Mercury(II) Ion-Selective Electrodes Based on Heterocyclic Systems

Mercury ion-selective electrodes (ISEs) were prepared with a polymeric membrane based on heterocyclic systems: 2-methylsulfanyl-4-(4-nitro-phenyl)-1-p-tolyl-1H-imidazole (I) and 2,4-diphenyl-1-p-tolyl-1H-imidazole (II) as the ionophores. Several ISEs were conditioned and tested for the selection of common ions. The electrodes based on these ionophores showed a good potentiometric response for Hg²⁺ ions over a wide concentration range of 5.0×10^-5-1.0×10^-1M with near-Nernstian slopes. Stable potentiometric signals were obtained within a short time period of 20 s. The detection limits, the working pH range of the electrodes were 1.0×10^-5 M and 1.6-4.4 respectively. The electrodes showed better selectivity for Hg²⁺ ions over many of the alkali, alkaline-earth and heavy metal ions. Also sharp end points were obtained when these sensors were used as indicator electrodes for the potentiometric titration of Hg²⁺ ions with iodide ions.