Separation of Enantiomeric Barbiturates by Capillary Electrophoresis Using a Cyclodextrin Containing Run Buffer

In the last few years capillary electrophoresis (CE) was successfully applied to a variety of analytical problems in the field of chiral separations. This article is intended to demonstrate the potential of CE for the determination of enantiomers. The separation is based on the addition of a suitable chiral selector to the buffer. Cyclodextrins perform as excellent selectors forming diastereomeric complexes of different stability with the enantiomeric forms of the analyte. Barbiturates were chosen for chiral electrophoretic separation. They are found in a variety of pharmaceuticals such as sedatives, hypnotics and antiepileptics and are mostly processed as racemic mixtures. Cyclodextrins were applied as chiral selectors. The complex formation depends essentially on the structure of the selector and the analyte, this fact is discussed extensively in the paper. The influence of pH, the type and the concentration of the chiral selector on the separation were investigated. The described experiment offers students an introduction to chiral separations by CE. The simple and fast method development along with the potential to solve difficult analytical problems make CE very attractive.