Specialised stationary phases

A number of stationary phases/column systems have been developed or optimised for specific applications, particularly for analysis of a complex mixture such as samples from environmental monitoring of atmospheric or water pollution, for example  

FFAP (free fatty acid phase) terephthalic acid modified Carbowax 50/250 340 580 397 602 627 2545 509 

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A number of specialised stationary phases have been developed for the separation of chiral compounds. They are known as chiral stationary phases (CSPs) and consist of chiral molecules, usually bonded to microparticulate silica. The mechanism by which such CSPs discriminate between enantiomers (their chiral recognition, or enantioselectivity) is a matter of some debate, but it is known that a number of competing interactions can be involved. Columns packed with CSPs have recently become available commercially. They are some three to five times more expensive than conventional hplc columns, and some types can be used only with a restricted range of mobile phases. Some examples of CSPs are given below ... 

Over the past decade there have been a number of further significant improvements in the technique. For instance, there are now a wide range of sorbents available in the form of pre-coated plates and the applicability of the technique has also been extended with the increasing range of bonded phase sorbents, e.g. reverse phases (Cg and Cig), those of medium-polarity (amino and cyano) and other specialised layers featuring chiral and mixed stationary phases. 

Bonded phase chromatography (BPC) takes place either under normal phase or reverse phase conditions. In reverse phase mode the stationary phase is non-polar while the eluant is polar, e.g. methanol or acetonitrile with aqueous buffers. Bonded phase packings have superceded the classical packings where the stationary phase was distributed over the surface of the support particles and bound simply by physical forces of attraction. However, due to the problems of solvent stripping and limited hydrolytic stability, these classical systems, though developed for a few specialised applications, have been replaced by organo-bonded stationary phase materials. 

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