Partition Chromatography:
As already pointed out it is being used in two forms of bonded-phase (BPC) and reversed phase chromatography (RPC). Both of these forms are suitable for most HPLC separations ranging from mixtures of weakly polar to highly polar and ionic compounds. Reverse phase chromatography using octadecyl (C18) columns and methanol/aqueous buffers or acetonitrile/water mobile phases is by far the most widely used. Ion pair chromatography offers the advantages of greater efficiency and column stability and more selectivity in the separation of ionic compounds compared to bonded phase or conventional ion exchangers.
The reverse phase technique comprises nearly half of all the LC methods described in literature. It provides optimum retention and selectivity when compounds have no hydrogen bonding groups or have a predominant aliphatic or aromatic character as typically illustrated in separation of solutes based on the size and structure of alkyl groups in a series of phthalate esters.