Direct spectrophotometric determination of L-ascorbic acid in the presence of potassium cyanide.

A simple and highly sensitive direct spectrophotometric method was developed for the determination of L-ascorbic acid.Potassium cyanide (9.21x10 -5 mol dm -3 ) was used to stabilize ascorbic acid in aqueous medium.Th e molar absorptivity of the proposed method, which does not require an extraction procedure, was 1.38x10 4 dm 3 mol -1 cm -1 at 264 nm.Beer's law was obeyed in the concentration range of 0.26 -12.0 μg ascorbic acid cm -3 .Th e relative standard deviation was 1.40 % for the determination of 8.0 μg ascorbic acid cm -3 (n = 7).Th e substances commonly found in vitamin C products do not interfere with the determination of ascorbic acid.Other vitamins and organic acids interfere.Th e proposed procedure was successfully applied to the determination of ascorbic acid in pure form and vitamin C preparations.