THEORETICAL RELATION BETWEEN THE ZETA POTENTIAL AND THE BACKGROUND ELECTROLYTE COMPOSITION IN CAPILLARY ELECTROPHORESIS.

CLAUDIO L. A. BERLI, MARIA V. PIAGGIO, JULIO A. DEIBER

Foz do Iguazu, Brasil

Congreso; 11th International Conference on Surface and Colloid Science; 2003

International Association of Surface and Colloid Scientists

Capillary zone electrophoresis (CZE) is one of the separation modes most commonly used in capillary electrophoresis, mainly because the magnitude of the electroosmotic flow (EOF) can be manipulated to optimize the separation performance through appropriate changes of applied electrical field, capillary zeta potential and electrical permittivity-to-viscosity ratio of the background electrolyte (BGE). In particular, the main factor determining the electrokinetic potential is the BGE composition. In this work, a theoretical relation between the zeta potential and the composition of the BGE to be used in CZE is presented. This relation is derived on the basis of Poisson-Boltzmann equation and considering the equilibrium dissociation of acid groups at the capillary wall as the mechanism of charge generation. The model involves the relevant physicochemical parameters of the BGE-capillary interface. The BGEs considered are either salt or/and buffer solutions. The model is successfully applied to EOF experimental data for different capillaries and aqueous solutions, covering a wide range of pH and ionic strength. Numerical predictions are also presented showing the capability of the model to quantify the EOF.