If I am not wrong, before Zeta analyzers came into play, researchers used to depend on electrophoretic mobility experiments to estimate the surface potential of nanoparticles. I would like to know more about it.
Electrophoretic mobility, surface potential and zeta potential are related but they are not the same. Most zeta analyzers measure electrophoretic mobility. Then, based of different approaches (Smoluchowsky, Henry) they calculate zeta potential.
You will get more information in the classic book
"Zeta potential in colloid science" by Robert Hunter
Juan Sir, Thank you so much, I will refer that book for further detailed information. And Sir, surface potential and zeta potential are same only when the suspended medium has no net charge i.e, electrically neutral, Am I right ?
Zeta potential is the potential at the shear plane (this plane is usually identified with the outer Helmotlz plane). Most people identify zeta potential with surfece potential. This is not correct. However, most time the error you make with this approximation is less than the experimental and may be acceptable.