Contribution of electroosmosis to electrorotation spectra in the frequency range of the β dispersion. II. Application to cells with a cell wall

Abstract

The effects of diffusion of ions and of the electroosmotic movement of liquid are included in the high-frequency electrorotation theory of uncharged spherical particles surrounded by a non-conductive membrane and an external conductive shell. This system permits to model cells with a cell wall, and represents an extension of a previous work (Colloids Surf. A 159 (1999) 299) where the cell wall was absent. Moreover, a mistake in the expression for the electroosmotic flow deduced on that work is corrected. In order to formulate the new theory, the field-induced dipole coefficient and volume charge distribution are calculated for the considered system. Special boundary conditions are deduced for these calculations. The results show that diffusive and convective effects lead to a shift in the counter-field rotation peak corresponding to the β dispersion (related to the charging of the membrane), and also reduce its amplitude. This effects are more pronounced for low values of the wall conductivity or for very low values of the internal medium conductivity.