Enantioseparation of atropine by capillary electrophoresis using sulfated beta-cyclodextrin: application to a plant extract

A capillary zone electrophoresis (CZE) method, with sulfated P-CD as chiral selector, was optimized by means of an experimental design for the enantio separation of atropine. In this study, a central composite design was used and the following factors were varied simultaneously: buffer concentration, buffer pH and sulfated P-CD concentration. The resolutions between littori ne and its positional isomer ((-)-hyoscyamine) and between atropine enantio mers, as well as the separation time and generated current were established as responses. A model was obtained for each response by linear multiple re gression of a second-degree mathematical expression. The most favorable con ditions were determined by maximizing the resolution between atropine enant iomers and by setting the other responses at threshold values. Successful r esults were obtained with a 55 mM phosphate buffer at pH 7 in the presence of 2.9 mM sulfated-beta-CD at 20 degrees C and 20 kV. Under these optimized conditions, a baseline separation of littorine and atropine enantiomers wa s achieved in less than 5 min. Finally, the method allowed the enantiomeric separation of atropine in a pharmaceutical formulation and was also found to be suitable for the enantiomeric purity evaluation of (-)-hyoscyamine in plant extracts, in relation with the extraction procedure. It was demonstr ated that supercritical fluid extraction induced less racemization than cla ssical liquid-solid extraction procedures. (C) 2000 Elsevier Science B.V. A ll rights reserved.