Protic Ionic Liquid Based Potentiometric Sensors: High Selectivity Detection of Silver(I) Ions

Protic ionic liquids or protic molten salts (PILs or PMOSs) consist entirely of ions and can undergo almost unlimited structural changes. ILs have been extensively used in the field of electroanalysis due to their high electrochemical stability and ionic conductivity. In this study, the usability of a PMOS as an ionophore was investigated. Firstly, 2-phenylethylammonium benzoate (2PEAB) was synthesized, and then polymer membrane sensors containing this ionophore were prepared. The prepared sensors exhibited very high selectivity towards silver(I) ions. The novel silver(I)-selective potentiometric sensor had a wide linear working range over the concentration range of 1.0 × 10⁻¹–1.0 × 10⁻⁵ M, a low detection limit of 7.14 × 10⁻⁶ M, and Nernstian response of 59.3 ± 3.7 mV/decade. The prepared sensors had a relatively fast response time of <7 s, good reproducibility and a wide pH working range (4.0–10.0). The newly developed silver(I)–selective sensors were used as indicator electrodes for the potentiometric titration of silver(I) ions with sodium chloride and were successfully applied for the determination of silver(I) ion content in various water samples.