New insights on the electrochemical mechanism of epinephrine on glassy carbon electrode

• Epinephrine oxidizes in an EECEE mechanism instead of ECE. • The oxidations processes present potential inversions. • A more detailed EECEE mechanism to epinephrine oxidation is proposed. • The cyclization rate constants were experimentally obtained ( k f = 18.9 s −1 ) and validated by digital simulations. • The apparent Gibbs energies were obtained as a function of pH. The classic epinephrine’s ECE mechanism was revisited. The data obtained suggest that its mechanism is a multi-step irreversible electron transfer with a very fast intramolecular cyclization, an EECEE with a potential inversion, instead of a couple of two-electron processes in a single-step transfer. Moreover, the electrochemical and chemical steps are pH dependent. This conclusion is based on the combination of experimental data with Tafel analysis, digital simulations, and Gibbs energy and Randles-Sevcik predictions. A more detailed electrochemical mechanism was thus proposed to epinephrine’s electrooxidation.