Selectivity manipulation using nonaqueous capillary electrophoresis. Application to tropane alkaloids and amphetamine derivatives

Non-aqueous capillary electrophoresis was investigated for its potential in the analysis of pharmaceutical compounds, namely tropane alkaloids and amp hetamine derivatives. The separation of these drugs was compared in aqueous and organic media such as methanol and/or acetonitrile. Selectivity, migra tion times and efficiency were critically affected by the composition of th e methanol/acetonitrile mixture, as well as by the nature and the concentra tion of the electrolyte. In particular, the migration orders of two positio nal isomers, littorine and hyoscyamine, were inverted in the presence of tr ifluoroacetic acid in the nonaqueous medium. The same behavior was observed for amphetamine-methamphetamine and for two methylenedioxyamphetamine deri vatives.