This paper shows that a voltammetric artefact is observed when quaternary ammonium electrolytes are used for voltammetric analysis in non-polar media. This artefact arises due to the slow desorption of quaternary ammonium ions froth the electrode surface and hence the potential at the outer Helmholtz plane (oHp) becomes sweep rate dependent. It was found that the slower the ion desorption the greater the distortion in the voltammogram. Both anion and cations were found to have an effect on the reversibility of processes both positive and negative of the potential of zero charge (pzc). It is suggested that this artefact can also explain deviations in measured rate constants obtained by different techniques in more polar solvents.