Role of the Cyclodextins in Chiral Separations

Zoltan Juvancz, Environmental Engineering, Obuda University, Budapest, Hungary

Cyclodextrins have been extensively used as chiral selective for 20 years. Cyclodextrins (CDs) are cyclic oligosaccharide molecules, which comprise six, seven or eight D(+)-glucopyranose units, assigned the Greek letters, α, β and γ in order. The CDs can form diastereomeric complexes with enantiomers encapsulating the isomers to different extent, producing different stability complexes. CDs can only form strong complexes with those molecules, which shapes and sizes fit well into the cavity of CDs. The CDs are chiral molecules; therefore they act as chiral selective agents. One β-CD molecule has 35 asymmetric atoms, thus it has several possibilities for chiral selective interactions. These chiral centers differ from each other in their spatial and substitution patterns. The broad spectra of CD molecule’s chiral selectivity make them one of the most popular chiral selectivity agents. The overwhelming part of the chiral separations use CDs in GC and CE, but HPLC and SFC applications of them are also frequent.

The authors have long-term practices to use these compounds for chiral separations in various chromatographic techniques.

This presentation shows several examples of the achieved chiral separations of our practices. Particular attention is paid to the determination the relationships between the chiral selectivity and structure of selectands. The chiral purity determination requires minor first elution order in the most cases.

Retention or migration order reversals can be useful in the chiral purity analysis.

Developments of dual cyclodextrin systems are also discussed in CE practice.