Improved performance of Prussian blue solid contact allowing flow injection amperometric detection of potassium ions in the excess of sodium

Abstract

Catalytically synthesized Prussian blue nanoparticles are a versatile solid contact for potassium and sodium ion-selective screen-printed electrodes. The cathodic peak current proportional to cation concentration was registered in flow injection amperometry regime. The ability of K+ to penetrate Prussian blue lattice resulted in 2–4-fold higher response to potassium ions relatively to sodium ions. Such intrinsic selectivity of Prussian blue to potassium provided an order of magnitude higher sensitivity of K+-selective electrodes in comparison to Na+-sensors, based on nanoparticles covered with the corresponding ion-selective membranes. In contrast to other known solid contacts, Prussian blue provides the highest sensitivity of potassium-selective electrodes in an amperometric regime (20–50 mA·cm−2·M−1). Moreover, 1 × 10-6 M is the lowest limit of detection ever achieved for Prussian blue-based ion-selective electrodes. The improved sensitivity and selectivity allowed flow injection amperometric detection of potassium ions in the presence of interfering ions. Despite K+ concentration is approximately 40-fold lower than Na+, sensors are applicable for detection of pathological and normal potassium and sodium ions in blood serum. The sensors designed in this work have opened a new opportunity for analyzing biological fluids with ion-selective electrodes in an amperometric regime.