Zn²⁺PVC-based Membrane Sensor Based on 3-[(2-Furylmethylene)amino]-2-thioxo-1,3-thiazolidin-4-one

The 3-[(2-furylmethylene)amino]-2-thioxo-1,3-thiazolidin-4-one (FTT) was used as an excellent ionophore in construction of a <TEX>Zn²⁺</TEX> PVC-based membrane sensor. The best performance was obtained with a membrane composition of 30% poly(vinyl chloride), 62% nitrobenzen (NB), 3% FTT and 5% sodium tetraphenyl borate (TBP). This membrane sensor shows very good selectivity and sensitivity towards <TEX>Zn²⁺</TEX> over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The membrane sensor revealed a great enhancement in selectivity coefficients for <TEX>Zn²⁺</TEX> ions, in comparison to the previously reported <TEX>Zn²⁺</TEX> membrane sensors. Theoretical studies also showed the selective interaction of TFF and <TEX>Zn²⁺</TEX> ions. The proposed membrane sensor exhibits a Nernstian behavior (with slope of 29.3 <TEX>±</TEX> 0.3 mV per decade) over a wide concentration range (1.0 <TEX>×</TEX> <TEX>10⁻⁶</TEX>-1.0 <TEX>×</TEX> <TEX>10⁻²</TEX>) with a detection limit of 8.5 <TEX>×</TEX> <TEX>10⁻⁷</TEX> M (52 ng mL<TEX>⁻¹</TEX>). It shows relatively fast response time, in the whole concentration range (<TEX><</TEX> 20 s), and can be used for at least 10 weeks in a pH range of 3.0-7.0. The proposed membrane sensor was successfully used in direct determination of <TEX>Zn²⁺</TEX> ions in wastewater of industrial zinc electroplating companies, and also as an indicator electrode in titration with EDTA.