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Method development and optimization for the determination of selenium in bean and soil samples using hydride generation electrothermal atomic absorption spectrometry
Authors:Shaltout Abdallah A  Castilho Ivan N B  Welz Bernhard  Carasek Eduardo  Martens Irland B Gonzaga  Martens Andreas  Cozzolino Silvia M F
Institution:a Departamento de Química, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, SC, Brazil
b Spectroscopy Department, Physics Division, National Research Center, El Behooth Str., 12622 Dokki, Cairo, Egypt
c Physics Department, Faculty of Science, Taif University, 21974 Taif, P.O. Box 888, Saudi Arabia
d Instituto Nacional de Ciência e Tecnologia do CNPq, INCT de Energia e Ambiente, Universidade Federal da Bahia, 40170-115 Salvador, BA, Brazil
e Departamento de Nutrição, Universidade Federal de Pará, Belem, PA, Brazil
f Institute of Inorganic and Analytical Chemistry, University of Technology, Braunschweig, Germany
g Departamento de Alimentos e Nutrição Experimental, Universidade de São Paulo, São Paulo, SP, Brazil
Abstract:The present investigation is the first part of an initiative to prepare a regional map of the natural abundance of selenium in various areas of Brazil, based on the analysis of bean and soil samples. Continuous-flow hydride generation electrothermal atomic absorption spectrometry (HG-ET AAS) with in situ trapping on an iridium-coated graphite tube has been chosen because of the high sensitivity and relative simplicity. The microwave-assisted acid digestion for bean and soil samples was tested for complete recovery of inorganic and organic selenium compounds (selenomethionine). The reduction of Se(VI) to Se(IV) was optimized in order to guarantee that there is no back-oxidation, which is of importance when digested samples are not analyzed immediately after the reduction step. The limits of detection and quantification of the method were 30 ng L−1 Se and 101 ng L−1 Se, respectively, corresponding to about 3 ng g−1 and 10 ng g−1, respectively, in the solid samples, considering a typical dilution factor of 100 for the digestion process. The results obtained for two certified food reference materials (CRM), soybean and rice, and for a soil and sediment CRM confirmed the validity of the investigated method. The selenium content found in a number of selected bean samples varied between 5.5 ± 0.4 ng g−1 and 1726 ± 55 ng g−1, and that in soil samples varied between 113 ± 6.5 ng g−1 and 1692 ± 21 ng g−1.
Keywords:Selenium  Hydride generation-electrothermal AAS  Iridium trapping  Bean samples  Soil samples
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