Colorimetric determination of ascorbic acid in pharmaceutical preparations and biological samples

A simple and rapid method is described for the determination of L-ascorbic acid, based on its reduction of iron (III). The iron(II) thus formed is complexed with quinaldic acid and pyridine. The absorbance is measured at 380 nm after extracting the complex into chloroform. Beer's law is obeyed over the concentration range 2.5–25 μg ml−1 ascorbic acid. The results obtained are accurate and reproducible with the standard deviation of 0.0076. The method has been applied to the analysis of pharmaceuticals and biological samples with satisfactory results.