Fabrication of a Ho3+-PVC membrane sensor based on N-phenyl-2-(thiophen-2-ylmethylene)hydrazinecarbothioamide for determination of holmium ions

In this research, a new poly(vinyl chloride) (PVC) membrane sensor for Ho3+ ion based on N-phenyl-2-(thiophen-2-ylmethylene)hydrazinecarbothioamide (PHC) as an ionophore was prepared. This sensor demonstrated good selectivity and sensitivity towards the holmium ion in comparison with variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The effect of membrane composition and pH on the response properties of the electrode was investigated. In detail, the suggested sensor exhibited a Nernstian behavior (with a slope of 20.4 ± 0.3 mV decade−1) in the range of 1.0 × 10−6 to 1.0 × 10−2 mol/L with a detection limit of 6.2 × 10−7 mol/L. The response time was relatively quick in the whole concentration range (∼5 s). The sensor usage was found to be at least 10 weeks in a pH range of 3.3–10.9. It was successfully applied in determination of fluoride ions in mouth wash preparations.