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Novel methods for the determination of arsenic, antimoney and selenium in single cell proteinMcCabe, S. January 1986 (has links)
No description available.
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Applications of stripping voltammetry to trace analysisDennis, Bruce Lawrence, 1951- January 1975 (has links)
No description available.
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Selenium and trace metals as pollutantsAl-Attar, A. F. January 1987 (has links)
No description available.
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Speciation of selenium in food supplementsMatni, Gisèle. January 1996 (has links)
Selective isolation protocols of selenium (Se) species integrated to Se specific atomic absorption spectroscopy (AAS) detection were developed and optimized for Se speciation in food supplements, including selenized yeasts. By ultrafiltration, 69.18% of Se in the extract was found as a low molecular weight soluble form, the remaining 30.82% was bound to high molecular weight components. After a cation-exchange chromatography of the ultrafiltrate, 3.77% of the Se in the extract was found in the aqueous washings of the column indicating the presence of free inorganic anions of Se; the 65.41% of Se retained on the column corresponded to the free organic Se cations. The limit of detection for the HPLC-THG-AAS system was 1.85 ng of Se. Se was shown to be widely distributed over all the proteins with one sharp peak corresponding to the free forms of Se. Four major peaks were found at MW $>$ 250 000 Da (15.97% of Se recovered), between 102 330 and 117 490 Da (7.06%), between 48 977 and 53 703 Da (12.71%) and close to the dye migration band (17.25%). / Selective isolation and HPLC-AAS protocols were also developed and optimized for the determination of free organic forms e.g. selenomethionine (SeMet), selenocystine (SeCystine) and inorganic forms of selenium in aqueous solutions, and in complex matrices such as nutritional supplements and mixtures of free amino acids. The selenoamino acid in alkaline solution was first derivatized with 1-fluoro-2,4-dinitrobenzene. After removal of excess of reagent by partitioning with diethyl ether, the N-dinitrophenyl (DNP)-derivatized selenoamino acid was acidified and extracted with diethyl ether. Inorganic Se(IV) was extracted from the acidic aqueous phases by complexation with 1,2-phenylenediamine, forming a piazselenol. Se derivatives were determined selectively by HPLC-THG-AAS. A selective chromatographic mechanism based on $ pi$-electron interactions was optimized using a silica stationary phase derivatized with p-nitrophenyl moieties. Co-injections of DNP-SeMet, DNP-SeCystine and piazselenol save retention times of 3.7, 4.0 and 4.9 min, respectively, using a methanolic mobile phase containing 1.5% triethylamine and 0.013M acetic acid. Primary analytical validation parameters including stability, linearity and limits of detection were obtained using purified DNP-SeMet, DNP-SeCystine and piazselenol standards which were characterized by $ sp1$H-, $ sp{13}$C- and $ sp{77}$Se-NMR analysis and/or fast atom bombardment MS techniques. The calibration graphs for sequential dilutions of these Se standards were linear and the limits of detection from the resultant calibration graphs were 17 ng, 0.21 ng and 18.53 ng of Se, respectively. The purified DNP-SeMet and DNP-SeCystine were found to be photosensitive. The recovery of SeMet, SeCystine and inorganic Se from the stock solutions and/or nutritional supplements was virtually quantitative. In the presence of a 500-fold excess of other amino acids, the recovery of SeMet and SeCystine (96.1 $ pm$ 3.9% and 98.08 $ pm$ 4.2%, respec
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An approach to the improvement of the Selenium analysis process of the Western Cape Provincial Veterinary LaboratoryCloete, Bronwyn Claudia January 2011 (has links)
Thesis (MTech(Engineering))--Cape Peninsula University of Technology, 2011 / Reliable analytical results represent the pinnacle assessment of the quality of an
analytical laboratory. Variability associated with the analytical method, or
process known as selenium analysis which is being used at Western Cape
Provincial Veterinary Laboratory (WC PVL), presents a critical quality problem.
This is due to the narrow margin of safety between toxic and deficient doses for
animal health. In addition, control features of this selenium process, were found
to be limited. Limited control features represent ‘process waste’. To overcome
the adverse impact of variation and limited control, steps towards process
improvement present the best solution.The primary research objective of the research study is: “To establish an
alternative accurate and safer digestion procedure within the ‘selenium analysis
process, in order to attain quality improvement of the process”.The scientific method was employed to accomplish the research objective. The
research design and methodology selected was based on the scientific PDCA
cycle, and is known as Lean Six Sigma. A research hypothesis was set as H0 :
Variation in process, time and control procedures have a direct impact on the
disparity in selenium testing results. Research was able to test the hypothesis
using scientific methodology which was empirical, inductive and deductive,
systematic, relied on data and was fact based.Implementation of an alternative, more reliable and safer selenium analysis
process is believed to result in reduced risks associated to the digestion procedure,
while optimising selenium yield and ultimately translating into improved quality
in terms of accuracy and precision, thus confidence in results.
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Speciation of selenium in food supplementsMatni, Gisèle. January 1996 (has links)
No description available.
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