EFFECT OF ELECTRICAL DOUBLE-LAYER OVERLAP ON THE ELECTROOSMOTIC FLOW IN PACKED-CAPILLARY COLUMNS

A plug electroosmotic velocity profile is generally assumed to be char acteristic of capillary electrochromatography. However, this ideal plu g flow may be illusive in some experiments with packed-capillary colum ns due to overlap of electrical double layers in now channels. We repo rt here a theoretical analysis of the double-layer overlap effects in packed-capillary columns, which is based on Rice and Whitehead's theor y of electroosmotic now combined with a capillary tube model for porou s packing. The results show that the electroosmotic velocity under the influence of double-layer overlap depends strongly on the operating p arameters, which increases with the column porosity, the particle diam eter, and the electrolyte concentration.