Unsymmetrical Tetradentate Schiff Bases Copper (II) Complex as Neutral Carrier for Thiocyanate-Selective Electrode

• Published in: Analytical letters 2007-01, Vol.40 (2), p.369-386
• Main Authors: Luo, E.-P., Chai, Y.-Q., Yuan, R.
• Format: Article
• Language: English
• Subjects: Analysis methods; Analytical chemistry; Applied sciences; Chemistry; Electrochemical methods; Exact sciences and technology; Global environmental pollution; Natural water pollution; neutral carrier; o-hydroxybenzophenone-12-diaminobenzene-pyrrole-2-carbaldehyde; Pollution; thiocyanate-selective electrodes; Unsymmetrical Schiff base; Water treatment and pollution
• ISSN: 0003-2719; 1532-236X
• DOI: 10.1080/00032710600964742

Three kinds of transition metal chelates of unsymmetrical tetradentate Schiff base, o-hydroxybenzophenone-1,2-diaminobenzene-pyrrole-2-carbaldehyde(H 2 L), were synthesized to prepare anion-selective electrodes and their anion response characteristics were investigated. The results show that the performances of the electrodes are considerably influenced by the nature of the central metals. The proposed electrode with the Cu(II)-chelate and cationic additive demonstrated an anti-Hofmeister selectivity sequence with a good selectivity towards thiocyanate in the following order: Thiocyanate>iodide>salicylate>perchlorate>bromide>nitrite>chloride>acetate>fluoride>nitrate>sulfite>sulfate. The electrode had an excellent linear response to thiocyanate from 3.4×10 −7 to 1.0×10 −1  M in phosphate buffer solution at pH 5.0 with a slope of −58.7 mV per decade, a detection limit of 1.6×10 −7  M, and a fast response time within 5 s over the entire concentration series. Spectroscopic techniques and AC impedance were used to investigate the response mechanism to thiocyanate of the membrane doped with Cu(II)-chelate. The preliminary application of the electrode for determination of thiocyanate in wastewater and urine samples is reported.