What Is Zeta Potential

In instruments using electrophoretic light scattering, a sample is subjected to light while its particles move under the influence of an oscillating electric field. Analysis of shifting wavelength, or doppler shift, in the resulting scattered light allows determination of electrophoretic mobility – from which zeta potential can be calculated.

Zeta potential can be described in a number of ways. Some refer to it as the electrokinetic potential in colloidal systems. Others describe it as a measure of the electrostatic (or charge) repulsion/attraction between particles.

Looking at the relationship between particles and their medium in more detail, zeta potential can be defined as the potential difference between a dispersion medium and the stationary layer of fluid attached to a dispersed particle. However it is described, zeta potential is essentially a useful indicator of the effective charge in solution.

More important than its definition is the significance of its measured values. For example, colloids with a high zeta potential will tend to be stable. Those with a low zeta potential are more likely to coagulate or flocculate.

The nature and behaviour of suspensions is heavily influenced by particle size as well as zeta potential, so it very useful to be able to measure these parameters at the same time. Zeta potential is, in turn, affected by the nature of the solvent used.

Knowledge gained from measuring zeta potential allows the performance of various combinations of material, particle size and dispersal medium to be predicted, to a large extent, so that valuable time is not wasted in needless testing of formulations that are not compatible.

Important applications of this knowledge can be found in pharmaceutical development, medical research, water management and mineral processing, to name but a few sectors. With such a diversity of materials and solvent conditions to handle, instrumentation designed to measure zeta potential needs to be highly flexible.