Experiences with packed capillary electrochromatography at ambient pressure

The practical execution of packed capillary electrochromatography is evaluated. The most serious problem is the generation of air bubbles in the system. This occurs especially in frits which were fabricated by glueing particles differing from the packing particles. No air bubbles were generated with frits which were prepared by locally sintering a narrow band of the reversed-phase packing by means of a heating filament, while flushing the column with water. In this way electrochromatography can be performed simply without pressurizing the buffer vials, providing the mobile phase is frequently degassed with helium. The performance under electrically driven conditions appears to be excellent and for 5 mu m reversed-phase particles reduced plate heights down to 1.8 were achieved. Compared to pressure driven conditions, 25-40% smaller plate heights were obtained under electrically driven conditions.