Fabrication of a highly selective Eu(III) membrane sensor based on a new S–N hexadentates Schiff's base

A novel potentiometric membrane Eu (III) ion sensor is described based on a new S–N hexadentates Schiff's base, bis(thiophenol)butane2,3-dihydrazone (SNSB). The sensor exhibited a Nernstian response over a concentration range of 1.0 × 10−5 to 1.0 × 10−2 M, with a detection limit of 5.0 × 10−6 M. The best performance was achieved with a membrane composition of 30% PVC, 63% o-nitrophenyloctyl ether (NPOE), 5% SNSB, and 5% (0.010 mmol) potassium tetrakis(p-chlorophenyl) borate (KTpClPB). It was found that in the pH range of 3.0–8.5, the potential response of the sensor was not affected by the pH. Furthermore, the electrode presented satisfactory reproducibility, very fast response time (<5 s), and relatively good discriminating ability for Eu(III) ions with respect to many common cations and lanthanide ions, including sodium, potassium, magnesium, calcium, copper, nickel, cobalt, zinc, lead, lanthanum, cerium, gadolinium, samarium, ytterbium, presidium, terbium, neodymium, holmium, erbium, thulium, lutetium, dysprosium, iron and chromium metal ions. The sensor was applied to the determination of fluoride ions in two mouth wash preparations and binary mixtures.