Voltammetric behaviour of ferrocene in olive oils mixed with a phosphonium-based ionic liquid

•Voltammetry is performed in olive oils mixed with a phosphonium-based ionic liquid.•Measurements are made in the oil/RTIL mixtures using ferrocene as probe molecule.•Platinum disk microelectrodes are employed for cyclic voltammetric measurements.•Under these experimental conditions, mixed radial-planar diffusion regimes occur.•Diffusion coefficient values for Fc and Fc+ reflect the viscosity of oil and RTIL media.