Microencapsulation of ascorbic acid by coacervation and solvent evaporation techniques

Abstract

Ascorbic acid ethylcellulose-walled microcapsules were prepared by temperature induced coacervation and solvent evaporation techniques. Effects of core of wall ratios, types and amounts of plasticizers (i.e., triacetin, triethyl citrate, and dibutyl sebacate) on the properties of microcapsules prepared by coacervation technique and effects of ethylcellulose concentrations, core to wall ratios, types and amounts of surfactants (i.e., Span80 and Tween80) on the properties of microcapsules prepared by solvent evaporation technique were investigated. The temperature induced coacervation technique gave high yields (95%) and drug entrapments (100-104%) of irregular-shaped, aggregate microcapsules. The higher the core to wall ratio, the smaller the mean size and the greater the drug release rate. Thirty percent dibutyl sebacate was suitable for use as a plasticizer for slow released ethylcellulose-walled microcapsules. When the microcapsules were prepared by the solvent evaporation technique, the yields and drug entrapments ranged from 66-88% and 55-93%, respectively. Six percent ethylcellulose provided slow released and high yield microcapsules. The higher the core to wall ratio, the greater the mean size and the drug release rate. The higher concentration of Span80 increased drug release rate associated with presence of drug crystals on the microcapsule surface. The microcapsules prepared using 1.5% Tween80 showed the slowest release rate due to the less porous internal structure. The stability study indicated that ascorbic acid in the microcapsules with 1.5% Tween80 degraded the fastest.