Analytical Sciences

Highly Selective Thiocyanate Electrode Based on Bis-[N-(2-hydroxyethyl)salicylaldimino]copper(II) Complex as a Neutral Carrier

Xiaoqing HUANG, Yaqin CHAI, Ruo YUAN, Xiuling WANG, and Qunfang LI

College of Chemistry and Chemical Engineering, Southwest China Normal University, Chongqing 400715, China

A novel selective thiocyanate electrode of a PVC membrane based on bis-[N-(2-hydroxyethyl)salicylaldimino]copper(II) [Cu(II)-BNSDM] as a neutral carrier is reported. The selectivity sequence of this electrode is as follows: SCN^- > ClO₄^- > I^- > Sal^- > Br^- > NO₂^- > Cl^- > NO₃^- > H₂PO₄^- > SO₄^2-, which is an anti-Hofmeister selectivity sequence. The electrode exhibits a Nernstian potential linear range to thiocyanate from 1.0 × 10^-1 to 6.0 × 10^-6 mol/L with a detection limit of 2.0 × 10^-6 mol/L and a slope of (-59.0 ± 0.2)mV/decade in pH 5.0 of a phosphate buffer solution at 25°C. Electrochemical impedance spectroscopy (EIS) and UV spectroscopy techniques were performed to understand the response mechanism of the electrode. The electrode had the advantage of simplicity, high selectivity, fast response and low detection limit compared with the other electrode, which had been reported before. The electrode had been applied to wastewater analysis, and the obtained results were satisfactory.

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