Phase diagram studies of microcapsule formation using hydroxypropyl methylcellulose phthalate

Abstract

Microcapsules of hydroxypropyl methylcellulose phthalate were prepared using a non-aqueous emulsion method. The study was designed to determine the region of microcapsule formation in the ternary system of mineral oil, acetone and polymer and to present the data by means of phase diagrams. Increasing amounts of sorbitan monooleate were added to mineral oil to determine the effect of surfactant concentration on the phase diagram. The effect of sorbitan monooleate, sorbitan trioleate and sorbitan monolaurate on the microcapsule region of the phase diagram was also investigated. Particle size analysis was carried out to determine if the concentration and type of surfactant used had a significant effect on the size of the microcapsules obtained. Tartrazine was encapsulated as a model drug and its dissolution was studied in acidic and neutral mediums. The results indicate that the addition of sorbitan monooleate increased the microcapsule region of the phase diagram and sorbitan trioleate had a similar effect. However, the microcapsule region in the phase diagram decreased when sorbitan monolaurate was used. The particle size increased with increasing concentration of polymer, irrespective of the type and concentration of surfactant used.