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Ανάλυση ανιόντων με φθορισμομετρία ακτίνων Χ

Hatzistavros Vasilios

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Summary

The present thesis is proposing a new method analysis of chemicalspeciation and elemental detection with environmental significance by usinganionic selective membrane and analyzing them with TXRF.Specifically this analytical method include the production andapplication of a mechanism of chemical speciation of elements of PeriodicTable that due to their different chemical forms (mostly oxidation states)behave differently towards their toxicity, bioavailability and its effect on livingorganisms. Also a qualitative and quantitative detection of chemical elementsis presented that have anionic form in water solutions and have importanteffects on living organisms.The above procedure is accomplished by the use of anion selectivemembranes, an analytical tool, which allows the selective bound of thedesirable element on a membrane polymer matrix. This polymer structure(usually PVC or EVA) is immobilized on a quartz and has been enriched withcertain chemical reagents that provide the membrane with ionic activity andselectivity towards their ability to complex several elements (plasticizers,ligands, ionophores, anion exchangers). At the same time it has the ability ofdirect complex of ions from any water solution(distilled, sea water, drinkingwater).The analysis of the membrane was performed by TXRF. Even thoughthis technique offers only elemental analysis, with the specific methodology,the discrimination between different forms of the same element is achieved.Taking into account the small time of sample analysis, the absence ofpretreatment processes and the other advantages that are mentioned below,the specific instrumentation establishes as very practical and useful.At first is presented the procedure followed by the chemical speciationof Chromium. Two of the predomintan species of Chromium in nature are thetrivalent and the exavalent form. The two different oxidation states differ on the affection with the living organisms and particularly to humans. Whilsttrivalent chromium plays a crucial role in nuitrition and is an essential elementfor the formation of insulin and the metabolism of glycose, hexavalent isextremely dangeroys as it is a potential carcinogenic.With the use of anionicand cationic membrane the discrimination and speciation of different forms ofchromium is accomplished.Continuosly is presented the procedure followed for the chemicalspeciation of bromine between its two forms : bromine ions and bromatesones. Bromate ions are a byproduct of the ozonization of drinking water,which is being done in order to extinquish all the pathogenic microbes presentin water. The presence of bromates though is dangeroys because of its toxiceffects. Bromine in adequate concentration in water is not dangerous at all.The 7th section of the project presents the detection process of cationmetallic ions (mostly heave metals) that exist in high concentrations indrinking water (such as copper, zinc) by the use of anionic selectivemembranes. The above procedure is being succeded by the addition in theexamined metal solution of appropriate amount of anionic ligand thatproduces a complex compound with the metal of anionic charge and becauseof its presence the anionic compounds are bound on the membrane.Also several chemical elements that are present in anionic forms inwater solution and have increased environmental interest are being examinedand attached on the selective membrane with the use of particulate ligands.In each experimental section many parameters where examined suchas, PH, proportions of membrane matrix components, size of the membrane,linearity experiments and minimization of the detection limits. All theseparameters are reffered analytically in each chapter that describes theexperimental procedures followed.The results of the present thesis can be used in the development ofnew experimental methods for the determination of chemical speciation anddetection of other chemical elements with increased environmental andanalytical interest as well as finding applications in the discriminationexperiments of elements that are present in organmetallic and ionorganicforms. The superiority of this method towards all know used analytical methods consists in easy use, direct analysis of samples, less expensive andenvironmentally friendly technology very important requirements in our days.

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