USING ELECTROPHORESIS TO DETERMINE ZETA POTENTIAL OF MICELLES AND CRITICAL MICELLE CONCENTRATION

A heterodyne laser Doppler electrophoresis method for measuring the zeta potential of a surfactant micelle has been developed. Details of the method and results obtained will be presented in this paper. In comparison with the tracer electrophoresis method used in determining the zeta potential of a surfactant micelle, this method is much time saving and less laborious. The zeta potential values of one anionic and three cationic surfactant micelles have been determined by using this method. From the zeta potential versus concentration curve, one can determine the micellar dissociation concentration and the critical micellar concentration of a surfactant. The values obtained agree quite well with the surface tension measurement. The surfactant systems were studied in the presence and absence of NaC1 The zeta potential appears to decrease with the increase of NaC1 concentration.