THE ELECTROCHEMISTRY OF NEUROTRANSMITTERS AT CONDUCTING ORGANIC POLYMER ELECTRODES - ELECTROCATALYSIS AND ANALYTICAL APPLICATIONS

The electrooxidation of catechols, catecholamines and NADH at conventi onal electrode materials is generally characterized by high degrees of irreversibility as well as strong adsorption and, hence, fouling by r eactants and/or products of the reactions. On the contrary, the rates of the electron transfer are highly catalysed by the use of conducting polymer films, such as poly(3-methylthiophene), polyphenylene, polyan aline and polypyrrole, as described here. Furthermore, the usual fouli ng problems are eliminated. Even interference from electroinactive lar ge proteins, such as haemoglobin, and other surfactants are substantia lly reduced. Also, electron spectroscopy for chemical analysis, energy -dispersive analysis of X-rays, theoretical diffusion coefficient calc ulations, metal ion coordination, solution diffusion analyses of cycli c voltammograms etc. show that the electron transfer occurs at the pol ymer-solution interface and not at the inert electrode substrate surfa ce after diffusion through the polymer matrix or through pores. The an alytical application of these polymer electrodes as amperometric detec tors for flow injection analysis and high performance liquid chromatog raphy are given. In addition, selective potentiometric electrodes for catecholamines based on conducting polymer films of crown ethers, such as binaphthyl-20-crown-6, dibenzo-18-crown-6, etc., have been develop ed and characterized. These potentiometric detectors significantly dec rease the usual interferences of ascorbic acid, uric acid and acetamin ophen found in amperometric detection.