TLC is a quick technique for separating and identifying compounds present in a mixture by having them pass through a fixed, inert medium (alumina, silica…) with the aid of a mobile solvent (gas or liquid)  which carries them through the medium.  Each component of the mixture travels through the medium at a different rate as a result of its solubility in the solvent and its affinity for the fixed medium.

TLC  is also commonly used to assess the effectiveness of a purification.