Fundamental Organic Chemistry

2- Thin-Layer Chromatography(TLC)
Thin-layer chromatography is a variation of column chromatography.
Instead of a column, a strip of glass or plastic is coated on one side with a thin
layer of alumina or silica gel.
In a TLC analysis, about 10 µL of a solution of the substance to be tested is
placed (“spotted”) in a single spot near one end of the plate, using a micro
capillary. The plate is “developed” by placing it in a jar with a small amount of
solvent. Shows a TLC plate in a developing jar. The solvent rises up the plate by
capillary action, carrying the components of the sample with it. Different
compounds in the sample are carried different distances up the plate because of
variations in their adsorption on the adsorbent coating. If several components are
present in a sample, a column of spots is seen on the developed plate, with the
more polar compounds toward the bottom of the plate and the less polar
compounds toward the top.
As an analytical tool, TLC has a number of advantages: it is simple, quick,
inexpensive, and requires only small amounts of sample. Tlc is generally used as
a qualitative analytical technique, such as checking the purity of a compound or
determining the number of components in a mixture. We can use TLC to follow
the course of a reaction by checking the disappearance of starting material.
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