Monitoring the stability of emulsions by optical microscopy

Emulsions are defined as thermodynamically unstable systems of two or more immiscible liquids in which one phase is dispersed in another. Stability of emulsion refers to the ability of emulsions to resist changes in physicochemical properties over a period of time. Destabilization of emulsions can occur as gravitational separation (creaming / sedimentation), flocculation, coalescence, phase inversion and Ostwald ripening. Factors affecting the stability of emulsions are preparation conditions, the composition of the emulsion and the properties of the dispersed phase (concentration and size of droplets, droplet charge, interactions). The fastest and cheapest method of stability monitoring is visual monitoring of the separation of the emulsion’s phases. However, the stability of emulsions containing droplets smaller than 100 μm can't be detected visually. Optical microscopy is widely used as a simple technique that allows monitoring of the stability of emulsions, size and distribution of droplets in the emulsion over a long period of time. In this way the destabilization can be monitored by visual observation of the size of droplet and phase separation. In this work, the stability of prepared emulsions was monitored using optical microscopy by taking samples from the top, middle and bottom of the container and observing the stability at 10x and 20x magnification over some period of time.