Highly sensitive and selective determination of manganese in tea leaves by a catalytic kinetic spectrophotometric method

The catalytic effect of manganese(II) on the oxidation of barium diphenylamine sulfonate (BDAS) with potassium bromate in sulfuric acid was studied. Progress of the reaction was monitored, spectrophotometrically, by measuring absorbance changes at 547.5 nm. A highly sensitive, selective and simple method was accordingly developed for the determination of trace amounts of Mn(II), with no need for a separation or pre-concentration step. Effects of reaction time, concentration of reagents, temperature and ionic strength on the reaction rate were studied. In the optimized conditions, manganese could be determined in a range of I to 60 ng mL(-1) with a detection limit of 0.2 ng mL(-1). The proposed method was successfully applied to the determination of manganese in tea leaves.