Miniaturized Multi-Sensor Chip for Sodium Detection Using Solid-Contact Ion-Selective Electrodes

Miniaturization of solid-contact ion-selective electrodes (SC-ISEs) have emerged as a promising alternative in various applications, including clinical diagnostics, environmental monitoring, and industrial processes. Here, we describe the fabrication of a miniaturized SC-ISE featuring a carbon ink-modified electric contact prepared via a straightforward drop-casting method. This approach enables a simple and scalable manufacturing process for SC-ISEs. The morphology and the electrochemical properties of this carbon-coated electrode have been investigated prior to the deposition of a Na<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ion-selective membrane. The developed Na+–ISEs show linear sensitivity in the range of 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> to 1 M (54 ± 2 mV/decade) and a selectivity coefficient of –4.3, –3.9, –5.2, –4.3 in the presence of K<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup>, NH<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup>, Ca<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup>, and Mg2+, respectively, according to the fixed interference method. This study integrates an easy drop-casting technique with a multi-electrode, chip-based platform. The findings of this study contribute to the growing body of knowledge of ISEs and offer valuable insights for the further advancement of electrochemical sensing technologies.