Solidified ionic liquid as crystalline sensing element of the bromide selective electrode

• Organic ionic solid (solidified ionic liquid, m.p. 78 oC) 1,3-dihexadecylimidazolium bromide was used to create anion-sensing layer on the surface of screen-printed electrode.
• Sensor demonstrates high non-Hofmeister selectivity. Both small, strongly hydrated, and large anions are discriminated. This pattern is in sharp contrast with behavior of conventional PVC membrane electrode containing the same ion-exchanger compound.
• Highly increased selectivity may be attributed to steric discrimination imposed to bulky anions by ionic solid. X-ray powder diffraction confirmed crystalline nature of the solid.

We report on the use of solidified ionic liquid (low-melting ionic solid, m.p. 78 °C) 1,3-dihexadecylimidazolium bromide, [(C16)2Im]Br, as a sensing layer in solid-state ion-selective electrode for bromide. This crystalline material demonstrates high selectivity to the target ion: both too small (strongly hydrated) and too large anions are discriminated. This pattern is in sharp contrast with usual Hofmeister-like series obtained for the sensor based on conventional plasticized PVC membrane containing the same compound, [(C16)2Im]Br.