Symmetric electrophoretic light scattering for determination of the zeta potential of colloidal systems

We present a symmetric electrophoretic light scattering measurement method for the determination of the zeta potential of colloidal systems. In contrast to the traditional method, where a detector probes the light from one scattering point and a reference, this method takes two symmetrical points at the vertical arms on both sides of a u-shaped sample pool as detection points, where the magnitude of the speed of the particles is almost the same except that the directions are opposite. We derive the light intensity autocorrelation function, and observe that the frequency of the signal for the velocity measurement is doubled, which results in a high signal-to-noise ratio. We set up a double scattered optical arrangement and the experimental results demonstrate that the symmetric measurement method has a better accuracy, sensitivity and repeatability than those of the traditional method. It is expected that this symmetric measurement method will improve the determination of the zeta potential of colloidal systems.