Electrokinetic dispersion in capillary electrophoresis

Abstract

AbstractA “Taylor” dispersion‐type model is developed for the electrokinetic dispersion coefficient of a solute in capillary electrophoresis that accounts for the effects of Poiseuille and/or electro‐osmotic flow of the elutant for the case of low ζ potential. The expression obtained for the height equivalent of a theoretical plate is compared with experimental results reported in the literature for the case of neutral, nonretained solutes propelled by electro‐osmotic flow. The results further reveal some interesting and somewhat unexpected interactions of the electro‐osmotic and Poiseuille components of the elutant flow. Superposition of Poiseuille flow on the natural electro‐osmotic flow allows greater freedom in the choice of elutant velocity, without necessarily increasing the dispersion. In fact, it results in lower dispersion under some conditions. Optimum flow conditions are obtained for minimizing the plate height or, equivalently, for maximizing the Peclet number.