Spectrophotometric determination of ascorbic acid using an iron(II)-pyridine-picolinic acid complex

An extractive spectrophotometric method for the determination of micro amounts of ascorbic acid has been developed by exploiting its reducing nature. Iron(III) is converted to iron(II) by the addition of ascorbic acid, which forms an extractable yellow-colored complex with picolinic acid and pyridine. The absorbance is measured at 400 nm. Beer's law is obeyed in the concentration range 0.4-5.6 mu g ml(-1). This method has been satisfactorily applied to the analysis of a variety of samples, including pharmaceuticals, food products and biological fluids.