Conventional size electrodes and ultramicroelectrodes have been used to study heterogeneous kinetics of simple redox couples (TMPD/TMPD^.+ and TMN/TMN²⁺) as well as the electrochemical behaviour of compound related to foods, such as synthetic phenolic antioxidants in vegetable oils and lard and mycotoxins produced by fungus of the Alternaria alternata and Cercospora genus. The role of the reaction medium in determining the diffusional, thermodynamic and kinetic parameters is considered. Homogeneous chemical reactions coupled to the electrochemical discharge of TMPD and TMN are also studied by different methods. Electroanalytical techniques, mainly potential pulse voltammetry, have been found suitable for the analytical determination of antioxidants and mycotoxins.