Chiral ion exchangers

Quinine and quinidine carbamate phases have recently been commercialized by Daicel [23]. These selectors derived from natural alkaloids of the chinolin-type show great potential for enantiomer separations of polar analytes, such as N-derivatized amino acids and peptides, amido sulfonic adds, and non-derivatized acids. 

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Sellergren, B. and Shea, K. J., Chiral ion-exchange chromatography Correlation between solute retention and a theoretical ion-exchange model using imprinted polymers, /. Chromatogr. A, 654, 17, 1993. 

Separation by HPLC typically falls into one of six categories chiral, ion exchange, ion pair, normal phase, reversed phase, or size exclusion. Reversed phase is the most common type employed, and although various detection principles can be used in HPLC, UV is the most typical. 

TABLE 3 Chiral Compounds Tested for Separation by Chiral Ion-Exchange Chromatography... 

CSPs based on SOs with charged functional groups can be classified and operated as chiral ion exchangers if oppositely charged functional groups are present in the SA to be resolved. Inherently connected to this mode of separation is the use of buffered and pH-controlled mobile phases, to adjust and to control the adsorption-desorption processes. Accordingly, the primary mode of operation is in the reversed-phase mode or, alternatively, with polar-organic mobile phases. 

The above chiral ion-exchange concepts are based on macromolecular and intermediate size SOs with scarcely defined stereodiscriminating binding sites. 

In a different concept chiral ion-exchange type CSPs based on low molecular weight selectors have been developed. These systems have certain advantages, as listed below. 

At present CSPs based on polysaccharide derivatives, chiral ion exchangers, and macrocycUc antibiotics are most commonly used for CEC enantioseparations, but CyD-based CSPs played an important role in establishing of this technique in both open tubular [64, 65] and packed capillary format [65]. 

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