Forensic Chemistry
Over the past century, forensic chemistry has become an essential part of almost every criminal investigation. A forensic chemist is a scientist who analyses physical evidence as found on a victim or at the scene of a crime. These scientists work in the field of criminalistics, which deals with analysis, comparison, identification, and interpretation of physical evidence to prove the connections to or existence of a crime. Evidence is examined right down to the molecular level and the compositions of samples are calculated. Criminalists provide information to investigators, attorneys, judges, or juries to help determine the innocence or guilt of a suspect. "Forensic chemical analysis shows a development from the mere quotation of a concentration value to an expert opinion, which helps to explain manifold circumstances of the case under consideration." (Vycudilik, 1999) Forensic chemists may perform one or more of the following tasks: · Analyse drugs and poisons in human tissue and body fluids; including blood alcohol determinations · Examine and compare materials such as fibres, paints, cosmetics, oils, petrol, plastics, metals, soils and gunshot residu
"The extreme sensitivity of gas chromatography makes it ideal for the analysis of trace contaminants in samples or for the detection of tiny amounts of very potent compounds." (Commons, 1991) When samples such as blood are to be analysed for drug content, the sample is first vaporized and then injected into the main body of a mass spectrometer. The gaseous sample is then admitted through a small inlet into an ionisation chamber. Here the sample is bombarded with electrons, forming ions with a single positive charge. The positive ions are accelerated to high speeds by an electric field until they enter a region where there is a perpendicular magnetic field. This field causes the ions to move in curved paths, with a radius dependant on the mass to charge ratio of the ions. Only ions with a particular radius will reach the collector. By changing the accelerating voltage or the strength of the magnetic field, ions of different masses can reach the collector. The collector measures the current due to the different ions and the data is recorded as a mass spectrum. Refer to Diagram 2. It is in these mass spectrums that chemicals such as drugs can be identified. Refer to Figure 1.
Some common words found in the essay are:
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Approximate Word count = 1600
Approximate Pages = 6 (250 words per page double spaced)
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