Study of the Histamine Electrochemical Oxidation Catalyzed by Nickel Sulfate

Thin layer technique was applied to the indirect anodic oxidation of histamine, catalyzed by NiSO4. 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 106 , 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.