Three approaches to enantiomer separation of beta-adrenergic antagonists by capillary electrochromatography

Three different capillary electrochromatographic methods for the enantiomer separation of beta-adrenergic antagonists (acebutolol, alprenolol, atenolol, metoprolol, pindolol, prenalterol, and propranolol) were applied using different cyclodextrins (beta-cyclodextrin, carboxymethyl-beta-cyclodextrin and dimethyl-beta-cyclodextrin) added to the electrolyte, a cross-linked protein-gel (cellobiohydrolase I) and a molecularly imprinted ((R)-enantiomer of propranolol) superporous polymer as chiral selectors. Through use of these different separation strategies, all the beta-adrenergic antagonists studied could be resolved into their enantiomers, although the three methods were carried out without extensive optimization. The protein and molecularly imprinted phases gave the highest selectivities whereas employing cyclodextrins resulted in the highest separation efficiency. Proteins and cyclodextrins are primarily natural products, albeit the cyclodextrins can be derivatized. In contrast, the molecularly imprinted chiral stationary phase can be highly customized when produced.