Response of PVC membrane ion-selective electrodes to alkylmethylimidazolium ionic liquid cations

Several alkylmethylimidazolium tetraphenylborates (Cnmim-TPB, n = 2–10) were synthesized and explored as ion exchangers in plasticized PVC membranes with very attractive sensing behaviors. And then a series of ion-selective electrodes (ISEs) were prepared and their potentiometric properties were investigated. The proposed electrodes exhibited Nernstian responses to alkylmethylimidazolium-based ionic liquid cations [Cnmim]+. These electrodes were successfully applied in the determination of thermodynamic parameters of ionic liquids in aqueous solutions and in the detection of [Cnmim]+ in tap water and distilled water with satisfactory results. For the as-prepared ISEs, one special and important relationship was observed between the selectivity coefficients and the length of alkyl side chains of interfering cations [Cnmim]+. The proper understanding of this relationship should facilitate the development of new method for the determination of ionic liquids using ISEs.