SIMULTANEOUS DETERMINATION OF CHROMIUM(VI) AND TUNGSTEN(VI) BASED ON THEIR CATALYTIC EFFECT ON THE REACTION BETWEEN HYDROGEN-PEROXIDE AND IODIDE

Two catalysts, which catalyse a common indicator reaction, cad be dete rmined simultaneously through a single catalytic kinetic run, if one o f the catalysts is losing its catalytic activity because of an inhibit ion reaction. Using this principle, Cr-VI and W-VI can be determined s imultaneously 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-V I 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.