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| Toxicology |
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| The
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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Choose one of the topics below to read more:
--> Preliminary
testing
--> Chromatography
--> Toxins
in the body
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| Preliminary
Testing |
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| Testing 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. |
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| *Machinery
such as this drug carousel play an important role in the toxicology
units. Photo courtesy of Lothian
and Borders Police Forensics Lab. |
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| Chromatography |
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Both
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 drug make a
positive result. Liquid chromatography involves the same process,
substituting gas for liquid. |
| *Marijuana,
an indian hemp plant often trafficked illegally. Photo courtesy
of www.free-stock-photos.com. |
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| Toxins
In The Body |
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| Chromatography,
as mentioned earilier, 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. |
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| *
Strychnine, a colourless crystalline poison, is an exmaple of a toxin
which can potentially kill. Photo courtesy of Steve's
Vegetable Empire. |
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