Factors influencing the ion-exchange preconcentration and voltammetric behaviour of redox cations at polyestersulfonated ionomer coated electrodes inacetonitrile solutions

Glassy carbon electrodes coated with the poly(estersulfonate) Kodak AQ55 we re used in acetonitrile solutions of various supporting electrolytes to stu dy the ion-exchange voltammetric behaviour of some electroactive cations, n amely the monocharged cation (ferrocenylmethyl)trimethylammonium (FA(+)) an d the dications Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine), methylviologen, but ylviologen and heptylviologen. For all the electroactive cations, it was fo und that the success in their ion-exchange is determined by the size of the supporting electrolyte cation. In particular, lowering the steric hindranc e of the supporting electrolyte cation results in a more significant ion-ex change competition with the electroactive cation. As far as different redox analytes are concerned, it was observed that the preconcentration efficien cy increases with increasing charge and for electroactive species with the same ionic charge, parallels the order of decreasing steric hindrance. In t he case of the viologens, this last factor seems to overcome the hydrophobi c one, where the small (but less hydrophobic) methylviologen is preconcentr ated more efficiently than the large (but more hydrophobic) heptylviologen. (C) 1999 Elsevier Science S.A. All rights reserved.