLC), gas chromatography (GC), and capillary elec-
trophoresis (CE). Mass spectrometry (MS) is the defini-
It is common to find a variety of ethical and illicit drugs tive technique used to establish proof of structure of an
or unusual poisons. Worldwide experience also shows that unknown substance and can be linked to GC, HPLC, and
forensic cases often involve more than one drug substance. more recently to CE.
High rates of multiple drug use are found in deaths from The use of appropriate extraction techniques is criti-
misuse of drugs and also in perpetrators of violent crimes. cal to all analytical methods. Three main types of extrac-
It is also well known by forensic toxicologists that the tions are used: liquid–liquid, solid-phase, and direct injec-
information provided to the laboratory concerning pos- tion. Traditionally, liquid techniques have been favored in
sibledrugusemaynotagreewithwhatisactuallydetected. which a blood or urine specimen is treated with a buffer of
It is therefore strongly recommended that laboratories pro- an appropriate pH followed by a solvent capable of parti-
vide a systematic approach to their analyses and include tioning the drug out of the matrix. Solvents used include
as wide a range of common ethical and illicit drugs as fea- chloroform, diethyl ether, ethyl acetate, toluene, hexane,
sible. A laboratory using this approach would normally various alcohols, and butyl chloride and mixtures thereof.
include a range of screening methods often incorporat- The solvent is then isolated from the mixture and either
ing both chromatographic and immunological techniques. cleaned up by another extraction process or evaporated to
Drug classes such as alcohol, analgesics, opioid and non- dryness.
opioid narcotics, amphetamines, antidepressants, benzo- Solid-phase techniques are becoming increasingly fa-
diazepines, barbiturates, cannabis, cocaine, major tran- vored, as they offer the ability to extract substances of
quilizers (antipsychotic drugs), and other CNS-depressant widely differing polarity more readily than with liquid
drugs should be included (Table II). techniques.
The incorporation of a reasonably complete range of Direct-injection techniques into either GC or HPLC
drugs in any testing protocol is important, as many of instruments bypass the extraction step and can offer a
these drugs are mood altering and can therefore affect be- very rapid analytical process. In GC, solid-phase micro-
havior as well as the health of an individual. Persons using extraction (SPE) can be used, while HPLC tends to require
benzodiazepines, for example, will be further affected by use of pre-columns that are backflushed with the use of
alcohol and other CNS-active drugs. The toxic concen- column-switching valves.
trations of drugs are also influenced by the presence of
other potentially toxic drugs. For example, the toxicity of
heroin is affected by the concomitant use of alcohol and VI. INITIAL TESTS AND CONFIRMATION
other CNS-depressant drugs.
The process of conducting toxicology in forensic science
is similar to other analytical disciplines, in that sufficiently
V. TECHNIQUES USED suitable analytical techniques need to be employed that
are appropriately validated. The foremost goal is the need
The range of techniques available to detect drugs in to provide a substantial proof of the presence of a sub-
specimens or physical exhibits varies from commer- stance(s). The use of conventional GC, TLC, or HPLC by
cial kit-based immunoassays and traditional thin-layer themselves would not normally be sufficient to accept un-
chromatography (TLC) to instrumental separation tech- equivocal proof of the presence of a chemical substance.