Methods for the determination and speciation of selenium and arsenic in complex matrices involving, inductively coupled plasma mass spectrometry (ICP-MS) coupled with high performance liquid chromatography (HPLC) was developed. Selenium species were separated and detected by fluoro-acid ion-pairing chromatography with ICP-MS detection and the arsenic species were separated and detected by anion-exchange chromatography with ICP-MS detection. Selenium-containing nutritional supplements, including commercially available selenium supplements, yeast samples, mushroom and garlic samples were analyzed and the major selenium species was identified and quantified by HPLC-ICP-MS. A novel amino acid, S-(methylseleno)cysteine containing a selenium-sulfur group was identified in selenized yeast. Thermal stability studies of the selenized yeasts and selenium-enriched yeast tablets suggest that S-(methylseleno)cysteine is formed at higher temperatures. In Brassica juncea (Indian mustard) plant shoots and roots various selenium species were identified and quantified, after growing the plants in selenium containing [Se(IV) and Se(VI)] hydroponic media for 40 days. The identification of various organoselenium species in the plant shoots and roots will help elucidate the selenium metabolic pathway in selenium-accumulators. A method was developed for the determination of total selenium in selenium-enriched yeast materials by electrothermal atomic absorption spectrometry (ETAAS) with direct slurry sampling. After establishing that organoselenium species are borohydride active in a flow-injection hydride-generation system, a procedure was developed to determine selenomethionine in yeasts and water samples. Total selenium in enzymatic extracts of yeasts was also determined. An ultrasound-assisted procedure was developed for the extraction of arsenic species from soil standard reference materials, spiked soils and plant material. The extracted arsenic species were separated by anion-exchange chromatography prior to determination by plasma source mass spectrometry. Various arsenic species were identified and quantified in the soil standard reference materials and hydroponically grown Brassica juncea shoots and roots.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-3972 |
| Date | 01 January 2004 |
| Creators | Kahakachchi, Chethaka L |
| 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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