Zeta potential is a function of both the particle surface and the dispersant medium. It is an important predictor of electric or charge stabilization and can also be used to identify the adsorption of non-ionic or steric layers. In short, zeta potential provides key information about the interfacial behavior of multicomponent formulated products.

Particles acquire a surface charge when exposed to a polar medium like water. There are many origins of this surface charge depending upon the nature of the particle and it’s surrounding medium. Typically, materials in water are negatively charged but there are some materials that are positively charged. An isoelectric point (IEP), is the pH at which a molecule or material carries the average nett charge of zero. The IEP can affect the solubility of a molecule at a given pH. Materials typically have minimum stability or minimal solubility in water or salt solutions at the IEP and often coagulate or precipitate out of solution at this pH. The IEP also indicates the acidity and alkalinity of the material. Again, the zeta potential is affected by both the particulate, or dispersed phase, as well as the dispersion medium. Zeta potential is important in evaluating product consistency, product quality and final product performance.

In this presentation, we will discuss zeta potential measurements, zeta potential theory, charging mechanisms that affect surface interfacial behavior and isoelectric point determination.