Mercury selective potentiometric sensor based on low rim functionalized thiacalix [4]-arene as a cationic receptor

A novel potentiometric mercury(II) sensor based on the use of cation receptor 5,11,17,23-tetra-tert-butyl-25,27-dihydroxy-26,28-bis(O-methyl glycylcarbonylmethoxy) thiacalix [4]-arene in poly(vinyl chloride) (PVC) matrix for detection of Hg^{2 +} has been developed. The sensor exhibits best performance with a membrane composition of PVC:o-NPOE:ionophore:NaTPB of 60:120:5:10 (%, w/w). The sensor selectively used for determination of mercury ions is in the concentration range 5.0 × 10^{- 8}-1.0 × 10^{- 2} M with a lower detection range of the order 1.0 × 10 ^{- 8} M and a Nernstian compliance of (29.5) within pH range 6.0 to 7.5 and fast response time of 10 s. Influence of the membrane composition and possible interference of other ions have also been investigated on the response properties of the sensor. Fast and stable response, good reproducibility and long-term stability of the sensor are demonstrated. It has been observed that the developed sensor satisfactorily works in partially non-aqueous media up to 10% (v/v) content of methanol and acetonitrile and could be used for a period of 2.5 months. Selectivity coefficients determined with fixed interference method (FIM) and match potential method (MPM) indicate high selectivity towards mercury(II) ions. The proposed electrode shows fairly good discrimination of mercury from other cations. The developed mercury ion-selective electrode can be successfully employed as an indicator electrode in potentiometric titration with EDTA.