Comparative electrophoretic mobility and streaming current study for ζ-potential determination

The main purpose of this work is to compare the xi-potential obtained from streaming current and electrophoretic mobility measurements. The electrokinetic experiments were performed using two anionic polystyrene latexes whose surface charge density and average particle diameter were -9.8 and -3.4 mu C cm (-2) and 0.65 and 1.2 mu m, respectively. For the conversion two theories were used, the Levine et al. theory for the streaming current and O' Brien-White for the electrophoretic mobility measurements. This way most of the phenomena taking place at the interface are taken into consideration. The xi-potentials obtained this way compare well for the largest latex with the lowest: surface, charge. However, there are substantial discrepancies for the smaller latex sample with the higher surface charge density. These discrepancies are discussed in terms of the effect of the surface conductance on the electrokinetic signal. (C) 1999 Elsevier Science B.V. All rights reserved.