Electron transfer reactions between iron(II/III)-complexes are of general interest for corrosion processes, biological processes and technical applications. The cathodic reduction of Fe-III-triethanolamine (TEA) complex to form the Fe(II)TEA-form of the complex has been examined by cyclic voltammetry. In the presence of Fe-III-(D)-heptagluconate (HDGL), complex catalytic currents are observed due to homogenous chemical reaction between Fe(II)TEA and Fe-III(HDGL)(2) which regenerates Fe(III)TEA. This method can be used to determine the rate constant of the redox reaction between Fe(II)TEA and Fe-III(HDGL)(2) with k'(f) = 88 ± 12dm(3) mol(-1) s-(1). © 2005 Elsevier B.V. All rights reserved.