Electroosmotic capillary flow with nonuniform zeta potential

The present work is an analytical and experimental study of electroosmotic now (EOF) in cylindrical capillaries with nonuniform wall surface charge (xi-potential) distributions, In particular, this study investigates perturbations of electroosmotic flow in open capillaries that are due to induced pressure gradients resulting from axial variations in the wall xi-potential. The experimental inquiry focuses on electroosmotic now under a uniform applied field in capillaries with an EOF-suppressing polymer adsorbed onto various fractions of the total capillary length. This fractional EOF suppression was achieved by coupling capillaries with substantially different xi-potentials. The resulting now fields were imaged with a nonintrusive, caged-fluorescence imaging technique. Simple analytical models for the velocity field and rate of sample dispersion in capillaries with axial e-potential variations are presented. The resulting induced pressure gradients and the associated band-broadening effects are of particular importance to the performance of chemical and biochemical analysis systems such as capillary electrokinetic chromatography and capillary zone electrophoresis.