Abstract

The present investigation is a preformulation study on stabilization of vitamin C with disodium edetate and some antioxidants. The concentration of disodium edetate for the stabilization of vitamin C in aqueous solution at pH 4.0 was found to be critical: less than 0.05% w/v was insufficient and more than 0.05% w/v was detrimental. The first order kinetics was the prevailing mechanism in this case and kinetic rate constants were calculated by regression analysis. Differential scanning calorimetric study suggested the effect of disodium edetate concentration on the thermal behavior of vitamin C and results are reciprocative of kinetic study. The study was further extended to understand the effect of some antioxidants such as cysteine, thiourea and nicotinic acid on the stabilization of vitamin C. In all the cases the effect of stabilization increased with increased concentration. Cysteine was found to be more protective to the aqueous stability of vitamin C. In total both disodium edetate and antioxidants were found to improve the stability of vitamin C. However, required stability was not achieved with permissible concentration of both the stabilizers suggesting the need of further investigation.