Thin or Thick Layer Chromatography TLC

Thin layer chromatography is in principle similar to paper chromatography when used in the ascending method, i.e. the solvent creeps up the stationary phase by capillarity. The adsorbent (e.g. silica, alumina, cellulose) is spread on a rectangular glass plate (or solid inert plastic sheet). Some adsorbents (e.g. silica) are mixed with a setting material (e.g. CaSC 4) by the manufacturers which causes the film to set on drying. The adsorbent can 

A very efficient thin layer form of circular paper chromatography makes use of a circular glass disc coated with an adsorbent (silica, alumina or cellulose). The apparatus is called a Chromatotron (available from Harrison Research, USA). The disc is rotated by a motor, and the sample followed by the eluting solvent are allowed to drip onto a central position on the plate. As the plate rotates the solvent elutes the mixture, centrifugally, while separating the components in the form of circles radiating from the central point. When elution is complete the revolving circular plate is stopped and the circular bands are scraped off and extracted with a suitable solvent. 

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