Separation of Enantiomers by Liquid Chromatography on Chiral Stationary Phases

SEPARATION OF ENANTIOMERS BY LIQUID CHROMATOGRAPHY ON CHIRAL STATIONARY PHASES 

The most widely used CSPs can be classified into three groups (i) CSPs with low-molecular-weight selectors, such as Pirkle-type CSPs, ionic- and ligand-exchange CSPs, (ii) CSPs with macrocyclic selectors such as CDs, crown-ethers and macrocyclic antibiotics, and (iii) CSPs with macromolecular selectors such as polysaccharides, synthetic polymers, molecular imprinted polymers and proteins. It can be observed that several of the chiral selectors applied in CE are used in LC. They are then bonded or coated to an inert carrier to form the CSP. 

Pirkle Type r-Donor, r-Acceptor Chiral Selectors 

Pirkle-type CSPs do not involve ionic interactions and therefore are almost exclusively operated in the normal-phase mode. The use of subcritical carbon dioxide based mobile phase, i.e., subcritical fluid 

The r-donor phases (typically naphthyl-amino-acid derivatives covalently bonded to silica) require the analyte to contain a r-acceptor group such as the dinitrobenzoyl group. The dinitrobenzoyl group can easily be added to a wide range of compounds such as alcohols, amines and carboxylic acids using dinitrobenzoyl chloride, isocyanate or dinitroanaline, as already mentioned above. 

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