Study of the system manganese(VII)-3,7-bis(dimethylamino)-phenothiazin-5-ium chloride-water-1,2-dichloroethane Using UV-spectrophotometry

The system manganese(VII)-3,7-bis(dimethylamino)-phenothiazin-5-ium chloride (MB)-water-1,2-dichloroethane has been studied using UV-spectrophotometry. The molar absorptivity of the complex is (3.86 ± 0.06) × 104 L mol−1 cm−1 at 290 nm and the system obeys Beer’s law in the range 0.1–0.99 μg mL−1 Mn(VII). The detection limit (DL) and quantitation limit (QL) of Mn(VII) determination were found to be 0.0146 and 0.049 μg mL−1, respectively. The composition of the complex is established as MB: MnO4− = 1: 1. Extraction investigations of the system discussed were carried out. The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase was determined: extraction constant Kex = (1.12 ± 0.05) × 105, distribution constant KD = 75.61 ± 0.1 and association constant β = (1.48 ± 0.08) × 103. A new method has been developed for the microdetermination of manganese(VII) in plants and steels.