Characterization of emulsions and suspensions by video image analysis

The aim of this article is to present a video imaging instrument for rapid and non-intrusive monitoring of the destabilization of dispersed systems such as emulsions or suspensions. Emulsion and suspension destabilization are associated with two main phenomena: gravitational separation (creaming or sedimentation) and particle size variation (coalescence, Ostwald ripening, phase inversion, flocculation). All these phenomena can lead to significant alterations of the final product and it is very important to be able to detect them at an early stage. Our video imaging device coupled with an image analysis software is able to monitor not only the creaming or sedimentation boundary of oil-in-water or water-in-oil emulsions but also the corresponding vertical gray level intensity profiles in the test tube. In addition, the coalescence and the volumes of the creamed, the aqueous and the oil phases can be followed at all times during the ageing of the emulsions. A temperature controlled bath makes it possible to study in situ the effect of temperature on the emulsions. This is particularly useful for finding accelerated ageing processes. Our equipment allows the study of three tubes simultaneously and can also be used for sedimenting systems (e.g. in waste water treatment) or precipitating solution etc. Several examples of applications are given.