CONTRIBUTION OF THE ELECTROOSMOTIC FLOW TO PEAK BROADENING IN CAPILLARY ZONE ELECTROPHORESIS WITH UNIFORM ZETA-POTENTIAL

An expression is derived which gives the plate height contribution caused by an electroosmotic flow (EOF) in a cylindrical capillary with longitudinally uniform zeta potential. The derivation is made in terms of effective thickness of the electric double layer (an analogue to the Debye length). Typical values of the effective thickness calculated for common situations are given. The resulting expression for the plate height, H-eo = beta(2)v(eo)/D, enables one to calculate the plate height simply as a function of the diffusion coefficient, D, of the solute, the electroosmotic velocity, v(eo), and the thickness of the electric double layer, beta. The impact of peak broadening by the EOF is compared with that from longitudinal diffusion and extra-column effects for solutes with widely varying diffusion coefficients.