Fluorometric determination of hydrogen peroxide in milk by using a Fenton reaction system

A simple and highly sensitive fluorometric method is proposed for the determination of H2O2 in milk samples. In this method, non-fluorescent coumarin is oxidised to highly fluorescent 7-hydroxycoumarin by hydroxyl radicals (OH) generated in a Fenton reaction, and the oxidation product has strong fluorescence with a maximum intensity at 456 nm and can be used as a fluorescence probe for H2O2. Under the optimal conditions (2.5 × 10−4 mol L−1 iron(II) ions, 4.0 × 10−4 mol L−1 coumarin, solution pH 3.0, reaction time 9 min, and excitation at 346 nm), the proposed method presents wide linear responses between the fluorescence intensity and H2O2 concentration in a wide range from 2.0 × 10−8 to 2.0 × 10−5 mol L−1, with a detection limit (S/N = 3) of 5.0 × 10−9 mol L−1. After possible interferences are evaluated for a series of chemical substances, the present method has been applied to the determination of hydrogen peroxide in milk with satisfactory results.