Analytical-kinetical study on the quinalizarin-hydrogen peroxide indicator reaction for Co2+ determination

By a kinetic study of the indicator reaction of quinalizarin with hydrogen peroxide, catalysed by Co2+ ions, the optimum conditions necessary for determining traces of the catalyst have been found. These conditions are: pH=12.0 (sodium tetraborate-sodium hydroxide buffer), wavelength of measurement 565 nm,c (H2O2)/c(R)=200, temperature=25° C, Co2+ concentration range 1×10−8-2×10−7M. A mechanism similar to that for enzymatic reactions, involving the occurrence of two intermediate complexes, gives a good explanation for the optimal conditions found.