Comparative enantioseparation of talinolol in aqueous and non-aqueous capillary electrophoresis and study of related selector–selectand interactions by nuclear magnetic resonance spectroscopy

Abstract

The enantiomers of the chiral β-blocker drug talinolol were separated with two single component sulfated β-cyclodextrin (CD) derivatives, namely heptakis (2,3-di-O-methyl-6-sulfo)-β-CD) (HDMS-β-CD) and heptakis (2,3-di-O-acetyl-6-sulfo)-β-CD) (HDAS-β-CD), in aqueous and non-aqueous capillary electrophoresis (CE). The enantiomer affinity pattern of talinolol toward these two CDs was opposite in both aqueous and non-aqueous CE. However, the enantiomer affinity pattern for a given CD derivative did not change when aqueous buffer was replaced with non-aqueous background electrolyte. The structures of the analyte–selector complexes in both, aqueous and non-aqueous electrolytes were studied using rotating frame nuclear Overhauser effect (ROESY) NMR spectroscopy. Inclusion complex formation between the enantiomers of talinolol and HDAS-β-CD was confirmed in aqueous buffer, while the complex between the enantiomers of talinolol and HDMS-β-CD was of the external type. The complex of the talinolol enantiomers with HDAS-β-CD in non-aqueous electrolyte was also of the external type. In spite of external complex formation excellent separation of the enantiomers was observed in non-aqueous CE.