The zeta potential is a key parameter that affects the stability of colloidal systems. It is a measure of the electrical charge on the surface of colloidal particles, which can be either positive or negative. The zeta potential plays a crucial role in determining the degree of repulsion or attraction between particles in a colloidal dispersion, which in turn influences the stability of the system.In a stable colloidal system, the particles are well-dispersed and do not aggregate or settle out. This is achieved when the zeta potential is sufficiently high either positive or negative , leading to a strong repulsive force between the particles. This repulsion prevents the particles from coming too close to each other, thus avoiding aggregation and maintaining the stability of the system.On the other hand, if the zeta potential is low close to zero , the repulsive forces between the particles are weak, and the attractive forces such as van der Waals forces dominate. This can lead to aggregation or flocculation of the particles, causing the colloidal system to become unstable and eventually settle out or separate.Experimentally, the zeta potential can be measured using a technique called electrophoretic light scattering ELS or laser Doppler velocimetry LDV . In this method, a colloidal sample is subjected to an electric field, causing the charged particles to move towards the oppositely charged electrode. The velocity of the particles is proportional to their zeta potential, and it can be determined by analyzing the scattered light from a laser beam that passes through the sample.By measuring the zeta potential of a colloidal system, one can gain insights into the stability of the system and optimize the formulation or processing conditions to achieve the desired stability. This is particularly important in industries such as pharmaceuticals, cosmetics, food, and materials science, where the stability of colloidal systems plays a critical role in product performance and shelf life.