Sensitive spectrophotometric method for determination of catecholamines in pure and pharmaceutical formulations

Abstract<br /> A sensitive and simple spectrophotometric method is developed for the determination of catecholamine drugs namely; methyldopa, dopamine and adrenaline in pure and pharmaceutical preparations. The method is based on the oxidation of the cited drugs with iron(III) in acidic medium and the liberated iron(II) reacts with 1,10-phenanthroline. The ferroin complex is colorimetrically measured at 510 nm against reagent blank. Beer's law was valid over the concentration ranges of 0.1-2.8, 0.1-2.0, and 0.2-6.0μg/ml and the molar absorptivities are 1.851×105, 1.544×105 and 4.331×104 l.mol-1cm-1 for methyldopa, dopamine and adrenaline respectively. The common excipients and additives did not interfere in their determinations. The proposed method was successfully applied to the assay of the above drugs in various dosage forms. <br /> Keyword: Spectrophotometry; Catecholamines; Ferric chloride;1,10-Phenanthroline.