Physical factors affecting microencapsulation by simple coacervation of gelatin.

Gelatin has been coacervated at 60 degrees C using sodium sulphate. Interfacial tensions between coacervate and supernatant liquid, coacervate and two oils (with and without one of two drugs, clofibrate and chlormethiazole) and supernatant liquid and the oils (+/- drug) have been measured by a drop volume technique, in the presence and absence of one of three surfactants, cetrimide, sodium lauryl sulphate and hexadecyltrimethylammonium lauryl sulphate (double salt). Spreading coefficients calculated from tensions indicate that coacervate should spread readily over oil droplets in presence of double salt, less readily with cetrimide and spreading is unlikely in the presence of sodium lauryl sulphate. The sign of the charge on coacervate droplets and oil droplets was identified under different conditions and showed coacervate droplets and oil droplets have opposite charges except in the presence of sodium lauryl sulphate. Microcapsules were prepared using cetrimide or 'double salt' as emulsifier and release of drug measured. Those prepared with 'double salt' released more slowly than those prepared with cetrimide.