The redox of ferrocen couple (Fc(+)/Fc) in the 1 M Cyphos IL-104/ethanol electrolyte system was studied via cyclic voltammetry under both inert and air atmospheres at room temperature. The anodic and cathodic peak potentials for Fc(+)/Fc were obtained at scan rates of 0.02, 0.1, and 0.2 V/s. The half-potential of Fc(+)/Fc versus a silver quasi-reference electrode (QAg) changed from 0.80969 to 0.84945 V and from 0.79872 to 0.8627 V at the glassy-carbon (GC)- and platinum (Pt)-working electrodes (WE), respectively, demonstrating that it depended on the presence of water from 0.1 to 0.3 wt.% in the 1 M Cyphos IL-104/ethanol electrolyte system. The half-potential of Fc(+)/Fc versus quasi-platinum (QPt) was not changed for both working electrodes and for the same solutions; the differences between the half-potentials of Fc(+)/Fc versus QPt were 0.0022 and 0.00416 V at the GC-and Pt-WEs, respectively. (C) 2015 Elsevier Ltd. All rights reserved.