The van Deemter plots for CEC and HPLC differ, as the minimum of the CEC plot is smaller and flatter These smaller plate heights are generally attributed to the plug flow of CEC (Figure). Since, in CEC, the flow variation between channels is smaller, the eddy diffusion is substantially lower. n addition, the particles in the bed do not hinder the flow, as they do in HPLC but propel the liquid through the column, as the EOF originates at the particle surface. Since there is no pressure drop over the column in CEC it is possible to use much smaller particles and longer columns than in HPLC. The efficiency can therefore be even greater, as both A terms and C terms in the van Deemter equation decrease with the smaller particle diameters. The A term in on (13) relates to the diffusion arising from different flow paths that solute molecules can take through the packed bed. Due to the laminar flow in HPLC in contrast to plug flow in CEC solite molecules between streams mov at different velocities. However, in CEC the contribution of eddy diffusion to band broadening is significantly lower because the velocities between the channels are identical. lt clear from the van Deemter equation (Equation (13) that a reduction in the particle diameter will lead to more densely packed and uniform columns and in turn a smaller contribution from the A term. The C-term reflects band broadening due to slow equilibration of the solutes resistance to mass transfer between the mobile and stationary pha and is increased as the ses ase velocity increases because less time is available for equilibration. The contribution to band broadening from the C-term also can be reduced by the use of smal diameter packing materials. The effect of particle s on efficiency, when comparing pressure- driven and electro-driven flow has been investigated by Knox and Grant, indica ng that smaller particle sizes produce higher efficiencies. The effect of particle size has also been investigated