Spectrophotometric Determination of Ascorbic acid in Pharmaceutical Products with the Copper(II)-rhodanine Reagent

Publisher Website
Google Scholar
Abstract
A simple method has been developed for the determination of ascorbic acid(AA) in pharmaceutical products by the copper(II)-5-(4-hydroxy-3-methoxybenzilidene) rhodanine reagent. The method is based on the oxidation of AA with the reagent and complexation of copper(I) produot with unchanged rhodanlne. The red complex soluble In dioxane-water yields an effective molar absorptivity of 2.6x104 l.mol−1. cm-1 at 473 nm for AA at an apparent pH of 3.8.Beer's law is obeyed between 6.25x10−6and 3.75x10−5 mol.dm−3 concentrations of AA with a relative standard deviation of 3.4%.The method has been successfully applied to vitamin C assay in pharmaceutical formulations. Biologically important thiols such as cysteine and glutathione could also be quantified by the same procedure with a molar absorptivity of 1.3x104 l.mol−1 cm−1.