The highly sensitive and selective electrochernical quantification of neurotransmitters (e.g. doparnine) in the extracellular fluids at the central nervous system has continued to attract considerable attention. The most important problem associated with doparnine quantification is the interference of other electroactive compounds oxidizable atpotentials close to that of doparnine, such as ascorbic acid (AA) and 3,4-dihydroxyphenyl acetic acid (DOP AC). Different strategies have been proposed to overcome this problem.

The goal of this presentation is to describe the perrnselective properties of a melanin-type-polymer obtained by potentiostatization of L-dopa in a phosphate buffer solution pH 7.40 using glassy carbon electrodes (GCE). A critical evaluation of the different experimental conditions on the properties of the polymer grown at GCE such as pH, presence of °2´potentiostatization potential and time, is perforrned.

The polymeric membrane rejects anionic species and al1ow us to obtain a highly selective dopamine quantification even in large excess of its metabolic product, DOP AC and AA. For instance, at 0.70 V the decrease in the oxidation current for AA at the polymermodified electrode is 99.6. Neutral species such as catechol and hydrogen peroxide as well as other cationic species (neurotransmitters) can be oxidized at the surface of the electrode.

The selective rejection of anionic species is of great significance for the development of neurotransrnitter sensorstaking into account that they are positively charged at the physiological pH whileDOP AC and AAarenegatively charged. The excellent properties also open doors to the development of new enzymatic biosensors using oxidases as recognition layer .