Amperometric Ion-Selective Electrodes Based on Prussian Blue Nanoparticles

We report amperometric solid-contact potassium-selective electrodes based on catalytically synthesized Prussian Blue nanoparticles. Both the films and nanoparticles were able to generate an amperometric response in the flow-injection mode under a constant potential. However, the nanoparticles provided a higher sensitivity than the films. Moreover, the intrinsic permeability of Prussian Blue for potassium ions allowed for selective detection of potassium in comparison to sodium even without an ion-selective membrane. The results of electrochemical impedance spectroscopy were used to manage the sensitivity by controlling the charge transfer resistance for ion-selective membranes of different density. By performing measurements in Bis-Tris as a carrier buffer containing no interfering cations, an additional increase in selectivity was enabled. A record selectivity coefficient logK Na+/K+ of −2.7 for the amperometric flow-injection mode was achieved. The obtained results indicate the prospects for analysis of biological fluids as the Na+/K+ ratio is approximately 20–40.