Chiral recognition of verapamil by cyclodextrins studied with capillary electrophoresis, NMR spectroscopy, and electrospray ionization mass spectrometry

Capillary electrophoresis (CE) allows the observation of the opposite affin ities of the enantiomers of (+/-)-verapamil [2-isopropyl-2, 8-bis (3, 4-dim ethoxyphenyl)-6-methyl-6-azaoctannitrile, VP] toward beta-cyclodextrin (bet a-CD) and heptakis(2,3,6-tri-O-methyl)-beta-CD (TM-beta-CD). In addition, i n the presence of beta-CD in the background electrolyte, longer migration t imes and lower separation factors were observed compared to TM-beta-CD. The binding constants of (+)- and (-)-VP with beta-CD and TM-beta-CD determine d using C-13 NMR spectroscopy explain the results observed in CE. Electrosp ray ionization mass spectrometry (ESI-MS) was used as an alternative techni que for the characterization of VP-CD complexes. (C) 1999 Wiley-Liss, Inc.