Spectrophotometric Determination of Certain Vicinal Dihydroxybenzene Derivatives with Sodium Bismuthate

Abstract

A simple and accurate spectrophotometric method is developed for the determination of certain vicinal dihydroxybenzene derivatives, namely, dopamine (DPH), levodopa (LD), methyldopa (MD) and pyrocatechol (PC) using sodium bismuthate in an acid medium. The method is based on the formation of a yellow colored product by the oxidation of vicinal dihydroxybenzene derivatives using sodium bismuthate. Beer's law was obeyed over the concentration range of 8–130 μg/mL with the maximum absorption at 422–429 nm. The molar absorptivity and Sandell's sensitivity as evaluated from Beer's law data were found to be in the range of 1.02–1.34 × 10–3L mol–1cm–2and 108–185 ng/cm2respectively. The proposed method has been successfully applied for the determination of DPH, LD and MD in injections and tablets of pharmaceutical preparations. The reliability of the methods was established by replicate determinations with the reported and official method.