Classification:

If we look into the definition of chromatography and the situation spelt out above, chromatography can be classified on the basis of the following:

• The shape of the solid support.
• The nature of the mobile phase.
• An mechanism responsible for separation.

If we go by the shape of support in chromatography, there will be three dimensional (column) and two dimensional (thin layer and paper) chromatography. In 2D chromatography, there will only be two types of chromatography, thin layer and paper and all the other forms of chromatography will fall under the head of column chromatography. This is very easy a classification and does not take into consideration the nature of the mobile phase and the process responsible for separation. Moreover, 2D chromatography is operated using the liquid only as a mobile phase.

If the classification is done purely on the basis of the nature of mobile phase, there will be three types of chromatographic techniques - liquid, gas and supercritical fluid chromatography. Here, a first two are well known and various advancements have already been made in these two forms of chromatography. Supercritical fluid chromatography is relatively new and does not figure so frequently. Inspite of some advantages it has still to become popular. Again, in this category of classification, a large number of chromatographic techniques with varied modes of separations fall under the head of liquid chromatography.