A Reflectance Flow-through Thionine Sol-gel Sensor for the Determination of Se(IV)

• Published in: Analytical Sciences 2010/06/10, Vol.26(6), pp.665-669
• Main Authors: CARVALHIDO, Joana A. E., ALMEIDA, Agostinho A., ARAÚJO, Alberto N., Maria C. B. S. M. MONTENEGRO
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Chemistry; Chemistry Techniques, Analytical - instrumentation; Glass - chemistry; Phase Transition; Phenothiazines - chemistry; Sodium Selenite - analysis; Sodium Selenite - chemistry
• ISSN: 0910-6340; 1348-2246
• DOI: 10.2116/analsci.26.665

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 μL of a 20-h aged sol-gel mixture of 1 mL of tetramethoxysilane, 305 μL of 50 mmol L−1 HCl and 2.0 mg of thonine. 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 μL 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 μg mL−1 and a detection limit of 0.29 μg mL−1 were obtained. The sensor enabled us to perform approximately 200 assays, and provided results similar to those of electrothermal atomic absorption spectrometry.