Speciation of selenium is of interest because selenium is both essential and toxic to humans, depending on the species and amount ingested. Following the discovery in the Clark study that selenium supplementation (in the form of selenized yeast) could reduce the incidence of some types of cancer, selenium-enriched yeast and other materials have been commercialized or proposed as supplements. However, regulation with respect to quality, storage conditions, stability and content of selenium supplements is a problem. The speciation and stability of organoselenium compounds in yeast-based and yeast-free selenium supplement samples have been studied. Enzymatic extraction enabled selenium speciation profiles to be obtained by ion-pair reversed phase high performance liquid chromatography with inductively-coupled plasma mass spectrometry (HPLC-ICP-MS) and gas chromatography with atomic emission detection (GC-AED). Prior to the GC analyses, the extracts were derivatized with ethylchloroformate. Coated fiber solid-phase microextraction (SPME) was used to extract volatile selenium species for determination by GC-AED and GC-mass spectrometry (GC-MS). Total selenium concentrations were obtained by ICP-MS and ICP-optical emission spectroscopy (ICP-OES). Close similarities of speciation were observed between extended storage and brief heating at elevated temperatures of yeast-based selenium supplements. In both cases selenomethionine, the major component in these supplements, was observed to degrade to form S-(methylseleno)cysteine, a sulfur-selenium amino acid, and selenomethionine selenoxide. Selenium concentrations in saliva were determined by electrothermal atomic absorption spectrometry (ET-AAS) and flow injection-atomic absorption spectrometry with hydride generation (FI-HG-AAS). Selenium concentrations were comparable in both methods.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-5010 |
| Date | 01 January 2008 |
| Creators | Amoako, Prince Osei |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
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