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Analytical chemistry of organoselenium compounds by gas chromatography atomic emission detection
Speciation has become an important area of research in the fields of food and environmental analysis because the nutritional value and toxicity of an element depend on its chemical form. For that purpose a Gas Chromatography separation device was used coupled with Atomic Emission Detector (GC-AED) that provided detection for the specific element of interest even though when it may be present in very small amounts or co-elute with other components. ^ The effect of hydrogen and oxygen reagent gases on selenium and sulfur detection using the GC-AED was studied, as well as the helium make-up flow gas. The figures of merit for both selenium and sulfur were studied. In theory, the GC-AED response should be independent of the structure of the compound that is analyzed and only depend on the number of atoms of the element on the plasma. The objective was to determine if the AED response was compound independent for Se and S. In the cases where compound independent calibration behaviour was observed, empirical formula determination was made for that element. ^ In order to study amino acids by GC, they need to be derivatized first in order to make them volatile enough for GC. The derivatization procedure chosen was ethylation by ethylchlroformate because is a simple procedure that derivatizes both amino and carboxylic group in one step. The derivatization parameters, such as amount of reactant, best solvent, reproducibility, extraction yield and effect of interferences were studied. ^ Enriched selenium samples, such as yeast, garlic, bacteria, seeds, and nutritional supplements, were studied. The selenium profile in those samples was compared depending on the sample and the total amount of selenium present. The selenium profile was also compared with the sulfur profile for those samples. Also, different extraction procedures were tried, such as hot water, TMAH, and enzymatic extraction. The percentage of selenium as selenomethionine in the samples was calculated either by external calibration or standard addition. ^ Geochemical samples were also analyzed using the GC-AED and selenium-containing compounds were identified in those samples. ^
Paula B Nolibos,
"Analytical chemistry of organoselenium compounds by gas chromatography atomic emission detection"
(January 1, 2001).
Electronic Doctoral Dissertations for UMass Amherst.