A micromanipulator combined with a microinjection system was employed to inject micro-droplets of aqueous solutions containing redox-active species on selected areas of graphene. Chronoamperometric and voltammetric measurements were performed in order to investigate the diffusion regime established within the micro-droplets. The heterogeneous electron transfer rate for two model redox couples, Fe(CN)(6)(3-) and IrCl62- were estimated on various regions of chemical vapour deposited monolayer and turbostratic Mayer graphene on the basis of the voltammetric responses. New insights are thus obtained into the electron transfer properties of graphene, which is of primary importance for its exploitation as an electrode material. (C) 2013 The Authors, Published by Elsevier Ltd. All rights reserved.