Flow injection potentiometric determination of bismuth(III) in anti-acid formulations

A flow injection potentiometric procedure is proposed for determining bismu th(III) in anti-acid formulations. In this work, a tubular electrode coated with an ion-pair formed between [Bi(EDTA)](-) and tricaprylylmethylammoniu m cation (Aliquat 336) in a poly(vinylchloride) (PVC) was constructed and u sed in a single channel flow injection system. The effect of membrane compo sition, pH and flow injection parameter over the Bi(III) tubular electrode response (slope (mV/decade)) was initially evaluated in quintuplicate in 0. 5 mol l(-1) EDTA solution as carrier. The best response (-59.6 +/- 0.9 mV/d ecade) was attained with the 5% m/m ion-pair; 65% m/m o-nitrophenyl octyl e ther (o-NPOE) and 30% m/m PVC in pH 6-9. The electrode showed a linear resp onse to E (mV) versus log [Bi(EDTA)](-) in the bismuth(III) concentration r ange from 2.0 x 10(-5) to 1.0 x 10(-2) mol l(-1) and a useful lifetime of a t least 5 months (more than 1000 determinations for each polymeric membrane ). The detection limit was 1.2 x 10(-5) mol l(-1) and the R.S.D. was less t han 2.0% for a solution containing 5.0 x 10(-4) mol l(-1) bismuth(III) (n = 10). Several species such as Cd(II), Mn(II), Ni(II), Zn(II), Co(II), Cu(II ). Mg(II), Cr(III) and AI(III) at 1.0 x 10(-3) mol l(-1) concentration in 0 .5 mol l(-1) EDTA solution did not cause any interference. The frequency ra te was 90 determinations per hour and the results obtained for bismuth(III) in anti-acid formulations using this flow procedure and those obtained usi ng a spectrophotometric procedure are in agreement at the 95% confidence le vel. (C) 2001 Elsevier Science B.V. All rights reserved.