Institution: | National Health and Welfare Canada, Environmental Health Centre, Health Protection Branch, Ottawa, Canada Physical Metallurgy Research Laboratories, CANMET, Department of Energy, Mines and Resources, Ottawa, Canada |
Abstract: | Studies on the decomposition rates of the Mn(III) complex of cyclohexanediaminetetra-acetate (DCTA) in light and in darkness have shown that this complex is more stable than the one derived from ethylenediaminetetra-acetate. The optimum pH range for the determination of dissolved oxygen by means of the Mn(III)-DCTA complex is found to be between 3 and 4. The absorbance of this complex is independent of the amount of DCTA used (in the range 0.2–1.0 g) with water samples containing a maximum of 3.2 ppm of dissolved oxygen. Significant interferences are caused by the presence of CO2?3, HCO?3, S2O2?3, PO3?4, I?, NO?2, SO2?3, Ca2+, Fe2+ and Fe3+ at 500 times the oxygen concentration. |