Determination of L-Ascorbic Acid in Pharmaceuticals by Using Chlorpromazine Hydrochloride as Oxidation-Reduction Indicator

A simple method for determination of L-ascorbic acid of (1‐50) μg/ml in pure form and pharmaceuticals is described. The rapid procedure is based on the direct visual titration of L-ascorbic acid with ceric ammonium sulphate in the presence of chlorpromazine hydrochloride in a mixture of sulphuric and phosphoric acids as a redox indicator. The relative standard deviation of the method is ±(0.0111706−0.12539). An interference study is carried out for the different acids. Most importantly, the new method is applied for a variety of vitamin c in pharmaceuticals and successful results are achieved. Chlorpromazine hydrochloride is used as a redox indicator in oxidised form (Sulfoxide form) in acid mixture with maximum absorbance at 530 nm, formal redox potential was determined to be 285 mv. All the titrations were followed potentiometrically for comparison.