Analytical Sciences

Spectrophotometric Determination of Manganese by Using Redox Reaction of Tris(2,2′-bipyridine)osmium(II) with Mn⁷⁺

Ayman Ayoub ABDEL-SHAFI

Department of Chemistry, Faculty of Science, Ain Shams University, 11566 Abbassia, Cairo, Egypt

This paper reports on the analytical application of the oxidation reaction of [Os(bpy)₃]²⁺ by Mn⁷⁺ (MnO₄^-). The present study developed a very simple, sensitive and selective spectrophotometric method for the determination of manganese in an acidic medium. Three analytical wavelengths were employed in the UV and visible regions at 290, 315 and 480 nm. Beer's law was obeyed up to a concentration of 330 ng ml^-1 of Mn⁷⁺ at different wavelengths with regression equations 0.001 - 0.0042C_Mn, 0.001 + 0.0021C_Mn, and 0.001 - 9.34 × 10^-4C_Mn at 290, 315 and 480 nm, respectively. Under the optimum conditions, the achieved detection limits were 0.72, 1.37 and 3.32 ng ml^-1 at 290, 315, and 480 nm, respectively. In addition to the high sensitivity of the method (0.24 ng cm^-2 at 290 nm, 0.45 ng cm^-2 at 315 nm and 1.0 ng cm^-2 at 480 nm), it can be used for the determination of manganese in the presence of a large number of anions and cations, since it tolerates most of the potential interferents. The relative standard deviation was 0.5% (n = 11) for 90 ng ml^-1 manganese. The method was successfully applied to the determination of manganese in water from different resources.

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