Two-dimensional chromatography:

Once upon a time, term planar chromatography included two-dimensional chromatography though it has now come to signify the coupling of two chromatographic techniques with different mechanisms of separation. It is called 'planar' because the stationary support consists of the plane surface of a paper or smooth glass plate. It involves paper chromatography (PC) and thin layer chromatography (TLC) that are the simplest of all other forms of chromatographic techniques. It also includes electrophoresis or electro chromatography where the movement of mobile phase is assisted by electrical potential. Therefore, it will not be discussed here.

The paper chromatography (PC) and thin layer chromatography (TLC) have the advantage of being simple, fast and inexpensive. Those have been hugely used for the qualitative identification of different constituents in a mixture though these could be also used for quantitative determination of the components. However, PC is not used so commonly these days and as of now, planar chromatography based on TLC has found widest applications in organic synthesis laboratory, drug industry, and clinical research and for investigating biochemical processes.  In both the cases, sample is spotted with a micropipette on to a paper or a plate and then the chromatogram is developed using a suitable organic solvent. Every constituent present in the sample is identified on the basis of colour development using a suitable detection system.