Ionic liquids based on quaternary phosphonium cation as active components of solid-state iodide selective electrode

The two ionic liquids (ILs) which melt above room temperature were used as active components of solid-state ion-selective electrodes (ISEs). The both ILs are composed of quaternary phosphonium cation and fluorinated anion, namely bis(trifluoromethylsulfonyl)imide and hexafluorophosphate. Molten and then solidified ILs were used to cover solid-state screen printed electrodes with an ion-sensing layer. The sensors show the response towards iodide. The addition of tetrakis(tert-butyl)phthalocyaninatocobalt (III) iodide to ion-sensing composition significantly improved the operational characteristics. The resulting ISE demonstrates good sensitivity and detection limit: S=−(58.0±0.8) mV/dec, Cmin=6×10−5 М; response time is ca. 15 s. A high selectivity towards iodide over number anions is observed. The ISE could be used for at least a month without any deterioration of signal.