Sensitive cadmium potentiometric sensor based on 4-hydroxy salophen as a fast tool for water samples analysis

A PVC membrane with 4-hydroxy salophen as an ionophore along with sodium tetraphenyl borate (NaTPB) as an anion excluder and dibutyl phthalate as a solvent mediator in the ratio 28.7:3.3:63.2:4.7 (w/w) (PVC–NaTPB–DBP–ionophore) exhibits good properties with a Nernstian response of 30.1 ± 1.0 mV per decade of activity for Cd(II) ions and a working concentration range of 1.0×10−6–1.0×10−1 mol L−1 Cd(II). The limit of detection was 8.4×10−7 mol L−1 Cd(II). The sensor has a fast response time of 20 s and can be used for at least 8 weeks without any divergence in potential. The electrode can be used in the pH range of 2.8–8.1. The selectivity coefficients for Cd(II) relative to a numbers of potential interfering ions were investigated. The proposed sensor shows fairly good discriminating ability towards Cd(II) ions in comparison with some alkali, alkaline earth, transition and heavy metal ions. The practical utility of the sensor has been demonstrated by using it successfully as an indicator electrode in the potentiometric titration of Cd(II) with EDTA and also for the direct determination of Cd(II) in water and in waste water samples.