Thin Layer Chromatography

ABSTRACT
The public profile of forensic science has dramatically increased in recent decades and there has been a corresponding rise in the number of students undertaking forensic science degree courses at tertiary level with the view to a professional career in this field. During this period the application of modern analytical techniques to the examination of small and portable cost-effective instrumentation. The availability of new techniques has led to a greater choice of tools that can be employed to analyse forensic specimens. An understanding of a broad range of analytical tools is required by today’s forensic chemist and is an important aspect of their training.
The aim of this project work is to provide an overview of the most commonly

The liquid will slowly raise up the plate by capillary action causing the sample to become distributed between the stationary phase and the moving liquid phase. Because most compounds are colourless, the materials must be visualized by placing the plates under ultraviolet light or spraying the plate with a chemical reagent. The distance a spot travels up a thin-layer plate can be assigned a numerical value known as the Rf value.
Theory: The technique of thin-layer chromatography (TLC) uses a solid stationary phase and a moving liquid phase to separate the constituent of a mixture. A thin-layer plate is prepared by coating a glass plate with a thin film of a granular material, usually silica gel or aluminium oxide. This granular material serves as the solid stationary phase and is usually held in place on the plate with a binding agent such as plaster of Paris. If the sample to be analysed is a solid, it must first be dissolved in a suitable solvent and a few microliters of the solution spotted with a capillary tube onto the granular surface near the lower edge of the plate. A liquid sample may be applied directly to the plate in the same manner. The plate is then placed upright into a closed chamber that contains a selected liquid, with care that the liquid does not touch the sample

Chromatography means of separating and tentatively identifying the components of a mixture. Gas chromatography separates mixtures on the basis of their distribution between a stationary liquid phase and a mobile has phase. In GC, the moving phase is actually a gas called carrier gas, which flows through a column. The stationary phase is a thin film of liquid contained within the column. After a mixture has traversed the length of the column, it emerges separated into its components. The written record of this separation is called a chromatogram. A direct connection between the GC column and mass spectrometer allows each component by high-energy electrons produces a fingerprint pattern of the substances being