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The validity of the Smoluchowski equation in electrophoretic studies of lipid membranes
Author(s) -
Egorova Elena M.
Publication year - 1994
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.11501501170
Subject(s) - smoluchowski coagulation equation , electrophoresis , zeta potential , chemistry , dimensionless quantity , charge density , surface charge , concentration polarization , membrane , ionic strength , polarization (electrochemistry) , vesicle , analytical chemistry (journal) , chemical physics , thermodynamics , chromatography , classical mechanics , materials science , physics , nanotechnology , quantum mechanics , nanoparticle , biochemistry , aqueous solution
The Helmholtz‐Smoluchowski theory, widely used for the calculation of zeta potential from the measured electrophoretic mobility (EPM), is known to be invalid in the region where the mobility is affected by the surface conductivity and polarization of the electrical double layer. In this region, the zeta potential found according to the Smoluchowski equation (ζ sm ) is not identical to the true electrostatic potential at the hydrodynamic plane of shear (ζ) which is considered in the Gouy‐Chapman‐Stern theory of the electrical double layer. As a result, ζ sm cannot be used for the subsequent calculation of surface potential and surface charge density of a membrane studied. Here we suggest a simple way, allowing one to decide between the validity and nonvalidity of the Smoluchowski equation in various sets of experimental conditions used in electrophoretic measurements on lipid membranes. We calculated the dimensionless criterion Rel , accepted in the Dukhin theory of electrophoresis as a measure of the extent of the influence of surface conductivity and double layer polarization on EPM. The Rel changes, with membrane charge density, ionic strength and vesicle radius, were found to be helpful in finding the combinations of these three parameters, corresponding to the validity of the Smoluchowski equation.