N-Oxyl mediated oxidations are becoming widely applied to the selective oxidation of a range of substrates bearing primary alcohol groups, including renewable biopolymers such as cellulose, but screening of mediators and oxidation conditions can be a laborious process, potentially limiting discovery of new mediators and/or optimised conditions for reaction. We describe a simple method for rapid voltammetric screening of mediators and reaction conditions that requires only small quantities of mediator (so is suitable for screening new synthetic or natural mediators) and yet yields information about relative efficiency of mediator, optimum pH, and preferred buffer identity. Such methodology may be used to speed mediator screening and selection of optimal and greenest reaction conditions prior to preparation, or isolation, of large quantities of mediators.