Biological Evidence Analysis Essay

Purification and analysis of biological evidence in forensic science are the key methods in order for scientists to be able to identify victims, convict the right criminals and administer justice. Nowadays, technology has developed a variety of techniques that help forensic scientists to complete their research easier and faster. In this coursework, will be discussed the current methods that scientist use for purification purposes and their important role in forensic evidence analysis.
According to IUPAC definition, ‘’chromatography is a physical method of separation, in which the components to be separated are distributed between two phases, one of which is stationery whilst the other moves in a definite direction’’. [Kirkham19]
Chromatography

In High Performance Liquid Chromatography the solvent is forced through under high pressures of up to 400 atmospheres. The compounds travel in different speeds through the column. Retention Times( tR) is the time a compound needs to travel through the column to detector. Each analyte has a different retention time for several reason such as the pressure used, the nature of stationery phase, the temperature of the column and the exact composition of the solvent. There are two variants in HPLC based on the relative polarity of the solvent the normal and the stationery phase. In Normal phase, the column is filled with small silica particles and the solvent is non polar. The compound will run through the column where the non polar mixture will not stick to the silica and will pass the column faster than the polar compounds which will stick to the column. In reversed phase the column is the same size as the normal phase. The only difference from normal phase is that the column now is modified in order to attach long hydrocarbon to it surface. When a polar solvent is used strong attractions between the polar solvent and polar molecules in mixture being passed through the silica. Polar molecules will spent most of the time moving with the solvent because there will not be as much as attraction between the hydrocarbon chains attached to silica and the polar molecules in the solution. About the non polar mixtures, because of the Van der Waals forces will tend to form attractions with hydrocarbon