title: Electrophoretic mobility of a spherical colloidal particle in a salt-free medium.
abstract: A general expression as well as approximate expressions are derived for the electrophoretic mobility of dilute spherical colloidal particles in a salt-free medium containing only counter ions. It is shown that there is a certain critical value of the particle surface charge. When the particle surface charge is lower than the critical value, the electrophoretic mobility is proportional to the particle surface charge or the particle zeta potential, following Hückel's formula. When the particle surface charge is higher than the critical value, the electrophoretic mobility becomes independent of the particle surface charge. This is due to the effect of counter ion condensation in the vicinity of the particle surface.
authors.affiliation: Faculty of Pharmaceutical Sciences and Institute of Colloid and Interface Science, Science University of Tokyo, 12 Ichigaya Funagawara-machi, Shinjuku-ku, Tokyo, 162-0826, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ohshima
mesh_terms: D003102:Colloids / Q000737:chemistry*; D004586:Electrophoresis; D007477:Ions / Q000737:chemistry; D008956:Models, Chemical; D010316:Particle Size; D012680:Sensitivity and Specificity; D013499:Surface Properties
chemical_list: D003102:Colloids; D007477:Ions