Enhanced Potentiometric Detection of Hydrogen Peroxide Using a Platinum Electrode Coated with Nafion

The potentiometric response to hydrogen peroxide of a platinum electrode coated with a layer of Nafion is presented. The results show that the Nafion membrane acts as an effective permselective barrier, thus significantly reducing the response to some redox active species, such as ascorbate. Even more interesting, these coated electrodes show a significantly enhanced sensitivity to hydrogen peroxide (H2O2) when the measurements are performed in solutions of high ionic strength. The influence of pH, ionic strength and supporting electrolyte on this enhancement are presented. Under optimized conditions these coated electrodes show a linear dependence with the logarithm of the concentration of H2O2, with sensitivities of -125.1 +/- 5.9mVdecade(-1) (several times higher than the bare electrodes) and a linear range that spans from 10(-5) M to 10(-3) M of H2O2. Preliminary studies suggest that the coupling between the redox potential on the Pt electrode and the Donnan potential of the membrane plays a role on this enhancement. Considering this improved sensitivity, selectivity, stability and linear ranges, this system shows promise as a future platform to build enzyme-based potentiometric biosensors.