TOTAL VOLTAMMETRIC WAVES OF SOLVENTS AT MICROELECTRODES - ELECTROANALYTICAL ASPECTS FOR SIMPLE ALCOHOLS

It is demonstrated that methanol (MeOH), ethanol (EtOH), and propanol (PrOH) as solvents, give well defined and well reproducible anodic voltammetric waves at platinum microelectrodes of radius 5-13 mum. A certain level of supporting electrolyte (LiClO4) is necessary to reach the plateau of the anodic wave in the available instrumental potential window. The dependence of the wave height vs. p (p = (nFvr2/DRT)1/2) follows that predicted by the theory for processes with diffusional transport. For mixtures of methanol and ethanol the height of the total wave depends strongly on the percentage of the components, and this dependence resembles a negative zeotrop plot. The total wave height of methanol fits the steady state equation, I = 4nFDrc, where D is the self-diffusion coefficient, c = 24.7 mol l-1 and n = 0.51. In ethanol, impurities such as methanol and water increase the total wave height and therefore it is possible to construct pseudo-waves of these compounds. The heights of the pseudo-waves were linear vs. concentration.