Study on Catalytic Spectrophotometric Determination of Trace Iridium by Ir(Ⅳ)-Chlorophosphonazo-PA-KIO₄ System

A catalytic spectrophotometric method based on the catalytic effect of Ir(Ⅳ) on the oxidation of chlorophosphonazo-PA with KIO₄ in acidic medium has been proposed for the determination trace iridium. The optimal conditions were studied and the reaction was carried out directly in aqueous solution.The detection limit is 0.01 μg/10 mL. The Beer's law is obeyed in the range of 0.03～0.45 μg/10 mL. The method proposed has been applied to the determination of iridium in artificial sample with satisfactory results.