Similar qualitative and quantitative o/w/o and w/o emulsions: Improvement of cosmetic properties

The aim of this study was to compare o/w/o multiple emulsions with w/o simple emulsions in terms of occlusivity and remanence. Firstly, fourteen o/w/w multiple emulsions were prepared with w/o emulsion components. Several parameters were optimized i.e. primary emulsion/multiple emulsion ratio, concentration of the emulsifiers, mixing speed. The yield and stability of the preparation were measured by a tracer release method using phthalic acid diethyl ester. This tracer, introduced in the inner oily phase, was chosen according to general requirements : a high oil/water diffusion coefficient, good stability under various pH and temperature,and easy detection. From entrapment yield and droplet breakdown curves calculated from the tracer UV spectrophotometric data, one emulsion was selected for comparison with the w/o emulsion. Skin oil level measurements with a sebumeter provided efficient data to evaluate the remanence. Occlusivity was measured by the gravimetric method of water loss with gelatin cells. The remanence improved significantly, since the occlusivity properties were retained. As the total percentage of oil was the same within the two emulsions, the increase of remanence is mainly due to the galenic form.