A zucchini-peroxidase biosensor applied to dopamine determination

A biosensor modified with peroxidase from crude extract of zucchini (Cucurbita pepo) was developed for the determination of dopamine in pharmaceutical samples. This enzyme catalyses the oxidation of dopamine to dopaminequinone, in presence of hydrogen peroxide, which the electrochemical reduction can be followed at a peak potential of -0.02 V. The recovery of dopamine from the samples ranged from 94.8% to 106% and a rectilinear analytical curve for dopamine concentration from 5.0 × 10-4 to 3.0 × 10-3 mol L-1 (r = 0.9982) was obtained. The detection limit was 2.6 × 10-5 mol L-1 and the relative standard deviation was less than 1.2% for 7.9 × 10-4 mol L-1 dopamine in 0.1 mol L-1 phosphate buffer solution at pH 6.0 (n = 10).