Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.22/2982
Título: Citrate selective electrodes for the flow injection analysis of soft drinks, beers and pharmaceutical products
Autor: Ribeiro, Cristina M. F.
Delerue-Matos, Cristina
Sales, M. Goreti F.
Vaz, M. Carmo V. F.
Palavras-chave: Flow injection analysis
Citrate selective electrodes
Polymeric membranes
Potentiometry
Data: 2002
Editora: Elsevier
Relatório da Série N.º: Analytica Chimica Acta; Vol. 471, Issue 1
Resumo: Aiming the establishment of simple and accurate readings of citric acid (CA) in complex samples, citrate (CIT) selective electrodes with tubular configuration and polymeric membranes plus a quaternary ammonium ion exchanger were constructed. Several selective membranes were prepared for this purpose, having distinct mediator solvents (with quite different polarities) and, in some cases, p-tert-octylphenol (TOP) as additive. The latter was used regarding a possible increase in selectivity. The general working characteristics of all prepared electrodes were evaluated in a low dispersion flow injection analysis (FIA) manifold by injecting 500µl of citrate standard solutions into an ionic strength (IS) adjuster carrier (10−2 mol l−1) flowing at 3ml min−1. Good potentiometric response, with an average slope and a repeatability of 61.9mV per decade and ±0.8%, respectively, resulted from selective membranes comprising additive and bis(2-ethylhexyl)sebacate (bEHS) as mediator solvent. The same membranes conducted as well to the best selectivity characteristics, assessed by the separated solutions method and for several chemical species, such as chloride, nitrate, ascorbate, glucose, fructose and sucrose. Pharmaceutical preparations, soft drinks and beers were analyzed under conditions that enabled simultaneous pH and ionic strength adjustment (pH = 3.2; ionic strength = 10−2 mol l−1), and the attained results agreed well with the used reference method (relative error < 4%). The above experimental conditions promoted a significant increase in sensitivity of the potentiometric response, with a supra-Nernstian slope of 80.2mV per decade, and allowed the analysis of about 90 samples per hour, with a relative standard deviation <1.0%.
Peer review: yes
URI: http://hdl.handle.net/10400.22/2982
Versão do Editor: http://www.sciencedirect.com/science/article/pii/S0003267002007560#
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