Possibility of kinetics studies in gradient capillary electrophoresis

Abstract

The use of capillary electrophoresis (CE) for studying the kinetics of analytes chemically reacting or existing in several conformational forms in the longitudinal gradient of the particle electrophoretic velocity is considered. The peak parameters for such a ‘gradient’ CE for the reaction with first order kinetics, and for linear dependence of analyte velocity on distance are derived. As the derivations show, the first peak moment and the peak dispersion depend both on the equilibrium parameters and characteristic reaction times. Using the ‘4σ’ criterion (where the difference of the first two peak moments should exceed four times the peak dispersion) of the resolution, the lowest assessable reaction times available are evaluated using the characteristic values of the parameters. These reaction times are about 0.01–0.1 s for particle diffusion coefficients of about 10^–7–10^–5 cm² s^–1, which are surprisingly low compared to reaction times observed by conventional CE techniques used for these aims.