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-[ o -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 3+ , Cu 2+ , Ni 2+ , Ag + , Au 3+ , Cr 3+ , Cd 2+ , Zn 2+ , Hg 2+ , and SO 4 2- make it feasible to monitor Co 2+ ion content accurately and repeatedly in environmental samples with complicated matrices. The optode was regenerated successfully using 0.3 M nitric acid (HNO 3 ) solution while its response was reversible with a relative standard deviation (RSD) lower than 1.9% for seven replicate determinations of 20 μM Co 2+ in various membranes. The optode was stable and was stored for at least 15 days without observing any change in its sensitivity.