Interfacial tension and impedance measurements were used to study the electrochemical properties of the interface between 0.1 M LiCl in water and 0.05 M tetrabutylammonium tetraphenylborate in nitrobenzene in the absence and the presence of various tetraalkylammonium ions. While the presence of these ions has no effect on the interfacial tension, the interfacial capacity can be considerably enhanced. This enhancement appears to be an artefact arising from the inadequate representation of the interface or the electrochemical cell by the Randles equivalent circuit employed for impedance data analysis. Modifications to this equivalent circuit are discussed.