Optimisation procedure for the inhibitive determination of chromium(III) using an amperometric tyrosinase biosensor

An enzymatic amperometric procedure for measurement of chromium(III), based on the inhibitive action of this metal on tyrosinase enzyme activity, was developed for this purpose. A glassy carbon electrode was used as a support for the electropolymerisation of a polypyrrole (PPy) film, in which tyrosinase was immobilised. The parameters were optimised using experimental design methodology. To determine the optimum conditions and the influence of the factors in the experiment, a canonical analysis of the response surface was carried out. Under these conditions, the repeatability (R.S.D. < 5.8%), the reproducibility (R.S.D. < 8.3%), and the stability of the modified electrode were all analysed. The detection limit for Cr(III) was calculated at a value of 5.0 × 10^-7 mol dm^-3 with a relative standard deviation (R.S.D.) of 5.8%. Analysis of the possible effect of the presence of foreign ions in the solution was performed. The method was applied to determine levels of chromium(III) in spiked urine samples, in the waste water from a tannery, and in river water from an industrial area.