Modified random assembly of microelectrodes for the selective electrochemical detection of dopamine

A microelectrode assembly of carbon microdisks (RAM electrode) has been use d for the electrochemical detection of dopamine in the presence of high con centrations of homovanillic, dihydroxyphenylacetic and ascorbic acids. It i s demonstrated that the electroanalytical detection limit (50 nM dopamine) is enhanced compared to results obtained at conventional macrosized carbon electrodes. The surface of carbon microdisks assemblies has been successful ly coated by cation exchangers such as Nafion and laponite. Laponite coatin gs proved to have a higher sensitivity than Nafion films for dopamine detec tion. Overlapping of anionic interferents is overcome by depositing mixed c oatings of Nafion and laponite. Using chronamperometry, due to the attracti ve combinations of permselective ion-exchange and antifouling properties of (Nafion + laponite)-films at the RAM electrodes, it is demonstrated that d iscrimination between dopamine and high concentrations of ascorbic acid is achieved.