Evaluation of Methods for Total Selenium Determination in Yeast

Abstract

The selenium determination in biological materials by the classical fluorometric method (FM) is time-consuming and also hazardous, as it requires the destruction of the organic matrix samples with hot HNO3/HClO4 mixtures prior to analysis. Accordingly, commercial analytical laboratories are increasingly using faster instrumental methods; for sample digestion, avoid using HClO4. Because of these procedural changes, the results obtained by commercial laboratories may be unreliable, especially for samples containing Se in organic forms. One such "difficult" substrate is Se yeast, which contains most of its Se as selenomethionine. To establish which methods for Se analysis and sample digestion are applicable, samples of Se yeast and of selenomethionine standards were sent to laboratories employing either flame atomic absorption spectrometry (FAAS), inductively coupled plasma-mass spectrometry (ICP-MS), or hydride generation atomic absorption spectrometry (HGAAS). The results were compared with those obtained by FM and non-destructive instrumental neutron activation analysis (INAA). ICP-MS, after microwave digestion of sample with HNO3/H2O2, produced results within 5% of the expected values, as did those obtained by FM and INAA. With FAAS, acceptable results were obtained after digestion with HNO3/HCl. With HGAAS, sample digestion with HNO3/H2O2 produced values that were systematically elevated by about 10% and exhibited standard deviations of > or = 10%. Thus, current methods of sample digestion are applicable for Se yeast analysis by ICP-MS and FAAS, but not by HGAAS.

Utilization of enriched selenium sprouts flour for some cultivars of broad bean to prepare healthy biscuit

“…Samples were digested according to the method described by [23]as follow samples of Se-enriched sprouts (0.5g) were placed in 200×42-mm Pyrex digestion tubes. Concentrated HNO3 (5ml) were added and the mixture heated at 110°C using an electro thermal™ (Electro thermal Engineering Ltd., Essex, UK) heating mantle until foaming subsided.…”

Productivity of some Faba Bean Cultivars and its Pan Bread Characteristics as influenced by Organic Fertilizers under Newly Reclaimed Salinity Sandy Soil

“…Samples were digested according to the method described by Renard and Tompkins (2002). Diluted sample digests were also analyzed in triplicate (Perkin Elmer).…”

Atomic spectrometry update. Clinical and biological materials, foods and beverages

“…Use of aggressive reagents, such as V 2 O 5 , tends to afford the better results. 223,224 Optimised digestion procedures for specific applications seen include those for measuring Se in yeast 226 and Hg in various foods. 227 A rapid automated digestion apparatus was developed by Jacob and Berndt 9 with direct coupling for FAAS.…”

“…Many workers used microwave heating to digest organometallic specimens. Renard and Tompkins, 226 deliberately avoiding the use of HClO 4 , heated yeast with HNO 3 -H 2 O 2 and compared the results then obtained using FAAS, ICP-MS, HGAAS, fluorimetry and NAA. Most were comparable but HGAAS values were higher by about 10%, with high SDs.…”