| Continuous-bed columns containing a wall-supported continuous bed have shown great potential for capillary electrochromatography (CEC) due to the inherent advantages: high sample capacity, high column bed stability, and the absence of end-frits. In this dissertation, a new continuous-bed column containing sol-gel bonded packing materials in a fused silica capillary was developed. The properties of continuous-bed columns containing sol-gel bonded packing materials in CEC were explored.; The fused silica capillary was packed with porous packing materials using a CO2 slurry. The packed column was partially filled with a non-viscous siliceous sol formed by hydrolysis and polycondensation of tetramethoxysilane and ethyltrimethoxysilane. After gelling and aging of the sol at room temperature, the column was flushed with supercritical CO2 and then dried at elevated temperature while the column was continuously purged with supercritical CO2. The non-bonded packing materials were flushed out after the column was dried, and a detection window was fabricated immediately after the column bed using concentrated ammonium hydroxide to dissolve away the polyimide coating. Scanning electron microscopy of a cross-section of the capillary column revealed that the packing materials were bonded to each other and to the column inner wall by the sol-gel, forming a wall-supported continuous bed. Continuous-bed columns of 50--100 mum i.d. containing sol-gel bonded small-pore octadecylsilica (ODS), large-pore ODS, and small-pore ODS with built-in sulfonic acid groups (ODS/SCX) were successfully prepared.; The performances of these continuous-bed columns were evaluated for CEC using small neutral molecules with TRIS or phosphate buffer in aqueous acetonitrile mobile phase. No bubble formation was observed during CEC operation. Different from columns containing sol-gel bonded ODS, columns containing sol-gel bonded mixed-mode ODS/SCX generated nearly pH independent electroosmotic flow over pH 2--9. Columns containing Sol-gel bonded large-pore ODS produced more than twice the efficiencies of those containing small-pore ODS. Efficiencies of 410,000 plates per meter and 180,000 plates per meter were obtained for non-retained thiourea from columns containing sol-gel bonded (3 mum, 1500 A ODS) particles and sol-gel bonded (3 mum, 80 A ODS) particles, respectively. |
