Therefore, we propose a different mechanism for the studied process. In the initial electrochemical step (1) oxidation of tyrosine and Cu(II) ions occur at very similar potentials, especially at lower pH values. However, as the pH increases, tyrosine oxidation occurs at slightly lower potentials compared to Cu(II). Therefore, an obvious widening of the half peak width is seen. Considering this, it might be reasonable to divide the reaction in Eq. 1 into separate steps. While the second step is the same as in EC mechanism. An alternative model is therefore an electrochemicalelectrochemical chemical (EEC) mechanism such as the one in eq 5: