Experimental cyclic voltammetry at a hemispherical mercury microelectrode in acetonitrile solution containing 3 mM cobaltocenium hexafluorophosphate and different concentrations of supporting electrolyte is compared with theoretical simulations using the Nernst-Planck-Poisson system of equations without the assumption of electroneutrality and is found in to be in good agreement Deviations from diffusion-only theory are analyzed in terms of migration and potential drop in the solution as a function of the concentration of supporting electrolyte We are unaware of previous reports in which non-steady-state cyclic voltammetry without supporting electrolyte has been quantitatively and fully simulated so this work opens up a new area for voltammetry (C) 2010 Elsevier B V All rights reserved