Kinetic determination of iodide traces based on the manganese(III) metaphosphate-arsenic(III) reaction in the presence of orthophosphoric acid
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The kinetics of the iodide-catalyzed Mn(III) metaphosphate-As(III) reaction was studied in the presence of orthophosphoric acid. The reaction rate was followed spectrophotometrically at 516 nm. It was established that orthophosphoric acid increased the reaction rate and that the extent of the non-catalytic reaction was extremely small. A kinetic equation was postulated and the apparent rate constant calculated. The dependence of the reaction rate on temperature was investigated and the energy of activation and other kinetic parameters determined. Iodide was determined under the optimal experimental conditions in the range 0.6-2.5 ng.mL(-1) with a relative standard deviation of up to 6.7% and a detection limit of 0.12 ng mL(-1). The effect of foreign ions on the accuracy of the determinations was also investigated.
Keywords:manganese(III) metaphosphate-arsenic(III) reaction / orthophosphoric acid / kinetics / iodide / kinetic determination
Source:MICROCHIMICA ACTA, 2004, 144, 1-3, 51-56
- Springer-Verlag Wien, Vienna