Stochastic simulation of laminar and electroosmotic convection in capillary electrophoresis and electrochromatography

A stochastic (Monte Carlo) simulation has been utilized to study the combination of laminar and electroosmotic convection under typical conditions for capillary electrophoresis and electrochromatography. The radial velocity profiles are determined for varying proportions of laminar and electroosmotic flow at a constant linear velocity. In addition, the molecular zone profiles and the corresponding statistical moments are established for nonretained and retained solutes. It is found that the radial velocity profile has significant influence for solutes that are not retained by a stationary phase, including those separated by electrophoresis alone. However, this effect is rapidly diminished such that retained solutes with an absorption coefficient as small as 0.1 show little influence if their diffusion coefficients in the mobile phase are on the order of 1.0 x 10(-5) cm2/s. Larger solutes with diffusion coefficients of 1.0 x 10(-6) cm2/s or less show slightly greater variance and asymmetry. In most cases, however, slow kinetics and resistance to mass transfer in the stationary phase exceed that in the mobile phase. As a consequence, there is little effect of the radial velocity profile for retained solutes.