Preparation And Characterization Of Zwitterionic Monolithic Column For Capillary Electrochromatography

Capillary electrochromatography (CEC) is a relatively new micro-separation technique that combines the high efficiency of capillary electrophoresis and the high selectivity of high performance liquid chromatography. Accordingly, it has attracted more and more attention in recent years. Currently monolithic columns are considered as the most suitable stationary phases for CEC due to their simple preparation procedures, unique properties and no need for frits, and it has been highlighted to develop new monolithic columns in the research on CEC. However, the vast majority of previous reports on CEC only concern the monolithic stationary phases charged positively or negatively, with EOF directions unchangeable and separation mechanisms simple.In this thesis, a new zwitterionic monolithic column for CEC was prepared by in-situ radical polymerization of glycidyl methacrylate (GMA) and dimethacrylate (EDMA) followed by derivation with L-lysine, which can be used for separations based on various separation mechanisms with the direction and magnitude of EOF changeable. The effects of polymerization conditions on column performances were experimentally examined, and the optimal conditions for preparing the columns were established. After optimizing several separation conditions, several inorganic anions and several anilines were baseline separated respectively on identical column, and the possible separation mechanisms were discussed. It was also predicted that this column has a good potential to use for separating bio-molecules such as amino-acids, poly-peptides, proteins or the transition metal ions based on the separation mechanisms of hydrophobic interaction, electrostatic interaction and complex interaction between the analytes and the stationary phase.Ultraviolet-visible spectrometry is the detection method most commonly used for CEC currently. However, this detection method suffers from poor sensitivity due to the limited optical path length of flow cell on the capillary and easy breakage at the detection window because of no polymer coating there. In the present work, a homemade flow cell of U-shape was used for prolonging the optical path length, and consequently modifying the sensitivity. Also a simple method for coupling the U-shaped flow cell and the capillary monolithic column with the dead volume nearly zero was established, and thus the problem of easy breakage with the column can be resolved by simply replacing the broken flow cell with a new one.