Towards solid-state, thick-film K+ and Na+ ion sensors for soil quality assessment

Two types of amperometric sensors for monitoring potassium and sodium ions in soil were developed, using ionophore-doped polymeric membranes to provide selectivity to these ions. The sensors were fabricated by a novel methodology based on thick-film technology that has allowed for the fabrication of small, solid-state and robust sensors, suitable for portable devices. Electrochemical characterization of these sensors has been performed by Cyclic Voltammetry in KCl and NaCl solutions. It was demonstrated that the sensors could successfully detect potassium and sodium ions in the 0.1 mM-20 mM concentration range, with sensitivity of approximately 10 and 7 μA/mM for K
⁺
and Na
⁺
, respectively. Both the potassium and sodium sensors exhibited a significant interference between sodium and potassium ions with the potassium sensors showing higher sensitivity than sodium sensors.