Thiocyanate-selective electrode based on unsymmetrical benzoN4 nickel(II) macrocyclic complexes

Unsymmetrical benzoN4 nickel(II) macrocyclic complexes have been explored as an ionophore for preparing PVC-based membrane electrodes selective to SCN−. The resulting electrode exhibited the best working concentration range (1.4×10−7–0.1 M) with a Nernstian slope of (−59.7±0.9 mV per decade) in the wide pH range of 3.5–10.5. The proposed electrode has a very fast response time (5 s) and high selectivity for thiocyanate over variety of anions. This sensor was successfully applied as an indicator electrode to potentiometric titration of thiocyanate ion with AgNO3 and for direct determination of the amount of thiocyanate in urine and saliva samples in order to distinguish between smokers and nonsmokers.