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Chromatography

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Chromatography is a process used to separate mixtures. The word chromatography is derived from the Greek words ‘khroma’ and ‘graphein’ meaning ‘color’ and ‘to write’ or to represent. Although there are a couple different types of chromatography, in each case a substance is placed onto or into a medium and a solvent is passed through the test substance. In chromatography science, the solvent is called the mobile phase or the carrier fluid and the medium is called the stationary phase. There are four main types of chromatography; these are Liquid Chromatography, Gas Chromatography, Thin-Layer Chromatography and Paper Chromatography. Chromatography is used extensively in forensics, from analyzing body fluids for the presence of illicit drugs, to fiber analysis, blood analysis from a crime scene, and at airports to detect residue from explosives.

Liquid Chromatography is used in the world to test water samples to look for pollution in lakes and rivers. It is also used to analyze metal ions and organic compounds in solutions. Liquid chromatography uses liquids which may incorporate hydrophilic, insoluble molecules. 

Gas Chromatography is used in airports to detect bombs and is used is forensics in many different ways. It is used to analyze fibers on a person’s body and also analyze blood found at a crime scene. In gas chromatography helium is used to move a gaseous mixture through a column of absorbent material. 

Thin-layer Chromatography uses an absorbent material on flat glass or plastic plates. This is a simple and rapid method to check the purity of an organic compound. It is used to detect pesticide or insecticide residues in food. Thin-layer chromatography is also used in forensics to analyze the dye composition of fibers. 

Paper Chromatography is one of the most common types of chromatography. It uses a strip of paper as the stationary phase. Capillary action is used to pull the solvents up through the paper and separate the solutes.

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