Determination of Manganese in Natural Media by Anodic Stripping Voltammetry Using a Rotating Solid Silver Amalgam Electrode

Detection of Mn(II) using differential pulse anodic stripping voltammetry (DPASV) on solid silver amalgam electrode is introduced. A well-defined peak for the oxidation of Mn(0) to Mn(II) was observed around -1.45 V in NH4Cl (0.05 M) solution. Concentrations down to 1 mu g/L were measured in NH4Cl (0.05 M) with 900 s deposition time at -1.70 V, and good linearity was observed (r(avg)(2) = 0.993) for standard additions in different concentration ranges (1-3 mu g/L, 10 mu g/L-60 mu g/L, and 50 mu g/L-250 mu g/L). For all measurements relative standard deviation was within 5% (n = 9). Interactions between Mn and Cd, Ni, Cu, Pb and Zn were examined, and it was found that lead and nickel significantly interfere, while zinc, cadmium, copper, and mercury did not interfere within reasonable concentration ranges. The method was demonstrated for online detection of manganese in a contaminated river where the Mn(II) concentration varied between 3 and 15 mu g/L. The relation between the Mn(II) concentration in the river water and the vessel traffic was observed due to the presence of high concentrations of Mn(II) in anoxic pore waters.