Abstract: Cetyltrimethylammonium bromide(CTAB)and sodium dodecyl sulfate(SDS)were used as surfactants and effects of micelles on the basic hydrolysis of aspirin(ASP)were studied spectrophotometrically. When the concentrations of CTABare larger than 7.3?10^-3 mol/L, there is an inhibition of basic hydrolysis of ASP, the best concentration being 3.25?10^-3 mol/L. At a constant concentration of CTAB, the addition of a small amount of SDScauses the inhibition of CTABto decrease, indicating that SDStakes part together with CTABin the formation of mixed micelles.

Key words: surfactant, aspirin, basic hydrolysis, micelle, inhibition