Ion-selective electrode for bismuth(III) in ethylenediamintetraacetate medium

Abstract

A coated graphite-epoxy ion-selective electrode for bismuth(III), 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 × 10 −8 to 1.0 × 10 −1 mol 1 −1 and 1.0 × 10 −7 to 1.0 × 10 −1 mol 1 −1 and a slope of 56.8 and 59.2 mV dec. −1 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 × 10 −8 mol 1 −1 with these plasticizers. Application of this electrode with bismuth(III) determination in a stomach anti-acid sample is described.