Applications of hydrophobic room temperature ionic liquids in ion-selective optodes

Hydrophobic room temperature ionic liquid (RTIL), trihexyltetradecyl phosphonium bis(2,4,4-trimethylpentyl)phosphinate [THTDP][TMPP] as plasticizer for bulk ion optode membranes was studied. Chromoionophore ETH 5294 was incorporated into the PVC–[THTDP][TMPP] optode for detecting inorganic acids, including HCl, H2SO4, HNO3 and HClO4 based on the coextraction response mechanism. Compared to the optodes prepared with conventional plasticizers, PVC–IL based ones exhibited enhanced selectivity and much improved stability for hydrophilic anions. The leaching of ETH 5294 from polymeric film into HCl and H2SO4 solutions was eliminated when ionic liquid has been used as plasticizer.