Chiral Separation Enhancement in Capillary Electrophoresis by Electrophoretic Mobility Differences without Electroosmosis

To improve separation efficiency and address the adverse effects of electro-osmosis, a coated capillary was used to shield the electroosmosis. A nanoflow pump was used to control the flow of the electrophoretic medium, thereby extending the time of the electrophoretic action. Furthermore, by using a coated capillary that is only 10 cm long as the separation column, the electric field strength could reach as high as 250 V/mm. These strategies strengthened the interaction between the enantiomers and the chiral selector, thus enhancing the resolution of enantiomers. As a result, complete separation of the amlodipine enantiomers could be achieved by halting the electrophoretic medium. Further extending the duration of flow stoppage can increase the resolution several-fold. The method established in this study exhibits excellent accuracy and precision. Despite experiencing a long period of flow stoppage, the relative standard deviations of both migration time and resolution remain less than 2%. This method not only remarkably enhanced the resolution of amlodipine enantiomers but also demonstrated broad applicability in separating other chiral enantiomers, particularly for those substances that are difficult to separate using conventional capillary electrophoresis.