In-situ preconcentration, and electrochemical sensing of zinc(II) and copper(II) based on ionic liquid mediated hollow fiber-modified pencil graphite electrode using response surface methodology

A single-use electrochemical sensor using ionic liquid mediated hollow fiber-graphite working electrode was fabricated for the first time. The screening tool was developed by coupling this electrode with differential pulse voltammetry (DPV) for in-situ pre-concentration and determination of Zn(II) and Cu(II). In our plot, porous polypropylene hollow fiber membrane was divided into pieces of 2 cm, then fiber's lumen and pores were satiated with homogeneous mixture of reduced graphene oxide (rGO) and three types used ionic liquids:(1-ethyl-3-methylimidazolium tetrafuoroborate), (1-butyl-3-methylimidazoliumhexafluorophosphate) and (1-butyl-2,3-dimethylimidazolium hexafluorophosphate) individually. Thereafter, a pencil graphite rod was placed inside the fiber. Fabricated sensors were used for single-step simultaneous purification and determination of Zn(II) and Cu(II) ions from water samples. The response surface method (RSM) was used as the basis of the design and analysis of the experiments. Parameters that were mostly important in the separation part of the study, such as: molar mass of ionic liquids, amount of nanoparticle and sonication time have been investigated. Analysis of variance (ANOVA) and RSM contour plots were presented for effect of all factors (input parameters) on the maximum current of differential pulse voltammetry (DPV) peaks (output responses). The results disclosed that the metal removal was impressed by the molar mass of ionic liquids, amount of nanoparticle and sonication time respectively. The efficiency specifications of this procedure were evaluated by calculating precision and response linearity. Under the optimal experimental conditions linear concentration ranges of 0.9–550µgL-1 and 0.7–500 µgL-1 were obtained for Zn(II) and Cu(II) ions respectively. The reported limit of detection for Zn(II) and Cu(II) were 0.27 and 0.21µgL-1 with relative standard deviations (RSD) 3.2%, and 4.4%, respectively. In addition, this sensor was successfully applied to real water samples.