Kinetic-spectrophotometric determination of manganese(II) at the nanogram level based on its catalytic effect on the oxidation of an azo dye with hydrogen peroxide

Abstract

A catalytic method for the determination of trace amounts of manganese(II) based on its catalytic effect on the oxidation of 3-(2-hydroxyphenylazo)pyridine-2,6-diol is proposed. The synthesis of this dye is described and the reaction is monitored spectrophotometrically by measuring the absorbance of the dye at 472 nm. The kinetic parameters of the reaction have been determined. The calibration graph [tan αvs. manganese(II) concentration] is linear in the range 0.5–9.1 ng ml^–1 of manganese(II), the relative standard deviation being 3.7% for 2.23 ng ml^–1. The method has few interferences and has been applied to the determination of manganese(II) in foodstuffs.