A PVC-based membrane electrode for nickel (II) ions incorporating a tetraazamacrocycle as an ionophore

Dibenzo[e,k]-2,3,8,9-tetraphenyl-1,4,7,10-tetraazacyclododeca-1,3,5,7,9,11-hexaene has been explored as an electroactive material for the fabrication of a poly(vinyl chloride)-based membrane electrode for selective determination of Ni2+ ions. The optimized membranes incorporating [Ph4Bzo2(12)hexaeneN4] as an ionophore, sodium tetraphenylborate (NaTPB) as an anion excluder and dioctylphthalate (DOP), dibutylphosphonate (DBBP), tris(2-ethylhexyl)phosphate (TEHP) and 1-chloronaphthalene (CN) as solvent mediators were prepared and investigated for their response towards Ni2+ ions. The best performance was observed with the membrane having 1.7% ligand, 34.8% PVC, 62.7% DOP and 0.8% NaTPB, and it worked well in a wide concentration range of 3.98 × 10−6 to 1.00 × 10−1 M with a Nernstian slope of 29.5 mV per decade of activity between pH 2.5 and 7.7. The electrode exhibited a detection limit of 2.98 × 10−6 M and a fast response time of 8 s, and was used over a period of 4 months with good reproducibility (S = 0.2 mV). The selectivity coefficient over mono-, di- and tri-valent cations indicated excellent selectivity for Ni2+ ions over a large number of cations. Anions such as Cl− and SO42− did not interfere and the electrode worked satisfactorily in partially non-aqueous media. It could be used successfully for determination of Ni2+ in real samples.