The effect of core-to-wall ratio and Span 80 concentration on the properties of ascorbic acid microcapsules

Ethylcellulose microcapsules containing ascorbic acid were prepared by the emulsification-solvent evaporation technique. The effect of core-to-wall ratios and surfactant concentrations on the dissolution rate and size distribution of the ascorbic acid microcapsules were studied. Span 80 was used as a dispersing agent and light liquid paraffin as a continuous phase. The dissolution of ascorbic acid microcapsules was studied using the USP rotating basket method. A high core-to-wall ratio resulted in an increase of both microcapsule size and drug release rate. For a given core-to-wall ratio a high concentration of Span 80 increased the drug release rate, this was associated with the presence of drug crystals on the microcapsule surface.