Kinetic determination of trace manganese(II) using its catalytic effect on the oxidation of 2,3-dihydroxynaphthalene

A catalytic method for the simple, sensitive and selective determination of manganese(II) was developed. This method is based on the catalytic oxidation of DHN with hydrogen peroxide in the presence of ethylenediamine at pH 10.5. The decrease of the absorbance at 330 nm, owing to the manganese(II)-catalyzed oxidation of DHN, was monitored. In this reaction, ethylenediamine acted both as an activator and a masking agent. Manganese(II) could be determined in the concentration range of 20 to 1600 pg cm(-3) (PPt). The present method was successfully applied to the determination of trace manganese(II) in tap water without preconcentration of Mn(II), and without removing other coexisting ions.