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Development of Instrumentation and Methodology for Elemental and Speciation Analysis of Arsenic Based on Hydride Generation and on Atomic Fluorescence Spectrometric Detection
Marschner, Karel ; Dědina, Jiří (advisor) ; Kanický, Viktor (referee) ; Spěváčková, Věra (referee)
(EN) The presented dissertation is devoted to hydride generation from arsenic species and its application for speciation analysis based on atomic fluorescence detection. Hydride generation from toxicologically relevant arsenic species was optimized in order to achieve a 100% efficiency. The resulted experimental setup was subsequently used for speciation analysis of arsenic in human urine by high performance liquid chromatography with detection by atomic fluorescence spectrometry. The accuracy of the developed method was verified by comparative analyses of human urine samples collected from five individuals with an independent reference method. The cleavage of As-C bond during the reaction of methylated arsenic species with tetrahydridoborate(1-) (THB) in acidic media was studied in detail. Pronounced demethylation of methylated arsenic species was found during the reaction of THB with HCl, H2SO4, and HClO4 while hydride generation from CH3COOH or TRIS buffer after prereduction with L- cysteine resulted in the exclusive formation of the corresponding hydrides. Firstly, this phenomenon can endanger the accuracy of arsenic speciation which is based on hydride generation of substituted arsanes. Secondly, the more complex arsenic species can be converted to the hydride. That was demonstrated on hydride...
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UV-photochemical generation of volatile compounds of selenium and tellurium
Nováková, Eliška ; Hraníček, Jakub (advisor) ; Komárek, Josef (referee) ; Šíma, Jan (referee)
The presented thesis deals with UV-photochemical generation of volatile compounds of Se and Te from various species. The aim of the project was to expand the current state of knowledge by the application of photocatalytic reduction of higher oxidation states of Se and Te for the speciation analysis based on UV-photochemical generation of volatile compounds. The first step of the study was the assembly of the apparatus for the photocatalysed UV-photochemical generation of volatile compounds. The material of reactor and the whole experimental set-up were based on literature survey and previous research done in our research group. Experiments were directed towards finding the optimum conditions for generation of volatile compounds of selected model elements Se and Te. Se was studied as the element most commonly determined by the UV-photochemical generation of volatile compounds. Conversely, Te was selected as a model analyte representing elements forming less stable volatile compounds. The second part was the application of the optimised method of photocatalysed UV- photochemical generation of volatile Se compound to the determination of Se in water matrices, liquid certified reference materials and also samples of dietary supplements. TiO2/UV-photochemical generation was also successfully modified to...
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Optimization of generation and atomization of arsines for speciation analysis by atomic fluorescence spectrometry
Marschner, Karel ; Dědina, Jiří (advisor) ; Komárek, Josef (referee)
Speciation analysis of arsenic based on selective hydride generation and detection by atomic fluorescence spectrometry have been studied in this work. It was found that under optimum conditions of atomization in the flame in gas shield atomizer, sensitivity was approximately twice higher and detection limit was about four times lower compared to miniature diffusion flame, which is a standard atomizer for atomic fluorescence spectrometry. The conditions to generate hydrides from both inorganic forms of the arsenic, i.e. from arsenite and arsenate, with the same efficiency have been found in the batch arrangement, by using 1 mol dm-3 hydrochlorid acid and 1% solution of tetrahydridoborate. To determine only trivalent form, TRIS buffer at pH 6.00 was used together with 1% sodium tetrahydridoborate. The detection limits found for inorganic arsenic, i.e. for arsenite and arsenate, respectively, were 15 ng dm-3 and 9 ng dm-3 . It was found that in the batch arrangement under these conditions it is possible to generate corresponding hydrides methylarsonate and dimethylarsonate with the same efficiency as from the inorganic form. Finally, it was found when slightly changing the gas-liquid separator design in order to introduce the mixture of tetrahydridoborate with hydrochloric acid to the bottom of the...
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Selected inorganic pollutants in foodstuffs
Kroupová, Kateřina ; Vítová, Eva (referee) ; Vitoulová, Eva (advisor)
This bachelor thesis is focus on occurrence of inorganic pollutants in foodstuffs. The introduction is dedicated to apperance of individual selected elements in foodstuffs. Concentration of these elements is very important factor for examination of toxic effects for the human organism. If we want to avoid the harmful effects to the human organism, we have to define border limits. Work is based on the legislative of Czech republic. Second part of this study is focused on the biological monitoring. The biological monitoring is important for precautionary measures. In the third part of this study are described toxical effects of these elements to the human organism. Before qualitative and quantitative analysis by instrumental techniques is important to properly take the sample. In the fourth and fifth part of this work are mentioned methods used for determination of these elements and metods of taking samples. This bachelor thesis provide complex view on the problems of pollutants in foodstuffs and it should be used as a base for following diploma thesis.
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