Mohammad Reza Ganjali,^a* Hassan Ali Zamani,^b Parviz Norouzi,^a Mehdi Adib,^a and Mohammad Accedy^c
a Department of Chemistry, Tehran University, Tehran, Iran, E-mail: ganjali@khayam.ut.ac.ir
^b Department of Chemistry, North Tehran branch, Azad University, Tehran, Iran
^c Department of chemistry, Tarbiat Modarres University, Tehran, Iran

Abstract
In this work, a novel calcium PVC-based membrane sensor based on 2-[(2-hydroxyphenyl)imino]-1,2-diphenylethanone (HD) as a new ionophore is presented. The sensor displays a linear dynamic range between 1.0×10^–1 and1.0×10^–6 M, with a near Nernstian slope of 28.5 ± 0.5 mV per decade and a detection limit of 8.0×10^–7 M. The best performance was obtained with a membrane composition of 30% poly(vinyl chloride), 62% nitrobenzene, 5% sodium tetraphenyl borate and 3% HD. The potentiometric response of the proposed electrode is independent of the pH of the solution in the pH range of 4.0 –11.5. The sensor possesses the advantages of short conditioning time, fast response time (<20 s), and especially, very good selectivity towards alkali and alkaline earth, and some mono, di and trivalent cations, such as Li⁺, Na⁺, K⁺, Mg²⁺, Sr²⁺, Ba²⁺, Ag⁺, Cu²⁺, Al³⁺, La³⁺ and Ce³⁺ ions. The electrode can be used for at least 10 weeks without any considerable divergence in the potentials. It was used as an indicator electrode in potentiometric titration of Ca(II) ions with EDTA.