Determination of L-Ascorbic Acid in Pharmaceutical Preparations Using Direct Ultraviolet Spectrophotometry

A new, selective and accurate direct ultraviolet spectrophotometric method was developed for the determination of L-ascorbic acid in pharmaceuticals.Th e oxidation of L-ascorbic acid by iodate in an acidic medium was used as a means of correcting for background absorption.Th e molar absorptivity of the proposed method was found to be 8.71x10 3 dm 3 mol -1 cm -1 at 250 nm.Beer's law was obeyed in the concentration range of 0.46 -16.00 μg cm -3 for L-ascorbic acid.Th e relative standard deviation was 0.67 % for a concentration of 8.00 μg cm -3 of ascorbic acid (n = 7).Th e ingredients commonly found in vitamin C and multivitamin products did not interfere.Th e proposed procedure was successfully applied to assays of L-ascorbic acid in pharmaceutical preparations.Th e results obtained with the proposed method showed good agreement with those given by the titrimetric method using iodine.