The electrochemical properties of epinephrine, dopamine, and norepinephrine in aqueous solutions with various pH values have been investigated. The second redox couple of epinephrine shows an obvious reversible redox, with the formal potentials being pH dependent in the range 3 less than or equal to pH less than or equal to 13. The electrochemical properties of dopamine, epinephrine, and norepinephrine were pH dependent, and they exhibited different cyclic voltammograms. Cobalt(II) hexacyanoferrate films were electrocatalytically oxidation active for dopamine, epinephrine, and norepinephrine in aqueous solutions, with the electrocatalytic oxidation current developing through the Co(II)-CN-Fe(III) film. Cobalt(II) hexacyanoferrate also shows reversible electrocatalytic properties. Such films electrocatalytically reduce those oxidation products of dopamine, epinephrine, and norepinephrine that are produced from the electrocatalytic oxidation of these compounds by a cobalt(II) hexacyanoferrate film. Cobalt(II) hexacyanoferrate modified films are also electrocatalytically oxidation active for dopamine, epinephrine, and norepinephrine, and their electrochemical properties were investigated using the rotating ring-disk electrode method. (C) 2003 Elsevier Science B.V. All rights reserved.