A New Kinetic-Spectrophotometric Determination of Manganese (II) in Natural Water Samples by Redox Reaction

A simple and sensitive first order kinetic-spectrophotometric method is proposed for the determination of Manganese (II) in nanogram amounts. This method is based on the catalytic effect of Manganese (II) on the oxidation of O-Anisidine by potassium bromate in acidic medium. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of O-Anisidine solution at 420 nm by fixed time method. The proposed method allows determination of Manganese in the range of 0.128–7.213 mol.dm-3 with good precision and accuracy. The optimization of the operating conditions regarding concentrations of the reagents; temperature and interferences are also investigated. The reaction was found to be first order in O-Anisidine, Manganese (II) and bromate. The rate of the reaction is found to have an inverse dependence on hydrogen ion concentration. The results obtained were in excellent agreement with the standard methods such as atomic absorption spectrometry. The coefficient of variance and % error were in the range of 1.87–3.26, 0.78–1.57% respectively. The method showed fairly good selectivity and sensitivity, low cost, cheapness, low detection limit and rapidity. The determination of Manganese (II) can easily and successfully be applied to the natural water samples.