Usefulness of methylated-β-cyclodextrin-based buffers for the separation of highly hydrophobic solutes in non-aqueous capillary electrophoresis: Application to the separation of derivatized phytosterols

Abstract

This study describes the capillary electrophoretic separation of highly hydrophobic non-UV absorbing solutes in non-aqueous background electrolyte solution containing neutral cyclodextrins. After a derivatization step, several positively charged derivatives of neutral phytosterols have been partially resolved using a non-aqueous acidic electrophoretic buffer consisting of 20 m M ammonium acetate dissolved in methanol–acetonitrile–acetic acid (50:49:1, v/v). The selectivity has been significantly improved by the addition of 10 m M heptakis(2,6-di- O-methyl)-β-cyclodextrin to the non-aqueous buffer in order to promote hydrophobic interactions to differentiate similar structural molecules. Such non-aqueous buffers will be suitable to capillary electrophoresis–mass spectrometry coupling.