Potentiometric determination of Hg (II) by new thiosemicarbazone modified electrode in aquatic environments

In this study, a new carbon paste modified electrode was used for potentiometric determination of mercury (II) ions in aquatic environment. For this purpose, a newly synthesized ligand; N‐Ethyl‐2‐picolinoylhydrazinecarbothioamide (EPHC) was applied for modified carbon paste electrode due to its complexation with mercury ions [1-2]. The Hg2+-EPHC complex formation was studied by spectrophotometry and cyclic voltammetry. Carbon paste electrodes (CPE) were prepared by mixing Different amounts of EPHC and CPE with 10 % of the ligand was selected for electrochemical measurements. Under optimal conditions, the mentioned electrode was used for potentiometric determination of mercury (II) ions in aqueous solutions in the linear concentration range of 3.0 × 10-8 - 1.0 × 10-2 mol L-1 with a limit of detection less than 2.9 × 10-9 mol L-1 [3]. In addition, the electrode Nernst slope of 30.15 (± 0.8) mV / decade over the pH range from 1.5 to 5.0 with a response time of 15 seconds. Several electrodes with same combinations were prepared and applied within the period of time indicated that the proposed sensor has a good stability, repeatability and reproducibility. Application of the electrode to the determination of the Hg2+ in industrial waste water, urban waste water and drinking water, without any interference from the excipients, resulted in acceptable deviation from the stated concentration (RSD=3 %). Comparison of these results with those obtained by flam atomic absorption method shows a good agreement between two methods [4].