title: Flow injection potentiometric determination of bismuth(III) in anti-acid formulations.
abstract: A flow injection potentiometric procedure is proposed for determining bismuth(III) in anti-acid formulations. In this work, a tubular electrode coated with an ion-pair formed between [Bi(EDTA)](-) and tricaprylylmethylammonium cation (Aliquat 336) in a poly(vinylchloride) (PVC) was constructed and used in a single channel flow injection system. The effect of membrane composition, 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/decade) was attained with the 5% m/m ion-pair; 65% m/m o-nitrophenyl octyl ether (o-NPOE) and 30% m/m PVC in pH 6-9. The electrode showed a linear response to E (mV) versus log [Bi(EDTA)](-) in the bismuth(III) concentration range from 2.0x10(-5) to 1.0x10(-2) mol l(-1) and a useful lifetime of at least 5 months (more than 1000 determinations for each polymeric membrane). The detection limit was 1.2x10(-5) mol l(-1) and the R.S.D. was less than 2.0% for a solution containing 5.0x10(-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 Al(III) at 1.0x10(-3) mol l(-1) concentration in 0.5 mol l(-1) EDTA solution did not cause any interference. The frequency rate was 90 determinations per hour and the results obtained for bismuth(III) in anti-acid formulations using this flow procedure and those obtained using a spectrophotometric procedure are in agreement at the 95% confidence level.
authors.affiliation: Grupo de Química Analitica, Centro de Ciências Exatas e Tecnologia, Departamento de Química, Universidade Federal de São Carlos, Caixa Postal 676, CEP 13.560-970 -- São Carlos, SP, Brazil.
authors.forename: M F
authors.initials: MF
authors.lastname: Teixeira
authors.forename: O
authors.initials: O
authors.lastname: Fatibello-Filho
mesh_terms: D000863:Antacids / Q000032:analysis*; D001729:Bismuth / Q000032:analysis*; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D004867:Equipment Design; D017022:Flow Injection Analysis / Q000295:instrumentation; D011199:Potentiometry
chemical_list: D000863:Antacids; D001729:Bismuth