STUDIES ON STABILITY OF POLYOXYETHYLENE CASTOR OIL EL-40 AND TWEEN 80 IN CALCIFEROL SOLUBILIZED SYSTEMS

The kinetics of hydrolysis of polyoxyethylene castor oil EL-40 and Tween 80 in calciferol solubilized systems at 55℃. were studied. Each of these surfactants was degradated by a pseudo-first order reaction. The hydrolysis appeared to be catalysed by specific acid-base and pH of maximum stability for each in calciferol solubilized systems was 6 at 55℃. Polyoxyethylene castor oil EL-40 was more stable than Tween 80.In the experimental conditions, it was also found that ionic strength, initial concentration, general acid-base catalysis had no effect on the degradation of both surfactants. Among the solubilizates, calciferol could decrease the degradation of these surfactants, probably due to the difference in locations within micelle but cetyl alcohol and p-hydroxybenzoic acid showed no effect at pH 2. 2.