Highly thiocyanate-selective membrane electrodes based on the N,N′-bis-(benzaldehyde)-glycine copper(II) complex as a neutral carrier

Some novel PVC membrane electrodes based on N,N′-bis-(benzaldehyde)-glycine metallic complexes of Cu(II), Ni(II), Zn(II) and Co(II) as neutral carriers are described. The results showed that the electrode based on the N,N′-bis-(benzaldehyde)-glycine copper(II) complex [Cu(II)-BBAG] had a near-Nernstian response to the thiocyanate ion ranging from 1.0×10−1 to 9.0×10−7 M in a phosphate buffer solution of pH 4.0 with a detection limit of 7.0×10−7 M and a slope of −57.6 mV/decade at 25°C. The electrode displays an anti-Hofmeister selectivity sequence in the following order: SCN−>ClO−4>Sal−>I−>Br−>NO−2>NO−3>SO2−3>SO2−4>Cl−>H2PO The response mechanism is discussed in view of both AC impedance and UV spectroscopy techniques. The [Cu(II)-BBAG]-based electrode was successfully applied to the determination of the thiocyanate ion in wastewater and human saliva.