Hydrophilic Interaction Stationary Phases Packed Columns And Novel Monolithic Columns For Capillary Electrochromatography

Capillary electrochromatography (CEC) has been considered as a very promising analytical technique that combines the efficiency of capillary zone electrophoresis and the selectivity of liquid chromatography with the use of stationary phases. At present, research works on CEC are mainly focused on both the preparation of columns and its application.CEC separation mode with hydrophilic interaction stationary phases has been established for separation of polar compounds. The retention mechanisms were also systematically investigated, and it was observed that the retention factors of the tested compounds are increased with their polarity. Several types of polar compounds such as peptides, pyridines and basic Pharmaceuticals have been well separated. Furthermore, a method using hydrophilic interaction CEC is also developed for the determination of basic Pharmaceuticals spiked in human serum.CEC separations with mixed-modes of reversed-phase and aniqn-exchange stationary phases was proposed in the capillary monolithic column, which was prepared by in-situ polymerization of 2-(methacryloxy)ethyltrimethylammonium methyl sulfate (MEAMS) and ethylene dimethacrylate (EDMA) in the presence of porogens. The ammonium groups on the surface of the Stationary phase generate an electroosmatic flow (EOF) from cathode to anode, and serve as a strong anion-exchange stationary phase at the same time. Separations of aromatic compounds and basic compounds on the prepared column were performed under the mode of CEC.A zwitterionic monolithic column was prepared for CEC by in-situpolymerization of 2-(dimethyl amino)ethyl methacrylate (DMAM), methacrylic acid (MAA), butyl methacrylate (BMA) and ethylene dimethacrylate (EDMA). So there are two kinds of ionic groups, i.e., amino group and carboxyl group, on the surface of the staionary phase, and the EOF on the prepared column can be easily controlled by changing pH of the mobile phase, and several types of compounds have been successfully separated.A new type of monolithic CEC column based on the urea-formaldehyde resin was prepared, chiral separation of amino acids was achieved by using ligand-exchange interaction under the mode of CEC.