Thiocyanate: selective membrane electrode based on macrotricyclic binuclear Cu(II)–Schiff base complex
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A highly selective PVC membrane electrode was prepared for thiocyanate (SCN−) determination, based on macrotricyclic binuclear Cu(II)–Schiff base complex as an ionophore. The novel macrotricyclic compound (cryptand) was synthesized by condensation of 4,4′-diamino-dibenzo-18-crown-6 with bis(4-formyl phenyl)terephthalate under high-dilution condition and the structure was confirmed by FT-IR, 1H NMR,13C NMR and MS studies. The Cu(II) complex of the compound was prepared and was examined for use as anion-selective electrode as a carrier which displays an anti-Hofmeister selectivity sequence in following order: SCN− > ClO4 − > NO3 − > CN− > I− > CO3 2− > NO2 − > Br− > Cl− > SO4 2− with a preference for thiocyanate ion over many common anions. The electrode has a linear dynamic range between 1.0 × 10−7 and 1.0 × 10−1 M, with a Nernstian slope of −58.9 mV decade−1 and detection limit of 3.1 × 10−8 M. The working pH range of the sensor was found be in the range of 3.0–8.0. It exhibits a fast response time of 20 s and has a lifetime of about 2 months. Application of the electrode for determination of thiocyanate in waste water samples and in human urine samples have also been demonstrated.
KeywordsAnion selective electrode Binuclear Cu(II) complex Thiocyanate PVC-membrane Macrotricyclic compound
Authors would like to thank UGC New Delhi for financial assistantship. Anish Kumar would like to thank CSIR New Delhi for Senior Research Fellowship. Authors are also grateful to CDRI Lucknow for spectral analysis.
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