Potentiometric coulometry based on charge accumulation with a peroxidase/osmium polymer-immobilized electrode for sensitive determination of hydrogen peroxide.

Abstract: The charge accumulation due to peroxidase (POD)-catalyzed reduction of H2O2 in a test solution (4μL) by Os(II) in a POD/PVI[Os(dmebpy)2Cl]-immobilized layer on an electrode (PVI=poly(1-vinylimidazole), dmebpy=4,4′-dimethyl-2,2′-bipyridine) was monitored potentiometrically for the detection of H2O2. Before potentiometry, the Os(II)/Os(III) ratio of the modified electrode was controlled by pre-electrolysis at a given potential in a separated electrolysis cell. The redox potential of the Os polymer film in the test solution shifted to the positive side on the addition of H2O2 and reached a constant value due to the accumulation of Os(III) in the film. The total amount of the accumulated charge was determined from the area of the portion corresponding to the redox potential shift on a reversible cyclic voltammogram recorded separately. The low detection limit (5pmol H2O2) was realized with 82–90% of the recovery percentage. [Copyright &y& Elsevier]