The Use of Cyclodextrins as Chiral Selectors

Cyclodextrins are the most popular of the many chiral selectors used in CE because they have many of the desirable features of the ideal chiral selector. Cyclodextrins are used in about two thirds of the literature applications of CE for the separation of enantiomers [1]. Cyclodextrins show good enantioselectivity for a wide range of analytes, are transparent to UV light down to low wavelengths, and have good water solubility. Cyclodextrins are available in a range of sizes and chemistries, usually give fast kinetics for the formation and breakdown of complexes with enantiomers, and are relatively cheap. Cyclodextrins were amongst the first chiral selectors employed in CE and their successful application has followed their use as chiral stationary phases in GC, TLC, and HPLC, and as mobile phase additives in TLC and HPLC. Most early workers used the parent α, β, and γ-cyclodextrins but most interest has now shifted to the substituted cyclodextrin derivatives, particularly those of β-cyclodextrin. Charged cyclodextrins are rapidly growing in popularity with anionic derivatives such as various sulphonated β-cyclodextrin being the most widely used.