Synthesis of thiophene-2-carbaldehyde-(7-methyl-1,3-benzothiazol-2-yl)hydrazone and its application as an ionophore in the construction of a novel thulium(III) selective membrane sensor

In this work we describe the construction, performance, and applications of a novel thulium(III). The sensor is based on thiophene-2-carbaldehyde-(7-methyl-1,3-benzothiazol-2-yl)hydrazone (TCMH), which acts as an excellent carrier, when used in plasticized poly (vinyl chloride) PVC matrix. The influences of different parameters like the membrane composition and pH of the sample solution on the potentiometric response of the sensor were also studied. Having a lower detection limit of 8.0 × 10−6 M, the sensor response for Tm(III) ion is Nernstian over a wide concentration range of 3 decades of concentration (1.0 × 10−5-1.0 × 10−2 M). The response time of the electrodes is less than 7 s, depending on the concentration of thulium(III) ions. The life time of the sensor was found to be about 7 weeks, during which its potential response does not show any considerable divergences. The sensor revealed very good selectivity for Tm(III) in the presence of several metal ions. The optimum responses were found with membrane composition of 30% PVC, 58% nitrobenzene (NB) as solvent mediator, 7% TCMH, and 5% sodium tetraphenyl borate (NaTPB). In order to investigate the sensors analytical applicability, it was tested as an indicator electrode in both the forward and backward potentiometric titration of Tm(III) and EDTA solutions, with standard EDTA and Tm(III) solutions, respectively, where the results showed to be satisfactorily acceptable.