Synthesis of an Amide-Linked Diporphyrin Xanthene as a Neutral Carrier for a Lead(II)-Sensitive Electrode.

The synthesis of a new compound, amide-linked diporphyrin xanthene(ADPX), and its application for preparation of lead(II) ion selective electrodes are described. The electrode was prepared with a PVC membrane combining ADPX as a neutral carrier, 2-nitrophenyl octyl ether (o-NPOE) as a plasticizer and sodium tetraphenylborate (NaTPB) as an additive in the percentage ratio of 3:3:65:32 (ADPX: NaTPB: o-NPOE: PVC, w:w). The electrode exhibited linear response with a near Nernstian slope of 28.2 mV per decade within the concentration range of 2.6×10-6 to 1.0×10-1 M lead ions, with a working pH range from 4.5 to 7.5, and a fast response time of less than 30 s. Selectivity coefficients for Pb(II) relative to a number of interfering ions were investigated. The electrode is highly selective for Pb2+ ions over a large number of cations. Several electroactive materials and solvent mediators have been compared and the experimental conditions were optimized. The sensor was applied as indicator electrode in titration of Pb(II) with potassium chromate solution with satisfied results. [ABSTRACT FROM AUTHOR]