Separation of isoquinoline alkaloids and saponins by microemulsion electrokinetic chromatography with anionic and cationic surfactants

Isoquinoline alkaloids and saponins are natural products with significant pharmacological effects. Because of the extreme similarity and diversity of their structures, separation of these compounds by capillary electrophoresis (CE) is difficult. A promising separation technique with good separation selectivity and high efficiency, microemulsion electrokinetic chromatography (MEEKC), has been used to separate ten isoquinoline alkaloids and six saponins from Gleditsia sinensis. Anionic and cationic surfactants such as sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) were used as surfactants in MEEKC, on the basis of a series of separation optimizations. For separation of isoquinoline alkaloids comparison of MEEKC with non-aqueous capillary electrophoresis (CE) is discussed with regard to separation efficiency, selectivity, analysis time, and repeatability Study of the separation of the saponins revealed that separation selectivity was different for MEEKC with CTAB and SDS as surfactants; separation with CTAB was much better than that obtained with SDS.