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New Techniques And New Methods For The Speciation Analysis Of Chemical And Biological Selenium Species

Posted on:2004-09-13Degree:DoctorType:Dissertation
Country:ChinaCandidate:F XuFull Text:PDF
GTID:1101360095462657Subject:Analytical Chemistry
Abstract/Summary:PDF Full Text Request
Selenium as an essential bio-trace element, plays a necessarily living role for the health of human beings. It has long been established that a dietary lack of Se could be related to many diseases, e.g., liver damage, heart attacks, lipids fats oxidazing impair et al. Researches in China has ever efficiently protected and decreased the occurrence of liver cancer by oral supplementation of Na2SeO3. Whereas surplus absorption of Se will lead to toxicity, the range between beneficial and toxic effects in humans is narrow. And selenium in the body may be in many different bio-chemical forms, which determines its metabolic pathways. The biological and toxicological effects of Se are strongly dependent on its species.Recently a necessary requirement to obtain a more detailed insight into the Se cycle in organisms and the contributing bio-transformation processes in the nutritional chain is the development of procedures for trace and micro analysis of Se in biomaterials. Considerably great interests for many concerned fields including biology, chemistry, medicine, and environmental protection science, have been in deep demand for the simple, reliable and sensitive techniques for the analysis of total Se concentration and Se speciation with low detection limits.In order to fit for the requirements above, the emphases of this thesis are to attempt on establishing some new techniques and methods for the analytical detection and speciation of Se species in practical samples. The main contents of this thesis are as follows:(1) Several analytical methods have been developed for the purpose of clearly elucidating living functions of selenium, among these hydride generation (HG) hyphenated with analytical atomic spectrometry offers the advantages of low detection limit and relatively simple instrumentation. However, challenge still remains owing to the losses of Se during sample preparation and the serious interference on the H2Se generation from the coexisting transition metals. The aim of this study is to establish an optimal process for trace Se determination in environ- or bio-samples. Based on our previous studies using alkaline sample-pretreatment for the successive alkaline mode HG, an alkaline fusion procedure is proposed for digesting Se-containing samples. After pre-reduction of Se(VI) to Se(IV) in strong alkaline media, an alkaline mode of HG generation combined with ICP spectrometry for total Se determination was performed. The developed techniqueshave been verified with a National Reference Material (GBW 09142). Several bio- and environ-samples have been analyzed. Bio and environ samples pre-treated by alkaline fusion using NaOH-NaNO3 as digestion agents has the own advantages that (1) prevent Se volatile losses by changing it into selenite(IV) or selenate(VI) salt ions.(2) effectively reduce the possible extra dilution for the aiming detected trace selenium. And the following pre-reduction process for turning Se(VI) into Se(IV) could be accomplished conveniently at room temperature. Also the alkaline mode selenium hydride generation procedures open up the new possibilities of removal of interfering elements (Fe, Cu, Mn et al transition metal ions)in forms of precipitations. The results illustrated that Fe, Cu, Mn concentrations high up to 100μgml-1 could not interfere with 400ngml-1 standard selenite(IV) determination in alkaline mode HG system. The present method was also used successfully for the determination of Se in some practical bio and environ samples. In the future , this reported alkaline fusion-alkaline HG-ICPAES procedure may be applied for identification selenium-containing protein spots in SDS-PAGE or 2D Gel elcetrophoresis bands , as relative experiments are being attempted on in our lab. (2) We explored on the speciation analysis of stepwise hydride generation of Se species. Experimental setup is composed of a home made stepwise generator and ICP spectrometer equipped with charge injection device (CID) detector. The software has a function of continuous measurement of tra...
Keywords/Search Tags:Bio-trace element of Selenium, Hydride generation analytical atomic spectrometry, Bio-chemical speciation, Metabolic absorption, Hierarchical porous zeolite, Immobilized metal-ion affinity chromatography (IMAC)
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