Advances in the Use of Cyclodextrins as Chiral Selectors in Capillary Electrokinetic Chromatography: Fundamentals and Applications

Capillary electrokinetic chromatography is generally recognized as a versatile and robust capillary electromigration technique for the separation of enantiomers. In this mode, one or more chiral selectors are added to the background electrolyte acting as pseudostationary phases. Within the various chiral selectors that have been applied to enantioseparations in capillary electrokinetic chromatography, cyclodextrins are by far the most often used selectors because of their versatility, structural variety and commercial availability. This is reflected in the large number of applications of cyclodextrins to analytical enantioseparations that have been reported between January 2012 and July 2016, the period of time covered by this review. Many of these applications cover aspects of life sciences such as drug analysis, bioanalysis or food analysis. Despite the large number of commercially available cyclodextrins, new derivatives have been developed in order to achieve altered enantioselectivities or to further broaden the application range. Cyclodextrins have also been used to demonstrate the validity of theoretical models of electromigration as well as complex formation equilibria in enantioseparations. Finally, recent studies for an understanding of the molecular basis of the chiral recognition between cyclodextrins and the analytes are discussed.