KINETICS OF ASPRIN HYDROLYSIS IN AQUEOUS SOLUTIONS OF SURFACTANTS. III: SODIUM LAURYL SULFATE

Document Type : Original Article

Authors

1 Department of Pharmaceutics, Faculty of Pharmacy, Assiut University, Assiut, Egypt

2 Department of Pharmaceutics, Faculty of Pharmacy, University of Connecticut , Storrs, CT. 06268, USA

Abstract

The hydrolysis of aspirin solution at a variety of pH values  and in presence of increasing concentrations of sodium lauryl sulfate (SLS) was investigated at 35°C. The hydrolysis followed first order kinetics. The results indicate that the presence of sodium lauryl sulfate results in a protection of aspirin against hydrolysis and the degree of protection was found to be dependent on the surfactant concentration. This finding was explained on the basis that as the surfactant concentration was increased, aspirin was distributed in a favour of the micellar phase and the amount of aspirin exists in the true aqueous phase, which is susceptible to hydrolysis, is reduced. Also, the data revealed that the presence of sodium layryl sulfate did not alter the optimum pH value for the stability of aspirin solution which was found to be 2.4.