A colorimetric method for ascorbic acid assay of pharmaceuticals

A rapid photometric procedure for the determination of ascorbic acid is described. It involves the reduction of iron(III) to iron(II) with ascorbic acid and the formation of a pink colored complex by the reaction of reduced iron(II) with picolinic acid, followed by the extraction of the complex into trioctylamine solution in chloroform and measuring the absorbance at 470 nm. The procedure has been applied to the assay of pharmaceutical preparations containing vitamin C.