Development of 5,5'-Bi(1,10-Phenanthroline)-Based PVC Membrane Potentiometric Sensor for Silver Determination

In this study, the selectivity of the 5.5'-bi(1,10-phenanthroline) Compound (1) against Ag⁺ ions as a chemical sensor was investigated by both absorption and potentiometric methods. First, a 1 × 10^-5 M solution of Compound (1) in acetonitrile was prepared. For the selectivity test, 1 × 10^-2 M solutions of metal ions in acetonitrile were prepared. UV-visible absorption measurements were performed by adding metal ions to a 5.5'-bi(1,10-phenanthroline) compound at certain concentrations. Among the studied metal ions, it was found to be selective only against silver ions. In addition, solid-state contact polyvinylchloride (PVC) membrane electrodes prepared using 5.5'-bi(1,10-phenanthroline) as an ionophore were found to be selective against Ag⁺ ions among other ions. The optimum membrane composition of the measurement was determined as 3% 5.5'-bi(1,10-phenanthroline) + 32% PVC + 64% o-nitrophenyl octyl ether (o-NPOE) + 1% potassium tetrakis(4-chlorophenyl) borate (KTpClPB). The potentiometric properties of the silver selective electrode were determined as linear working range 1.0 × 10^-7-1.0 × 10^-3 M, detection limit 1.0 × 10^-7 M, pH working range 3.23-9.08, and response time 3 s. Absorption and potentiometric methods confirm the selectivity towards silver ions. The IRC analysis of the silver-containing complex, performed using the DFT/B3LYP method with the LanL2DZ basis set, reveals an activation energy of approximately 0.002 Eh, with the transition state energy at -1.433173 Eh.