Diffusion from emulsion droplets prepared by spraying oil into water

Abstract

A non-intrusive method has been established to monitor the desorption into water of partly water-soluble aromatic compounds from a finely dispersed oil phase, using UV spectroscopy. The emulsion production and method of obtaining diffusion data rely on the properties of an aromatic water-insoluble fluorocarbon which was formulated and synthesized for use as the carrier oil. The oil-in-water emulsions were prepared with different polymeric surfactants and contained either 4-tert-butylacetophenone or anethole as a model active ingredient, which are both sparingly soluble in water. The percentage decrease in the permeability (or mass transfer) coefficient as a result of replacing a PEO–PPO block copolymer (Pluronic F108) by a [PDMS-graft-PEO]–PDMS block copolymer (Tegopren 5843), was on average ca. 70% for emulsions containing 4-tert-butylacetophenone and more than 95% for those containing anethole. Diffusion times for a fractional release of 50% of solute ranged between 6–30 s (anethole/F108) and 24 min (4-tert-butylacetophenone/Tegopren 5843).