In a hydrophilic droplet three-electrode system, electroactive species within the droplet play very important roles in the electron-transfer (ET) process on the solid/electrolyte interface, which can then induce an ion-transfer (IT) reaction at the liquid/liquid interface. In this work, several redox couples and electroactive species are chosen to study ET-IT coupling processes at the water/1,2-dichloroethane (W/DCE) interface by cyclic voltammetry (CV) and Osteryoung square wave voltammetry (OSWV). Among them, the redox couple Ru(NH3)6(3+/2+) has been found to have the widest useful potential window of about 1.2 V. A hydrophilic droplet three-electrode system using a single electroactive molecule instead of a redox couple has been confirmed to be stable and has similar functionality to a redox couple. In addition, the lipophilicity of antiplatelet drug clopidogrel at the W/DCE interface is investigated and its ionic partition diagram has been constructed. Protonated clopidogrel is detected in a linear concentration range of 5.0-50 μM and the limit of detection (LOD) is calculated to be 3.0 μM by using the hydrophilic droplet system Ru(NH3)6(3+/2+) and OSWV.