Applications:

The applications of ion pair chromatography frequently overlap with those of ion- exchange chromatography. Ion chromatography is generally used for the separations which are difficult to attain with ion exchange chromatography. A typical example is the separation of chlorate and nitrate which is difficult to achieve on an ion exchange but easily attained by ion pair chromatography.

Size exclusion chromatography is a very useful form of liquid chromatography employed for the separation of high molecular weight substances. This is also called gel permeation or gel filtration chromatography. Two important types of column packing material used for chromatography in aqueous phase are cross-linked dextrans and polyacrylamide. The procedure responsible for the separation is due to the distribution of solute between the aqueous phase within the gel particles and external water. The selectivity is achieved on the basis of pore size of the gel. A solute which is small enough may enter the gel phase. Within a column, that will have retarding effect. The molecules which have penetrated the gel, that will spend their time sheltered from the moving phase. On the other extreme if the molecule is huge sufficient not to be able to enter the pores will spend all the time in the mobile phase and move rapidly through the column. In between there will be molecules of intermediate size which can penetrate in some degree and their movement down the column will be somewhat retarded. This forms the basis for separating the molecules of different sizes.