Effects of compositions of dimethyl-beta-cyclodextrins on enantiomer separations by cyclodextrin modified capillary zone electrophoresis

In enantiomeric separation by capillary zone electrophoresis using dimethyl -beta-cyclodextrin (DM-beta-CD) as a chiral selector, enantioselectivities were sometimes significantly different among DM-beta-CDs from five differen t suppliers. The reason was due to the difference in the compositions among these commercial products, which was shown by the liquid chromatographic ( LC) analysis. As for commercial DM-beta-CD from one supplier, two major com ponents were obtained by preparative LC. NMR spectroscopic and mass spectro metric analyses of these two components were performed to estimate the stru cture of each component. The results implied that the commercial products c onsist of heptakis(2,6-di-O-dimethyl)-beta-CD and hexakis(2,6-di-O-methyl)- mono(2,3,6-tri-O-methyl)-beta-CD. Sometimes different enantioselectivities were observed between these two components including the original DM-beta-C D. (C) 1998 Elsevier Science B.V. All rights reserved.