The electrochemical behaviour of phenol, catechol, hydroquinone, resorcinol, dopamine, and para-substituted phenolic compounds, 4-ethylphenol, tyrosine, and tyramine, was studied over a wide pH range using a glassy carbon electrode. The oxidation of phenol is pH dependent and irreversible, occurring in one step, and followed by hydrolyse in ortho- and para-positions, leading to two oxidation products, catechol and hydroquinone. The oxidation of phenol oxidation products, ortha-phenol and para-phenol, is reversible and pH dependent. The oxidation potential of para-substituted phenols varies slightly due to their substituent group in position C4, and occurs in one oxidation step corresponding to the oxidation of phenol. The oxidation products of this group of para-substituted phenols are reversibly oxidised and adsorb on the electrode surface. (C) 2011 Elsevier B.V. All rights reserved.