The electrochemical behavior of copper in chloride solutions containing 0.001 M concentrations of small five- and six-ring member heterocyclic molecules was investigated by means of impedance spectroscopy. The investigation was performed by a new technique based on a broadband multisine excitation. This method allows for a quantification and separation of the measurement and stobastic nonlinear noises and for an estimation of the bias non-linear contribution. It as well reduces the perturbation brought to studied system by the measurement process itself. The measurement data for some experimental conditions was quantified by fitting into a equivalent circuit corresponding to a F. physical model both of them developed earlier. In general, the experimental results obtained show that the number of atoms in the heterocyclic ring and the molecular conformation have a significant influence on the electrochemical response of copper in the investigated environments. (c) 2005 Elsevier Ltd. All right reserved.