Study on spectrophotometric determination of trace manganese by tribromochlorophosphonazo-MnII-KIO_4 catalytic system

A new catalytic spectrophotometric method for the determination of trace amounts of manganese has been developed.The method was based on oxidation of tribromochlorophosphonazo by potassium periodate in HAc-NaAc medium and in the presence of aminotriacetic acid as activator.The optimum reaction conditions and reaction mechanism were studied.The apparent activation energy and apparent reaction rate were found as Ea′=37.73 kJ/mol and k′=8.85×10-4s-1,respectively.The detection limit of the method was 2.3×10-9 g/mL.The linear ranges for the determiantion of manganese were 0-10.0 ng/mL.The recoveries of 95.2%-103.5% and the relative standard deviation of 2.1%3.9%(n=6)were obtained for the determination of trace manganese in environmental water samples.