Chiral separation of ephedrines by liquid chromatography using beta-cyclodextrins

beta -cyclodextrins (beta -CDs) have been evaluated as chiral recognition a gents for the enantioseparation of ephedrines by liquid chromatography (LC) . The compounds tested were norephedrine, ephedrine, pseudoephedrine, N-met hylephedrine and N-methylpseuoephedrine. Two possibilities have been invest igated, the employment of a chiral stationary phase consisting of immobiliz ed beta -cyclodextrin, and the addition of the chiral selector to the mobil e phase. In the latter approach the following chiral agents have been assay ed, native beta -cyclodextrin (P-CD), methyl-beta -cyclodextrin (M-beta -CD ), carboxyethyl-beta -cyclodextrin (CE-beta -CD), carboxymethyl-beta -cyclo dextrin (CM-beta -CD) and hydroxypropyl-beta -cyclodextrin (HP-beta -CD). T he experimental factors affecting the chiral separations have been examined , including the percentage of organic solvent, the ionic strength and pH of the buffer, the type and concentration of chiral selector, and the mobile- phase Row rate. Differences in enantioselectivity displayed by the differen t methods are discussed. (C) 2001 Elsevier Science B.V. All rights reserved .