Planar ionic liquid-based reference electrode for potentiometric measurements

Miniaturization is a key trend in analytical chemistry, enabling rapid and cost-effective analysis of small sample volumes. In planar potentiometric sensors, the lack of space for an internal liquid electrolyte has led to the development of all-solid-state electrodes. While considerable progress has been made in all-solid-state ion-selective electrodes, planar reference electrodes remain underexplored.

In this work, polyurethane-based reference electrodes containing ionic liquids were developed and optimized. The results showed that electrode potential stability strongly depends on the difference in partition coefficients of the ionic liquid ions, whereas the ionic liquid content and the presence of a plasticizer have little effect on performance. Optimized membranes were then applied to fabricate all-solid-state reference electrodes on screen-printed transducers, providing stable potentials over a wide range of ion concentrations and during long-term measurements. Finally, complete potentiometric sensor systems for lactate and pH detection were constructed, demonstrating promising sensitivity for both analytes.