Assessment of oil polarity: comparison of evaluation methods.

In multiple emulsion systems, oily or aqueous transfers may occur between the dispersed droplets through the continuous phase. These transfers are controlled by both the surfactant system (micellar transport), and the partial solubility of one phase in another (molecular transport). The latter could be anticipated from the knowledge of oil polarity, if this information could easily be obtained. In this work, the relative polarity of eight oils used for various purposes has been evaluated from the comparison of their dielectric requirement for solubilization, their interfacial tension and chromatographic analysis. The results showed the complementarities of HPLC analysis and interfacial tension measurements and their superiority over the solubilization method for classifying oils as a function of their polarity.