Schiff base complexes of Cu(II) and Ni(II) derived from N,N'-bis(salicylidene)-o-phenylenediamine as potential ionophores in the construction of PVC membrane iodide sensors

Two Schiff base compl exes of Cu(II) and Ni(II),designated as M1 and M2, respectively were synthesized from N,N'-bis(salicylidene)-o-phenylenediamine and characterized by IR and NMR spectroscopy. The results of conductometric and stability constant revealed that these complexes with several anions created the possibility of their use as potential ionophores in the development of iodide selective sensors. Poly(vinyl chloride)(PVC) membrane sensors of these complexes using several plasticizers (o-NPOE, CN, TBP, DOP and DBP) and cationic additive (CTAB) were fabricated as well as examined for the detection of iodide ions in aqueous solution. The performance characteristics of the various sensors of these ionophores exhibited that sensors having membrane composition as M1(4 mg):PVC(34 mg):TBP(62 mg):CTAB(7 mg) and M2(4 mg):PVC(34 mg):TBP(62 mg):CTAB(5 mg) showed best characteristics regarding Nernstian slope (59.4 and 59.2 mV decade−1 of [I-]), linear working range (6.3 ×10−8-3.2 ×10−2 mol L−1 and 7.9 ×10−8-1.0 ×10−2 mol L−1), detection limit (3.8 ×10−8 mol L−1 and 5.6 ×10−8 mol L−1) and response time of 7 and 9 s, respectively. These sensors performed well in the pH range of (4.0–9.0) and showed adequate shelf lives with 20% (v/v) non-aqueous tolerance. The proposed sensors served as indicator electrodes in the potentiometric titration of iodide ions against silver nitrate solution and in the determination of iodide ion concentration in mouthwash and river water samples.