Behzad Heidarshenas

You need to do an experiment, for example, with mononanosized particles of silicon oxide in the entire pH range where the dispersed system is stable. Draw a graph of the dependence, and then present the dependence in an analytical form. For another dispersed system, this dependence will also be different.

Models have been developed for predicting charge and surface potential for proteins in solution. It requires knowing the pKa constants for the various amino acid residues etc. See my paper on measuring charge of proteins using electrophoretic light scattering in my profile area. If you follow the references, you will learn a lot about the fascinating history going back nearly a century.

zeta potential is highly related to pH