Thin layer chromatography (TLC) is an important technique for identification and separation of mixtures of organic compounds. It is useful in:

Identification of components of a mixture (using appropriate standards)
following the course of a reaction, analyzing fractions collected during purification, analyzing the purity of a compound.

In TLC, components of the mixture are partitioned between an adsorbent (the stationary phase, usually silica gel, SiO2) and a solvent ( the mobile phase) which flows through the adsorbent.

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