A NEW TYPE OF THIN-LAYER MICROELECTRODE FOR INVIVO VOLTAMMETRY - ELECTROOXIDATION OF DOPAMINE, DOPAC AND ASCORBIC-ACID

In the in vivo investigation of neuronal activity, one important point is connected with the determination of extracellular levels of neurotransmitters. A newly designed thin-film microelectrode array was used to investigate the electro-oxidation of dopamine, DOPAC and ascorbic acid in various concentrations. The thin-film microelectrode consisted of a Ag/AgCl reference electrode in the middle of the array, circularly surrounded by an annular space gold working electrode. The counter electrode was another gold ring concentric to the working electrode. Thin-film photolithographic techniques were used for the preparation of this electrode array. With this electrode it is possible to determine the concentration of dopamine in the range between 5 and 100 μmol/l in the presence of ascorbic acid and DOPAC. The electroactive species can be distinguished by different half-wave potentials, e.g. dopamine is oxidized in a potential range between 150 and 200 mV/(Ag/AgCl) and DOPAC in a potential range between 500 and 650 mV/(Ag/AgCl). Some other substances like homovanillic acid, uric acid or serotonine are also oxidizable at the electrode. © 1990.