Synthesis and characterization of N,N′-bis(benzophenone imine)formamidine as ionophores for silver-selective electrodes

A novel carbon paste ion selective electrode which was based on a newly synthesized N,N′-bis(benzophenone imine)formamidine (b-BPEF) as an ionophore was prepared for the determination of silver ion. (b-BPEF) was characterized by elemental analysis, FT-IR, 1H NMR, 13C NMR spectroscopy and X-ray single crystal diffraction. The modified electrode with optimum composition, exhibited an excellent Nernstian response to Ag+ ion ranging from 2.2 × 10−7 to 2.2 × 10−2 mol L−1 with a detection limit of 5.0 × 10−8 mol L−1 and a slope of 59.54 ± 0.2 mV decade−1 over a wide pH range (2.0–9.0) with a fast response time (<10 s) at 25 °C. The interaction between (b-BPEF) and Ag+ was studied spectrophotometrically exhibiting the stoichiometry of the complex (1:1) in methanol solution. The proposed electrode showed a fairly good selectivity toward Ag+ ion in comparison with some alkali, alkaline earth, transition and heavy metal ions. This carbon paste electrode was applied as an indicator electrode in potentiometric titration of Ag+ and in direct determination of silver (I) ion in the mineral water and medicinal sample.