Utilization of a plasticized PVC optical sensor for the selective and efficient detection of cobalt(ii) in environmental samples.

A novel sensitive, selective, and reversible cobalt(ii) ion optical sensor was prepared by the incorporation of 5-[-carboxyphenylazo]2,4-dihydroxybenzoic acid [CPDB] and sodium tetraphenylborate (NaTPB) in a plasticized polyvinyl chloride (PVC) membrane containing dioctyl adipate (DOA) as a plasticizer. The influence of several parameters such as pH, base matrix, solvent mediator and reagent concentration was optimized. A comparison of the obtained results with those of previously reported sensors revealed that the proposed method, in addition to being fast and simple, provided a good linear range (0.05-45.20 μM) and low detection limit (0.015 μM). Low detection and quantification limits and excellent selectivity in the presence of interfering ions such as Fe, Cu, Ni, Ag, Au, Cr, Cd, Zn, Hg, and SO make it feasible to monitor Co ion content accurately and repeatedly in environmental samples with complicated matrices. The optode was regenerated successfully using 0.3 M nitric acid (HNO) solution while its response was reversible with a relative standard deviation (RSD) lower than 1.9% for seven replicate determinations of 20 μM Co in various membranes. The optode was stable and was stored for at least 15 days without observing any change in its sensitivity.