Mixed Aza‐Thioether Crowns Containing a 1,10‐Phenanthroline Sub‐Unit as Neutral Ionophores for Silver Ion

Abstract

AbstractThree different recently synthesized aza‐thioether crowns containing a 1,10‐phenanthroline sub‐unit (L1–L3) and a corresponding acyclic ligand (L4) were studied to characterize their abilities as silver ion ionophores in PVC‐membrane electrodes. Novel conventional silver‐selective electrodes with internal reference solution (CONISE) and coated graphite‐solid contact electrodes (SCISE) were prepared based on one of the 15‐membered crowns containing two donating S atoms and two phenanthroline‐N atoms (L1). The electrodes reveal a Nernstian behavior over wide Ag+ ion concentration ranges (1.0×10−5−1.0×10−1 M for CONISE and 5.0×10−8−4.0×10−2 M for SCISE) and very low limits of detection (8.0×10−6 M for CONISE and 3.0×10−8 M for SCISE). The potentiometric response is independent from pH of the solution in the pH range 3.0–8.0. The electrodes manifest advantages of low resistance, very fast response and, most importantly, good selectivities relative to a wide variety of other cations. The electrodes can be used for at least 2 months (for CONISE) and 4 months for (SCISE) without any appreciable divergence in potentials. The electrodes were used as an indicator electrode in the potentiometric titration of Ag+ ion and in the determination of silver in photographic emulsions and in radiographic and photographic films.