Before attempting to identify the factors that may be most relevant to the variation encountered in the electrode kinetics, it is worthwhile reviewing the electrode pre-treatment regime. A nominally 3 mm diameter GC working electrode was purchased from BAS. Prior to each set of measurements the surface of the GC electrode was thoroughly polished with 0.3 µm alumina powder in the form of an aqueous slurry on a wet polishing cloth (BAS).