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In this paper, a novel current oscillatory phenomenon for Cu2+ at the water/1,2-dichloroethane interface is reported with cyclic voltammetry and potential-step chronoamperometry. The small irregular current spikes were only observed near the site of the oxidation peak of CuCl2− and were mainly related to the Cu2+concentration in the aqueous phase. Our experimental results demonstrated that the current oscillation is caused by specific adsorption of ion pairs at the W/DCE interface between Cu2+ in the aqueous phase and TPB− in the organic phase. Therefore, a specific adsorption of ion pair model has been formulated for the current oscillation at the liquid/liquid interface. The DFT calculation method was used to explain the mechanism of ion pair formation. The calculation results suggested that the TPB−Cu2+TPB− ion pair has the lowest-energy state, thus providing qualitative support for the ion pair model. A probable mechanism for the observed current oscillation was also discussed in this paper. At the same time, a spectrophotometric experiment was performed to evidence a strong attractive interaction between Cu2+ and TPB−. [ABSTRACT FROM AUTHOR]