RESUMEN
A biosensor based on the iridium nanoparticles dispersed in ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (Ir-BMI·PF6) and a celery (Apium graveolens) extract as a source of polyphenol oxidase (PPO) was constructed. A modified support based on ß-cyclodextrin (ß-CDEP) was used for enzyme immobilization. The behavior of phenolic compounds was investigated by square-wave voltammetry and rutin was selected by presenting the greatest signal. The best performance was obtained with a composition of 70:10:10:10% (w/w/w/w) of the graphite powder:ß-CDEP:Nujol:Ir-BMI·PF6 composition, a PPO concentration of 500unitsmL(-1), in 0.1M phosphate buffer solution (pH 6.0) with frequency, pulse amplitude and scan increment at 100Hz, 60mV, and 3.0mV, respectively. Under optimized conditions, the cathodic currents increased linearly for the rutin concentration range of 1.3×10(-7)-2.0×10(-6)M with a detection limit of 7.9×10(-8)M. This sensor demonstrated acceptable repeatability and reproducibility and the results for the rutin recovery ranged from 92.8 to 103.4%. A relative error of 0.7% was obtained in the rutin determination in simulated samples.
Asunto(s)
Técnicas Biosensibles/métodos , Catecol Oxidasa/metabolismo , Fenoles/análisis , Apium/enzimología , Técnicas Biosensibles/estadística & datos numéricos , Catecol Oxidasa/química , Técnicas Electroquímicas , Enzimas Inmovilizadas/química , Enzimas Inmovilizadas/metabolismo , Iridio , Nanopartículas del Metal , Modelos Moleculares , Fenoles/química , Reproducibilidad de los Resultados , Rutina/análisis , Rutina/química , beta-CiclodextrinasRESUMEN
A biosensor based on the ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate containing dispersed iridium nanoparticles (Ir-BMI.PF(6)) and polyphenol oxidase was constructed. This enzyme was obtained from the sugar apple (Annona squamosa), immobilized in chitosan ionically crosslinked with oxalate. The biosensor was used for determination of chlorogenic acid by square wave voltammetry. The polyphenol oxidase catalyzes the oxidation of chlorogenic acid to the corresponding o-quinone, which is electrochemically reduced back to this substance at +0.25V vs. Ag/AgCl. Under optimized operational conditions the chlorogenic acid concentration was linear in the range of 3.48x10(-6) to 4.95x10(-5)mol L(-1) with a detection limit of 9.15x10(-7)mol L(-1). The biosensor was applied in the determination of chlorogenic acid in organic and decaffeinated coffee and the results compared with those obtained using the capillary electrophoresis method. The recovery study for chlorogenic acid in these samples gave values of 93.2-105.7%.