Direct Spectrophotometric Determination of L-Ascorbic acid in Pharmaceutical Preparations using Sodium Oxalate as a Stabilizer
A simple and highly sensitive direct spectrophotometric method was developed for the determination of L-ascorbic acid. Sodium oxalate (0,0056 mol/dm) was used to stabilize L-ascorbic acid in aqueous medium. The molar absorptivity of the proposed method, which does not require an extraction procedure, was 1.42x10 dm mol cm at 266 nm. Beer’s law was obeyed in the concentration range of 0.857 – 12.0 μg ascorbic acid/cm. The relative standard deviation was 0.81 % for the determination of 8.0 μg ascorbic acid/cm (n = 7). The substances commonly found in vitamin C products do not interfere with the determination of ascorbic acid. Other vitamins, Ca(II) and benzoate interfere. The proposed procedure was successfully applied to the determination of ascorbic acid in pure form and vitamin C preparations. Index Term-Spectrophotometry, L-ascorbic acid, sodium oxalate, stabilizer.