Preparation Of Monolithic Capillary Columns And Applications In Electrochromatography

Monolithic capillary column for CEC can be prepared by sintering or in situ copolymerization in a fused-silica capillary. The porous polymer prepared in a capillary can provide supports for separation of analyte with higher phase ratio than open tubular capillary column in CEC. Since the monolithic rod is rigid and directly bonded to the inner wall of the capillary through covalent bonds, no frits are necessary to retain the stationary phase. The production of the monolithic capillary columns for CEC is highly desirable and has become one of the active research subjects in the last few years.In this thesis, the uncharged monolithic capillary columns by in-situ copolymerization of neutral monomers, such as butyl methacrylate, benzyl methacrylate and lauryl metharcylate with ethylene dimethacrylate have been prepared, respectively. A novel capillary monolithic column has also been prepared by in situ copolymerization of 2-(sulfooxy) ethyl methacrylate (SEMA) and ethylene dimethacrylate (EDMA) in the presence of porogens. The characteristics and the performance of these monolithic columns were studied.A mode of capillary electrochromatography (CEC) based on the dynamically adsorption of surfactants on the uncharged monolithic stationary phases has been developed. The ionic surfactant was adsorbed on the surface of polymeric monolith by the hydrophobic interaction, and the ionic groups were towards the running buffer to generate electroosmotic flow (EOF). It is quite convenient to change the direction and magnitude of EOF by changing the concentration of cationic or anionic surfactants in mobile phase. Simultaneous separation of basic, neutral and acidic compounds has been achieved on the developed CEC mode. The mode ofdynamic ion-exchange capillary electrochromatography based on the dynamical modification of a long chain quaternary ammonium cationic surfactant has been obtained for separation of nucleotides. A mode of capillary electrochromatography for separation of ionic compounds driven by electrophoretic mobility on a neutrally hydrophobic monolithic column has also been developed. The peptides at acidic buffer were separated based on their differences of electrophoretic mobility and hydrophobic interaction with the stationary phase, therefore different separation selectivity can be obtained in CEC from that in capillary zone electrophoresis (CZE).A mixed-mode of reversed phase (RP) and strong cation-exchange (SCX) capillary electrochromatography (CEC) based on an anionic monolithic capillary column has been achieved. The capillary monolithic column was prepared by in-situ co-polymerization of 2-(sulfooxy) ethyl methacrylate (SEMA) and ethylene dimethacrylate (EDMA) in the presence of porogens. The sulfate group provided by the monomer 2-(sulfooxy) ethyl methacrylate on the monolithic bed generates an electroosmotic flow (EOF) from anode to cathode, and serves as a strong cation-exchange stationary phase at the same time. A mixed-mode (RP/SCX) mechanism for separation of peptides and basic compounds was observed in the monolithic column, comprising hydrophobic and electrostatic interaction as well as electrophoretic migration at a low pH value of mobile phase.