Simultaneous determination of chromium(VI) and tungsten(VI) based on their catalytic effect on the reaction between hydrogen peroxide and iodide

Abstract

Two catalysts, which catalyse a common indicator reaction, can be determined simultaneously through a single catalytic kinetic run, if one of the catalysts is losing its catalytic activity because of an inhibition reaction. Using this principle, Cr^VI and W^VI can be determined simultaneously based on their catalytic effect on the reaction between H₂O₂ and I^–. Mixtures of Cr^VI in the range 0.015–0.3 mg l^–1 and W^VI in the range 0.005–0.1 ng l^–1 were determined. The reason for the loss of the catalytic activity of Cr^VI was investigated in detail.