Fluctuation analysis and faradaic impedance measurements were used to study tetraethylammonium ion transfer across the water/nitrobenzene micro-interface at equilibrium potential. Lithium chloride and tetrabutylammonium tetraphenylborate were used as supporting electrolytes in a symmetrical electrochemical cell with zero cell potential difference. A remarkable difference in the data obtained by these two techniques in the low frequency range (< 50 Hz) indicates the presence of another process connected with the charge transfer reaction. This process was not detected by conventional electrochemical methods using any type of perturbation signal. An attempt is made to attribute this effect to local conventions at the interface.