Determination of manganese (II) in some medicinal plants and their decoctions by a kinetic spectrophotometric method

The catalytic effect of manganese (II) on the oxidation of the azo dye tropaeolin 00 with potassium periodate in the presence of 1,10-phenanthroline was investigated. The reaction was followed spectrophotometrically by measuring the decrease in the absorbance of the azo dye at 445 nm. Under the optimum analytical conditions, manganese (II) in the range 0.05-2.5 ng/mL could be determined by the fixed-time method with a detection limit of 0.02 ng/mL. The developed method is highly sensitive, selective and simple, and was applied successfully to analyse decoctions of some medicinal plants for trace amounts of total manganese (II) and free manganese (II) ions without separation.