Abstract: A new electrochemical method for determining dissolved oxygen concentration is developed. It employs cobalt based oxide or complex to modify a conductive electrode surface. This method can be applied to determine dissolved oxygen in regard to medical and environmental demands. The chemical formula of the cobalt based oxide or complexes can be shown as CoxOy or CoaLb. Both “x” and “a” represent the number of cobalt atom; while “y” and “b” represent the number of oxygen atom and the number of coordinating ligand, respectively. For instance, the best known example of cobalt oxide is CO3O4, and the best known examples of cobalt complexes are cobalt phthalocyanine (CoPC) and cyanocobalamin (vitamin B12), or other macrocyclic complexes with a metallic nucleus of cobalt. The present invention determines the concentration of dissolved oxygen in solution in potentiostatic mode with three electrodes. As a result, the dissolved oxygen can be determined between 0.0V and ?0.3V vs.

Abstract: A new electrochemical sensor for determining hydrogen peroxide concentration having a mixed-valence metal oxide of MxOy deposited on an electrode surface thereof is disclosed, wherein M is a transition metal and has two or more than two valences. MxOy, for example, is M3O4 where M is Mn, Fe, Co or Pb, Tb4O7 or Pr6O11. Further, this invention also discloses an electrochemical sensor for determining a concentration of a hydrogen peroxide precursor, wherein a catalyst is immobilized in the matrix or on the surface of the mixed-valence metal oxide on the electrode. In a typical biochemical system, the catalyst can be a glucose oxidase and blood glucose is catalyzed to form hydrogen peroxide, so that the concentration of blood glucose is determined.