Electrochromatography and liquid chromatography : Microtechniques, instrumentation and applications

Abstract: The thesis focuses on the design of efficient chromatographic and electrochromatographic microcolumns where a continuous bed is polymerized in situ in a capillary or a channel in a microchip device. In our technique, a solution of selected monomers is simply sucked or pressed into the capillary or microchip channel for subsequent polymerization. The polymer bed becomes attached covalently to the inner wall concomitantly with the formation of flow-channels in the bed. Consequently, the bed is not packed with beads and no frits are required to support the bed. By using different monomer compositions, including ligand monomers, we have synthesized a wide variety of capillary columns for high-efficiency separations, especially for µHPLC and CEC.Highly resolving continuous polymer beds can be synthesized by using high-power sonication. These beds have been used to separate proteins in the reversed-phase mode by electroosmosis-driven gradient elution.For µHPLC we have designed a pump which affords a constant pulse-free flow in the n1 /min-µl /min range. A water-filled tubular spiral is immersed in a water-bath in which temperature increments can be computer-controlled. When subjected to an applied temperature gradient the water inside the spiral expands. The discharged water acts as a uniformly moving plunger which propels the mobile phase. A pump designed according to this approach has the advantage compared to HPLC piston-pumps and syringe pumps that it does not contain any movable parts and therefore delivers a virtually pulse-free flow also at extremely high pressures.