INFLUENCE OF ELECTROLYTE-COMPOSITION ON THE EFFECTIVE ELECTRIC-FIELD STRENGTH IN CAPILLARY ZONE ELECTROPHORESIS

In capillary zone electrophoresis the electrophoretic velocity of an i on decreases as the concentration of the background electrolyte soluti on is increased. This is caused by changes in the electrophoretic mobi lity of the ion (mu(ep)) as well as by changes in the net force affect ing it, namely the effective electric field strength (E(eff)). The ele ctrophoretic mobility of an ion is altered through changes in absolute viscosity of the electrolyte solution and changes in the solvated siz e of the ion. E(eff) is altered mainly by changes in the magnitude of the charge asymmetry effect and the electrophoretic effect, both of wh ich retard the motion of ions. In this study, the three-marker techniq ue was used to study the effect of background electrolyte concentratio n (0.02-0.08M 3-[cyclohexylamino]-1-propanesulfonic acid and counter i on (Li, Na, K, and Cs) on E(eff). It was found that the concentration of the background electrolyte markedly affects E(eff) and that E(eff) approaches E as the concentration of the background electrolyte approa ches zero. The counter ion had a minor effect on E(eff): as the size o f the hydrated radius of the counter ion increased, E(eff) decreased. The three-marker technique proved to be efficient for such determinati ons.