A new oscillatory phenomenon based on Fe3+/Fe2+ was investigated systematically at the water/1,2-dichloroethane (W/DCE) interface by cyclic voltammetric technique. We focus our attention on study the concentrations of Fe3+/Fe2+ influence on oscillatory phenomena appearance in this paper. It was found that the current oscillation only occurred in the site of oxidation peak of Fe2+, and was related to the concentration of Fe3+ in the aqueous phase, indicating that the oscillation is caused by the specific adsorption of ion pairs at the liquid-liquid interface between Fe3+ in the aqueous phase and TPB- in the organic phase. Furthermore, DFT theory was used to calculate the mechanism of ion pair formation for the first time. The result suggested that TPB-Fe3+TPB- ion pair has the lowest-energy state, which provided qualitative support for ion pair embodied state. Combining experiment results and theoretical calculation, a specific adsorption of ion pair model on liquid/liquid interface was proposed and a mechanism for the observed current oscillation is also discussed in this paper. In addition, a spectrophotometric experiment was performed to evidence a strong attractive interaction between Fe3+ and TPB-. (C) 2012 Elsevier B.V. All rights reserved.