ELSEVIER Talanta 45 (1997) 249-255 Talanta Ion-selective electrode for bismuth(III) in ethylenediamintetraacetate medium Marcos Fernando de Souza Teixeira, Alexandre Zambon Pinto, Orlando Fatibello-Filho * Laborat~'~rio de Quimica Analitica, Departamento de Quimiea, Centro de Cifncias Exatas e de Tecnologia, Universidade Federal de Sdo Carlos, Caixa Postal 676. 13560-970 Sdo Carlos-SP, Bra:il Received 8 October 1996; received in revised form 21 February 1997; accepted 25 February 1997 Abstract A coated graphite-epoxy ion-selective electrode for bismuth(Ill), based on the ion-pair between the [Bi(EDTA)] anion and tricaprylylmethylammonium cation (Aliquat 336S) incorporated onto a poly(vinylchloride) (PVC) matrix is constructed. A thin membrane film of this ion-pair, dibutylphthalate (DBPh) or ortho-nitrophenyloctylether (o-NPOE) in PVC was deposited directly onto a Perspex® tube which contained a graphite-epoxy conductor substrate attached to the end of a glass tube. The coating solution was prepared by dissolving 30% (w/w) of PVC in 10 ml of tetrahydrofuran following addition of 65% (w/w) DBPh or o-NPOE and 5% (w/w) of the ionic pair. The effect of pH, EDTA concentration and some cation and anion on the electrode response is investigated. The bismuth(III) ion-selective electrode shows a linear response in the bismuth(III) concentration range from 1.0 x 10 s to 1.0x 10 ~ tool 1 1 and 1.0x 10 -7 to 1.0x 10 ~ mol 1 1 and a slope of 56.8 and 59.2 mV dec. l for the polymeric membranes containing DBPh and o-NPOE, respectively. The lifetime of this electrode was superior to 1 year (over 1600 determinations for each polymeric membrane), with practical detection limits of 6.3 × 10 -9 and 4.4 x 10 8 mol 1-~ with these plasticizers. Application of this electrode with bismuth(III) determination in a stomach anti-acid sample is described. © 1997 Elsevier Science B.V. K~;vwords: Coated graphite-epoxy ion-selective electrode: Bismuth(III); Potentiometry 1. Introduction The determination of bismuth in pharmaceuti- cal compounds is very important, mainly for its control in treatment of patients with gastrointesti- nal disease. Its determination is routinely per- * Corresponding author. Fax: + 55 16 2748350; E-mail: doff@power.ufscar.br formed by gravimetric [1], volumetric [2], spectrophotometric [3] and amperometric [4] methods. The chemistry of metal complexes has con- tributed in the development of ion-selective elec- trodes and amplification in the analysis of multivalent metallic cations species. Ohzeki and Kambara [5] constructed an ion-selective elec- trode for bismuth(III) based on the ion-pair tri- 0039-9140/97/$17.00 ,~ 1997 Elsevier Science B.V. All rights reserved. Pll S0039-91 40(97)001 27-6