| Capillary electrochromatography (CEC) is a rapidly developing separation technique which promises high efficiency separations in reasonable periods of time with low solvent consumption. In spite of these advantages, electrochromatography is not commonly used as it is not a practical technique for routine analysis. Our work has focused on making CEC more practical through instrument design and solvent selection.; CEC is a chromatographic technique, thus the general elution problem may be seen when complex samples are analyzed. When the general elution problem occurs, it is impossible to adequately separate all of the solutes in a reasonable period of time using one mobile phase composition. We utilized a flow injection interface for the generation of solvent gradients in CEC. This allows for the resolution of the early eluting solutes while forcing the more strongly retained solutes off the column in a reasonable period of time. This system was shown to reproducibly generate solvent gradients with no significant pressure driven flow.; Next, two power supplies were used to increase the total electrical potential across the capillary. One power supply, operating in positive polarity mode was used to apply potential to the inlet vial. A second power supply, operating in negative polarity mode was used to apply the potential to the outlet vial. The two power supplies were then grounded at separate external ground screws. Experiments proved that the electrical potential was additive across the capillary. Additionally, the noise decreased as neither end of the capillary was ever more than half the total potential from ground. Very high efficiency separations were performed on a long capillary and very fast separations were performed on a traditional length capillary.; Finally, different solvent systems were investigated. First, CO 2/Methanol mixed mobile phases were tested. Unfortunately, the electroosmotic flow (EOF) generated was too slow to be of use in an analytical separation. In contrast, higher viscosity solvents than those traditionally used in pressurized separations were studied. It was found that propanol is a much stronger solvent than methanol, however, the EOF is relatively slow. Ternary mobile phases, where the organic solvent contained equal portions of acetonitrile and propanol, mixed with varying concentrations of water were found to provide the ideal balance of solvent strength and electroosmotic mobility. |
