ELECTROCHROMATOGRAPHY AND MICRO HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH 320-MU-M ID PACKED-COLUMNS

Electrochromatography is a chromatographic method in which the mobile phase (liquid or supercritical fluid) is ''pumped'' through a stationa ry phase in a microbore or capillary column by electroosmosis using an electric field. The technique permits separation of charged and uncha rged compounds with higher resolution and superior efficiency when com pared with micro-HPLC with an identical column. It is desirable to wor k with packed capillary columns with wide diameter in electrochromatog raphy in order to improve detectability and column loadability. This s tudy shows that we have moved a step forward towards this goal in spit e of problems and difficulties, due to Joule heating, frit making and column packing in using wide-diameter columns. The paper demonstrates that the pressure pump of micro-HPLC with a commercially available 320 mu m I.D. column can be replaced by the electroosmotic ''pump'' of ca pillary zone electrophoresis. Experiments were carried out in a chroma tographic system under both electroosmosis and pressure-driven flow wi th 320 and 50 mu m I.D. columns packed with 3- and 5-mu m ODS. The adv antage of electrochromatography over conventional micro-HPLC is shown.