Modified Random Assembly of Microelectrodes for the Selective Electrochemical Detection of Dopamine

A microelectrode assembly of carbon microdisks (RAM electrode) has been used for the electrochemical detection of dopamine in the presence of high concentrations of homovanillic, dihydroxyphenylacetic and ascorbic acids. It is 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 successfully coated by cation exchangers such as Nafion and laponite. Laponite coatings proved to have a higher sensitivity than Nafion films for dopamine detection. Overlapping of anionic interferents is overcome by depositing mixed coatings of Nafion and laponite. Using chronamperometry, due to the attractive combinations of permselective ion-exchange and antifouling properties of (Nafion+laponite)-films at the RAM electrodes, it is demonstrated that discrimination between dopamine and high concentrations of ascorbic acid is achieved.