Aqueous and Non‐aqueous Capillary Electrophoresis of Pharmaceutical Amines*

Abstract

A lipophilic pharmaceutical amine, pKa of 8, and its analogues were analysed by aqueous and non-aqueous capillary electrophoresis (CE). The effect of different organic solvents on electrophoretic performance was also investigated. Wall adsorption was tremendously reduced when acetonitrile was used instead of water. Peak symmetry and efficiency were greatly improved as a direct result, and migration times were significantly shorter. Relative standard deviations on corrected areas were less than 1% with use of an internal standard. Selectivity and electroosmotic flow were greatly affected by the type of organic solvent used. Ammonium acetate (25 mM), acetic acid (1m), methanol-acetonitrile (50:50v/v) buffer offered the best compromise in terms of migration time, efficiency and resolution. Non-aqueous CE was found to have significant advantages over aqueous CE for the analysis of pharmaceutical amines, offering enhanced selectivity, rapid analysis and an increase in signal-to-noise ratio.