Spectrophotometric Determination of L-Ascorbic Acid Based on Its Oxidation by Potassium Peroxodisulfate in the Presence of Cu(II) as Catalyst

A new, selective and accurate direct spectrophotometric procedure was developed for the determination of L-ascorbic acid (AA) in pharmaceuticals. Background correction was based on the oxidation of AA by potassium peroxodisulfate in the presence of Cu(II) as a catalyst. The molar absorptivity of the proposed procedure was 1.04 x 10(4) L/(mol cm) at 262 nm. Beer's law was obeyed in the concentration range of 0.68-16.00 mu g/mL for AA. The detection limit was 0.20 mu g/mL, and the relative standard deviation was 0.91% (n = 7) for 8.00 mu g/mL AA. Other compounds commonly found in pharmaceutical preparations did not interfere with the detection of AA. The proposed procedure was successfully applied to the determination of AA in pharmaceuticals, and the results obtained agreed with those obtained by iodine titration.