area of toxicology involves testing for the use of illegal
substances, poisons and alcohol. Using samples from
a suspect such as hair, a toxicologist can confirm whether
a person has used illegal drugs weeks ago or only yesterday.
Urine and blood tests can reveal alcohol levels and
whether someone was poisoned.
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in the body
for drugs follows a certain procedure. First, a simple
test is done to determine whether a chemical is present.
If it is found that there is a chemical present, more
complex testing is conducted to measure the quantity
and type of illegal substance. The preliminary test
involves an immunoassay
kit which changes colour when drugs in a sample of urine
combine with the antibodies
that are present in the kit test.
such as this drug carousel play an important role in
the toxicology units. Photo courtesy of Lothian
and Borders Police Forensics Lab.
drugs and alcohol are tested using chromatography,
which involves separating chemicals based on the
speed at which they move in liquid and gas. The
essential testing device in the toxicology department
is gas chromatography. Consisting of a narrow
tube containing loosely packed solid particles,
a non-reactive gas, for example, nitrogen,
flows through the tube. When the sample to be
tested is inserted, every individual chemical
passes through the tube at varying speeds. Timing
when each chemical arrives at the exit point identifies
the composition of any substance mixture. These
results are then placed on a computer database,
where each substance appears as a peak on a graph.
The peaks that are identical to a known
an indian hemp plant often trafficked illegally.
Photo courtesy of www.free-stock-photos.com.
make a positive result. Liquid chromatography
involves the same process, substituting gas for
In The Body
as mentioned earlier, is used in identifying poisons,
whether it was accidental, suicidal or homicidal. The
testing is this time done on the victim using samples
taken during the autopsy. The liver, as this is the
part of the body that filters out the body's toxins,
and blood samples are the most useful in testing for
poisons, but other samples such as bile,
which holds antidepressants, heroin and morphine are
also used. Flammable substances such as solvents are
present in the lungs as a result of poisoning and the
victim's hair stores, a record of poisoning, as lines
along the strand of hair in
chronological order. These samples are analysed
using immunoassay and chromatography methods, the same
as testing for substances in living individuals.
Strychnine, a colourless crystalline poison, is an exmaple
of a toxin which can potentially kill. Photo courtesy
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