The adsorption behaviour of a series of phosphatidylcholines (PCs) with saturated carbon chains of different length (DLPC, DPPC, DSPC, DAPC, and DBPC) at the electrified 1,2-dichloroethane/water interface was studied by measuring electrochemical impedance spectroscopy at the polarized interface. Two different trends in the interfacial capacitance were observed for any of the PCs the capacity dependence on the applied potential: strong adsorption occurs at negative potential with a marked decrease of C(E); increase of capacity is observed at positive potentials. It is demonstrated that the interfacial lipid adsorption was dependent on phospholipid concentration, applied potential, and phospholipid chain length. The potential and concentration dependence of the interfacial capacitance in the presence of these phospholipids were successfully described by a model based on the solution of the Poisson-Boltzmann equation in the interfacial region. (c) 2006 Elsevier B.V. All rights reserved.