Phase analysis light scattering correlation for determination of the zeta potential of colloidal systems

Electrophoresis light scattering is a standard technique for measuring the zeta potential of nanoparticles in colloidal systems. However, accurately determining the zeta potential can be challenging, particularly when dealing with small electrophoretic mobilities, which are common in applications such as the separation analysis of drugs and their metabolites. In this paper, we propose a phase analysis light scattering correlation measurement method and derive its basic principle as well. In contrast to the traditional one, the new method extracts the phase signal from two modulated signals obtained by multiplying the detected light signal with the quadrature signals. Then the phase signal is cross correlated with the electric field function to extract the electrophoretic mobility generated by the electric field only. We set up a classic optical arrangement and the experimental results demonstrate the correlation measurement method has a better accuracy, sensitivity and repeatability. We believe this will facilitate the extension of the technique of the electrophoresis light scattering to a wider range of application, especially of the small electrophoretic mobility measurement in the colloidal systems.