Schiff Base Impregnated Plasticized Polyvinyl Chloride Optical Sensor for Selective and Efficient Detection of Copper (II) Ion: Central Composite Design

In this paper, a novel selective, sensitive, and reversible copper (II) ion optical sensor was prepared based on the impregnation of N, -bis (2-hydroxynaphthaldehyde)-1, and 3-phenylenediimine (HNPD) into plasticized polyvinyl chloride (PVC) film. The optimal values of pH and response time at which the maximum performance of prepared optical sensor is achieved were found to be 6 and 2 min, respectively. After the optimization of pH and response time, small central composite design (CCD) and desirability function were applied to evaluate the effects of variables including amount of dibuthylphthalate, anion excluder (sodium tetraphenylborate), PVC, and HNPD content on the sensor as figures of merit. The possible interactions between the variables were also investigated using the CCD. Low detection limit and good selectivity in presence of other ions such as Fe³⁺, Ag²⁺, Cr³⁺, Zn²⁺, Hg²⁺, and SO₄²⁻ make it feasible to accurately and repeatedly monitor Cu²⁺ ions content in real samples with complicated matrices. The optode was successfully regenerated by its exposure in 0.1 mol/L of ethylenediaminetetraacetic acid solution while its response was reversible with the relative standard deviation lower than 1.5%. This optode was stable and stored for at least 17 days without observing any change in its sensitivity.