title: A reflectance flow-through thionine sol-gel sensor for the determination of Se(IV).
abstract: In this work, a reversible sensor to assess the total Se(IV) content in samples is described. Pre-activated glass slides were spin-coated with 100 microL of a 20-h aged sol-gel mixture of 1 mL of tetramethoxysilane, 305 microL of 50 mmol L(-1) HCl and 2.0 mg of thionine. The flow-cell consisted of one of those slides as a window, and was filled with beads of a polystyrene anionic exchange resin to retain Se(IV) in the form of selenite ions. A reflectance transduction scheme at a wavelength of 596 nm was adopted. The cell was coupled to a multicommutation flow system where a programmed volume of a sample solution and 373 microL of 0.4 mmol L(-1) iodide in a 1.6 mol L(-1) HCl solution were sequentially inserted into the cell. The iodine produced from the reaction of retained Se(IV) with iodide bleached the blue color of thionine. Considering a sample volume of 2.30 mL, with which the preconcentration step was minimized, a linear dynamic working range between 1.5 to 20 microg mL(-1) and a detection limit of 0.29 microg mL(-1) were obtained. The sensor enabled us to perform approximately 200 assays, and provided results similar to those of electrothermal atomic absorption spectrometry.
authors.affiliation: REQUIMTE, Dep. Química-Física Fac. Farmácia U. P., R. Aníbal Cunha 164, 4099-030 Porto, Portugal.
authors.forename: Joana A E
authors.initials: JA
authors.lastname: Carvalhido
authors.forename: Agostinho A
authors.initials: AA
authors.lastname: Almeida
authors.forename: Alberto N
authors.initials: AN
authors.lastname: Araújo
authors.forename: Maria C B S M
authors.initials: MC
authors.lastname: Montenegro
mesh_terms: D002623:Chemistry Techniques, Analytical / Q000295:instrumentation*; D005898:Glass / Q000737:chemistry; D044367:Phase Transition; D010640:Phenothiazines / Q000737:chemistry*; D018038:Sodium Selenite / Q000032:analysis* / Q000737:chemistry
chemical_list: D010640:Phenothiazines; D018038:Sodium Selenite; C009469:thionine