Potentiometric Performance of Silver Ion-Selective Electrodes Based on Tridentate Schiff Base Derivatives

To examine the directivity for improving the silver ion discrimination ability of a Schiff base, three kinds of tridentate ligands were synthesized and compared with the similar quadridentate ligand as the silver ionophore. Among the Schiff base derivatives tested, 3-(2-pyridylethylimino)-2-butanoneoxime, having one oxime and a pyridine substituent, was found to be the best ionophore for a silver-ion electrode. The electrode based on this derivative exhibited good silver-ion selectivity, -log KpAogt+,K+ = 3.8, comparable to that of a quadridentate Schiff base, N,N′-bis(2′-hydroxyimino-1′-phenylpropyleden)-1,3-propanediamine, reported previously, except for a pseudo Nernstian response (35.6 mV decade−1) with a wide silver-ion activity change in the activity change from 5.0 × 10−7 to 7.9 × 10−2 mol dm−3.