Highly Selective Thiocyanate PVC Membrane Electrode based on Ni (II) Complex of 2-Acetyl Thiophene Thiosemicarbazone Schiff Base (NATS) as Ionophore

Abstract

A highly selective PVC-membrane electrode based on the Nickel (II) complex of 2–acetylthiophene thiosemicarbazone schiff base [Ni(L)2]Cl2 was fabricated and tested as a membrane sensor towards SCN− ions. The newly synthesized 2–acetylthiophene thiosemicarbazone ligand (L) was prepared with the help of 2-acetyl thiophene and thiosemicarbazide hydrochloride. Metal complex was synthesized based on this ligand with NiCl2. The ligand and complex were characterized by the FT-IR, Elemental analysis,1H-NMR and 13C-NMR spectral studies. Ni (II) complex of 2–acetylthiophene thiosemicarbazone was then used as a good sensing material for preparing thiocyanate ion selective PVC membrane sensor. The proposed potentiometric sensor showed a stable potential response to thiocyanate ion with Nernstian slope of -59.2 ± 0.1 mV decade-1 over a linear concentration range of 1.0 x 10-6 to 1.0 x 10-1M. The response of the developed electrode was independent of pH in the range of 2.5–10.0.The sensor worked well with a short response time of ~10 s and a lifetime of about 6 weeks. The proposed sensor finds application as an indicator electrode in the potentiometric titration of SCN− with Ag+ ions and to determine the concentration of thiocyanate ion in water samples.