Polymers for Inclusion of Redox Mediators

The selective interaction of the coating with the analyte can be exploited for speciation, allowing the quantification of one specific chemical species under which the analyte is present [4]. On the other hand, coatings containing an ion-exchange polymer can drastically reduce the effects of interferences, thanks either to size or to electrostatic exclusion effects [5-8]. 

Tosflex represents the cationic homologous of Nafion , bearing quaternary ammonium residues [2, 4, 9, 10, 12, 13] for instance, Tosflex is suitable for the detection of heavy metals in the form of anionic complexes. 

Besides heavy metal determination, many different organic and inorganic ionic species, such as organic acids and catecholamines, have been quantified by taking advantage of the ability to pre-adsorb them at the electrode surface [8-10]. 

In addition to the two polymers listed above, several electroanalytical applications have been reported for poly(sodium-4-styrenesulphonate) [1], poly(L-lysine) [14], poly(allylamine hydrochloride) [15] and poly(diallyldimethylammonium) chloride [3]. However, due to the higher density of ion-exchange sites in these polymers, they are all characterized by a higher solubility in water, negatively affecting the stability of the anchoring. More stable systems can be obtained by cross-linking stabilization procedures, (Mice the polyelectrolyte is deposited on the electrode surface [1, 14, 16]. 

The ability of ion-exchange polymers to incorporate different i(Mis can be exploited in a different context, i.e., to fix redox active species capable of activating electr(x atalytic processes, i.e., to act as redox mediator, for the determination of a target analyte. The most spontaneous choice consists of the inclusion of 

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