Possibility of kinetics studies in gradient capillary electrophoresis

The use of capillary electrophoresis (CE) for studying the kinetics of anal ytes chemically reacting or existing in several conformational forms in the longitudinal gradient of the particle electrophoretic velocity is consider ed. The peak parameters for such a 'gradient' CE for the reaction with firs t order kinetics, and for linear dependence of analyte velocity on distance are derived. As the derivations show, the first peak moment and the peak d ispersion depend both on the equilibrium parameters and characteristic reac tion times. Using the '4 sigma' criterion (where the difference of the firs t two peak moments should exceed four times the peak dispersion) of the res olution, the lowest assessable reaction times available are evaluated using the characteristic values of the parameters. These reaction times are abou t 0.01-0.1 s for particle diffusion coefficients of about 10(-7)-10(-5) cm( 2) s(-1), which are surprisingly low compared to reaction times observed by conventional CE techniques used for these aims.