Study of the Histamine Electrochemical Oxidation Catalyzed by Nickel Sulfate

Thin layer technique was applied to the indirect anodic oxidation of histamine, catalyzed by NiSO 4 . Coulometric determination of the electron number demonstrates that histamine complexes Ni (II) and resulting adducts can be electrochemically oxidized in a single‐electron reaction, to lead Ni (III) ‐histamine. The system Ni (III) /Ni (II) acts as ‘redox mediator’ for histamine oxidation. The equilibrium constant of the Ni (II) ‐histamine complex formation was 10 6 , value showing the strong affinity between species. High content of histamine (>0.1 M), detected in fresh fish (previously exposed to the sun) extracts, showing potentialities for future design of a sensor for direct measurement in fish.