A highly selective mercury electrode based on a diamine donor ligand

Abstract

(H 2NCHMeCH 2NH 2)(H 2O) 2HgCl 2 ( I) was synthesised, characterised and used for the fabrication of a potentiometric sensor for Hg 2+ metal ions. Membrane having I as electroactive material, sodium tetraphenyl borate (NaTPB) as an anion excluder, dibutylamine (DBA) as plasticizer in PVC matrix in the percentage ratio of 10:3:150:150 ( I:NaTPB:DBA:PVC) (w/w) exhibits a linear response to Hg 2+ ions in a concentration range of 1.25 × 10 −5 to 1.0 × 10 −1 M having a detection limit of 8.9 × 10 −6 with a slope of 25 ± 0.1 mV over the pH range 6.6–9.3. Selectivity coefficients for Hg(II) relative to a number of interfering ions were investigated. The electrode is highly selective for Hg 2+ ions over a large number of mono-, bi-, and trivalent cations. Normal interferents like Ag + and Cd 2+ do not interfere in the working of the electrode. The electrode has also been used successfully in mixtures having a 10% (v/v) methanol and acetone content without showing any considerable change in working concentration range or slope. These electrodes have been found to be chemically inert showing a fast response time of 10 s and were used over a period of 4 months with good reproducibility ( s = ±0.2). The electrode was used for determination of mercury in binary mixtures with 100% recovery and thus the proposed sensor can be used for real sample analysis.