Comparative enantioseparation of ketoprofen with trimethylated α-, β-, and γ-cyclodextrins in capillary electrophoresis and study of related selector-selectand interactions using nuclear magnetic resonance spectroscopy.

The enantiomers of ketoprofen were separated by capillary electrophoresis using the (2,3,6-tri-O-methyl)-derivatives of α-, β-, and γ-cyclodextrin (CyD) as chiral selectors. The affinity pattern of the ketoprofen enantiomers toward these CyDs changed depending on their cavity size. Thus, with hexakis (2,3,6-tri-O-methyl)-α-CyD and heptakis (2,3,6-tri-O-methyl)-β-CyD, the R enantiomer of the drug migrated first, whereas the enantiomer migration order was reversed in the presence of octakis(2,3,6-tri-O-methyl)-γ-CyD. The change in the migration order was rationalized on the basis of changes in the structure of the complexes between the ketoprofen enantiomers and the chiral selectors as derived from nuclear magnetic resonance spectroscopy experiments.