Fabrication of a mercury(ii) ion selective electrode based on poly-o-toluidine–zirconium phosphoborate

Abstract

This work covers various aspects of a new ion selective electrode for mercury(II) ions, designed by incorporation of poly-o-toluidine (PTD) into zirconium phosphoborate (ZrPB) ion exchanger. The designed sensor showed pretty good detection ability towards Hg²⁺ ions in comparison to alkali, alkaline earth, transition and even some heavy metal ions. The crystallinity and morphology of the synthesized composite has been explored using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. A linear near Nernstian response for Hg(II) ions with a slope of 28.0 mV per decade over a wide concentration range (1 × 10⁻⁷ M to 1 × 10⁻¹ M) has been observed. The limit of detection is 7.08 × 10⁻⁸ M (0.014 ppm). Moreover, the electrode showed significantly the same results in the pH range 2.5–10.0, a fast response time of 6 s and a life-time of at least 6 months without any divergence in potential. It has been successfully applied as an indicator electrode in potentiometric titrations, and quantitative estimation of Hg(II) ions in tap water, CFL unit waste water and thermometer unit waste.