Selectivity Tuning in Pressurized Capillary Electrochromatography with a Zwitterionic Monolithic Column

A polymethacrylate-based capillary monolithic column with zwitterionic functional groups was prepared by an in situ copolymerization method. The column was used in pressurized capillary electrochromatography (pCEC) for the separation of a test mixture of basic, neutral and acidic analytes. Unique manipulation of selectivity in pCEC was demonstrated by fine-tuning the applied voltage. The separation mechanism for neutral compounds was primarily attributed to hydrophilic interaction, whereas the separation mechanism for charged compounds was attributed to electrophoresis. Due to the multiple retention mechanisms, the pCEC system using a zwitterionic monolithic column showed better separation of the mixture consisting of neutral and charged molecules than capillary liquid chromatography with an identical column.