Fabrication of PVC Based Membrane Using Nickel Porphyrazine as Ionophore in the Screening of Thiocyanate Ion in Aqueous and Real Samples

The [Ni{(TAP)(SBn)8}] complex (I), i.e. ({2,3,7,8,12,13,17,18-octakis(benzylthio)-5,10,15,20- tetraazaporphyrin})nickel(II), has been explored as an ionophore for fabrication of the PVC based membrane electrodes used in the screening of thiocyanate anion (SCN-). The membrane having [Ni{(TAP)(SBn)8}] complex (I) as an electroactive material and dioctylphthalate (DOP) as plasticizer in the PVC matrix with the percentage ratio 5 : 158 : 200 (I : DOP : PVC, % w / w) exhibited a linear response in the concentration range 7.0 × 10-6 - 1.0 × 10-1 M of SCN- with a sub-Nernstian slope 32.5 ± 0.2 mV / decade of activity and a fast response time of 10 ± 2 s. The sensor works well in the pH range 3.0 - 9.5 and could be satisfactorily used in presence of 50 % (v / v) methanol, ethanol and acetone, and is selective for SCN- over a large number of anions with slight interference from iodide (I-) and azide (N3-) if present at a level ≥ 1.0 × 10-5 M. Described electrode works well over a period of six months. The sensor can be successfully applied for the screening of SCN- in both aqueous and real samples and also as indicator electrodes in precipitation titrations.