COMPARISON OF 3 ELECTROKINETIC METHODS TO DETERMINE THE ZETA-POTENTIAL OF SOLID-SURFACES

The aim of this work was to compare informations obtained on surface e lectric charge of solids using three different methods based on electr okinetic phenomena study. These methods were microelectrophoresis, whi ch only applies to particles, electro-osmosis, useful on flat plate sp ecimens, and streaming potential, which applies either to particles an d macroscopic samples. Two model materials were used, glass and poly(m ethylmethacrylate), in contact with 10(-2) mol.l(-1) potassium nitrate , from pH 2 to 9. For each material, under the form of particles or pl ates, the three methods gave similar profiles of the pH-dependant zeta potential curves and very close isoelectric points, so that global in formations obtained were the same. However, numerical values of zeta p otential differed from one method to another. Results suggest that the se deviations are related to the location of the shearing plane within the electrical double-layer.