The electrochemical decomposition of citric acid on gold and stainless steel AISI 304 (18% Cr, 10% Ni) electrodes was investigated using the technique of in situ InfraRed Reflection Absorption FTIR Spectroscopy (IRRAS) in combination with cyclic voltammetric measurements. The applied potential sweep starts from -0.265 up to +2.5 V on gold and from +0.4 up to +2.4 V on steel electrodes. The initial potentials of the anodic decomposition of citric acid could be observed on both electrode materials. Carbon dioxide was detected as decomposition product. Using stainless steel electrodes, the decarboxylation of citric acid and the forming of citrate complexes were observed. The consumption of citric acid is both due to its anodic decomposition and the generation of soluble citrate complexes of iron, nickel and chromium, resulting from the transpassive dissolution of the electrode material. At potentials more positive than +500 mV both processes are occurring simultaneously. (c) 2006 Elsevier Ltd. All rights reserved.