Polymeric membrane sensors based on Cd(II) Schiff base complexes for selective iodide determination in environmental and medicinal samples

The two cadmium chelates of schiff bases, N,N′-bis(salicylidene)-1,4-diaminobutane, (Cd-S1) and N,N′-bis(salicylidene)-3,4-diaminotoluene (Cd-S2), have been synthesized and explored as ionophores for preparing PVC-based membrane sensors selective to iodide(I) ion. Potentiometric investigations indicate high affinity of these receptors for iodide ion. Polyvinyl chloride (PVC)-based membranes of Cd-S1 and Cd-S2 using as hexadecyltrimethylammonium bromide (HTAB) cation discriminator and o-nitrophenyloctyl ether (o-NPOE), dibutylphthalate (DBP), acetophenone (AP) and tributylphosphate (TBP) as plasticizing solvent mediators were prepared and investigated as iodide-selective sensors. The best performance was shown by the membrane of composition (w/w) of (Cd-S1) (7%):PVC (31%):DBP (60%):HTAB (2%). The sensor works well over a wide concentration range 5.3 × 10−7 to 1.0 × 10−2 M with Nernstian compliance (59.2 mV decade−1 of activity) within pH range 2.5–9.0 with a response time of 11 s and showed good selectivity for iodide ion over a number of anions. The sensor exhibits adequate life (3 months) with good reproducibility (S.D. ± 0.24 mV) and could be used successfully for the determination of iodide content in environmental water samples and mouth wash samples.