USE OF NAFION(R) COATED CARBON DISK MICROELECTRODES IN SOLUTION WITHOUT AND WITH DIFFERENT CONCENTRATIONS OF SUPPORTING ELECTROLYTE

Carbon microdisk electrodes modified with Nafion(R) have been characte rised in aqueous solutions without and with different concentrations o f supporting electrolyte, by using Ru(NH3)(6)Cl-3 as the probe molecul e. The experimental results indicate that, with the microelectrode, go od quality responses can be obtained under any conditions of ionic str ength of the solutions containing the electroactive species. Comparati ve measurements, carried out with conventional modified carbon disk el ectrodes under low ionic strength conditions, display voltammograms st rongly affected by ohmic drop and capacitive currents. Non-steady stat e chronoamperometric measurements were used to evaluate the apparent d iffusion coefficient D-app and concentration c(f) of Ru(NH3)(6)Cl-3 in the polymer film. A concentration dependence of D-app has been observ ed under all the conditions investigated here. The possibility of expl oiting the modified microelectrodes for quantitative measurements in s olution at low ionic strength has also been ascertained.