We present the availability of a fluorous solvent, 1,1,1,2,3,4,4,5,5,5-decafluoropentane (C5F10), for the non-aqueous medium in liquid-liquid electrochemistry. The solvent is immiscible, and forms stable interface with water (W). The solvent dissolved a high concentration of a hydrophobic electrolyte, tetrabutylammonium bis(nona fluorobutanesulfonyl)imide (TBABNSI), and theTBABNSI (C5F10) solution gave a high conductivity. The TBABNSI (C5F10)vertical bar LiCI (W) interface gave a polarizable potential window. Within the potential window, tetramethylammonium ion gave a reversible voltammetric wave due to its transfer across the C5F10 vertical bar W interface. The potential window became wider by replacement of the supporting electrolytes in C5F10- and W-phases. The results indicate that various ion-transfer reactions at the C5F10 vertical bar W interface can be studied voltammetrically. (C) 2017 Elsevier B.V. All rights reserved.