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 characterised in aqueous solutions without and with different concentrations of supporting electrolyte, by using Ru(NH3)(6)Cl-3 as the probe molecule. The experimental results indicate that, with the microelectrode, good quality responses can be obtained under any conditions of ionic strength of the solutions containing the electroactive species. Comparative measurements, carried out with conventional modified carbon disk electrodes under low ionic strength conditions, display voltammograms strongly affected by ohmic drop and capacitive currents. Non-steady state chronoamperometric measurements were used to evaluate the apparent diffusion 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 observed under all the conditions investigated here. The possibility of exploiting the modified microelectrodes for quantitative measurements in solution at low ionic strength has also been ascertained.