|
|
UV-photochemical generation of volatile compounds of selenium and tellurium
Nováková, Eliška
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...
|
|
|
Speciation analysis of arsenic and mercury using postcolumn generation of their volatile compounds for needs of atomic spectroscopic methods
Linhart, Ondřej
The presented dissertation thesis deals with the use of UV-photochemical generation of volatile compounds (UV-PVG) as a derivatization technique for the combination of high-performance liquid chromatography (HPLC) and atomic absorption spectrometry (AAS) detection. Two model elements arsenic and mercury and their compounds were selected for the speciation analysis. The work was divided into several parts that follow. In the first part of the research, the apparatus for the UV-photochemical generation of the volatile mercury compounds and their detection with a new continuum source and high-resolution atomic absorption spectrometer (HR-CS AAS) with an externally heated detection tube was constructed. The analytical method was adapted for use with atomic fluorescence detection with the aim to improve sensitivity of the determination. Furthermore, apparatus for the electrochemical generation of cold mercury vapor with AAS detection was built. The construction of the apparatus was followed by optimization of the reaction conditions (concentration and flow of electrochemical reagents: sulfuric and hydrochloric acid, mobile phase, carrier medium, flow rate of the carrier gas and localization of its introduction), determination of the analytical figures of merit, and comparation of the methods. Both...
|
|
|
Chemical generation of volatile mercury species for speciation analysis - method optimization and analytical applications
Migašová, Michaela ; Petry-Podgórska, Inga (advisor) ; Spěváčková, Věra (referee)
Experimental conditions have been optimized for volatile species generation (VSG) of four mercury species and their subsequent atomization with detection by atomic absorption spectrometry (AAS). The species investigated were mercury (+II), methylmercury (+I), ethylmercury (+I) and phenylmercury (+I). Flow injection construction of volatile species generator and externally heated quartz tube atomizer were employed. The optimized parameters were the concentration of hydrochloric acid and sodium borohydride, the length of the reaction coil, carrier gas flow rate, atomization temperature and the amount of oxygen present in the atomizer. Furthermore, the effect of the drying tube on the signal of Hg species as well as the applicability of tin chloride as an alternative reductant instead of sodium borohydride were studied. Calibration curves were measured and the basic analytical figures of merit were determined, under optimum experimental conditions, for all four mercury species investigated. Limits of detection for Hg species ranged from 0.12 to 0.25 ng cm-3 , while sensitivity reached ca 0.10 s ng-1 at atomization temperature of 500 řC. Experiments focused on atomization temperature optimization have revealed that volatile compounds generated from organic Hg species decompose significantly. Speciation...
|
|
|
Analysis of unstable complexes for study of enzymatic methylation of arsenic
Albrecht, Michal ; Petry-Podgórska, Inga (advisor) ; Červený, Václav (referee)
The main aim of this thesis was the development of conjugation of existing methods for analysis of arsenic-glutathione complexes (As-GS complexes) together with simple arsenic species (iAs, MMAs, DMAs) during simple run. The basic technique for analysis of As-GS complexes was the HPLC-ICP-MS method with a reverse phase separation column (C18). The separation problem of simple species has been overcome by extending of system by postcolumn hydride generation with cryotrapping system (HG-CT). The resulting HPLC/HG-CT-ICP-MS system provides a complex analysis of all the above-mentioned analytes. According to the currently available resources, it is an innovative system, where for the first time all the simple arsenic species (iAs, MMAs, DMAs) and the As-GS complexes were separated. Under the given conditions, the detection limit for the As-GS complexes of 1.9 pg cm-3 in the RP-HPLC-ICP-MS system (a quantification limit of 6.5 pg cm-3 ) was achieved at a sensitivity of 468 CPS s pg-1 . The HG-CT-ICP-MS system provided a detection limit for iAs of 1.2 pg cm-3 at a sensitivity of 1121 CPS s pg-1 , for MMAs of 0.043 pg cm-3 at a sensitivity of 895 CPS s pg-1 and for DMAs of 0.076 pg.cm-3 at a sensitivity of 926 CPS s pg-1 . This method was applied to achieve another aim, studying the pathways of enzymatic...
|
|
|
Speciation analysis of mercury in liquid and gaseous samples
Žídek, Radek ; Kratzer, Jan (advisor) ; Spěváčková, Věra (referee)
Generation efficiency of four mercury species, namely elemental mercury and hydrides of methyl-, ethyl- and phenylmercury from liquid samples was quantified. The species chemically generated were quantitatively trapped on a gold-coated amalgamator to be subsequently determined by AMA-254 technique. Three types of construction of volatile species generators were compared. Generation effciciency among the species was comparable, fluctuating around 60% in the conventional flow injection generator equipped with a gas liquid separator with forced outlet. Better results were reached for elemental mercury and methylmercury hydride in an automated batch generator system. Generation efficiency was higher than 90% for these two species and between 60 to 80% for ethyl- and phenylmercury hydrides, respectively. Speciation analysis of elemental mercury and sublimate in gaseous samples was optimized. These two species dominate in flue gases produced during coal combustion or waste incineration. Combination of two sorbent tubes packed with alumina and gold-coated alumina enables selective and quantitative retention of both species. Sublimate is trapped on a column packed with alumina while elemental mercury is retained on gold-coated alumina. The capacity of both sorbents was investigated as well as the effect of...
|
|
|
Speciation analysis of arsenic and mercury using postcolumn generation of their volatile compounds for needs of atomic spectroscopic methods
Linhart, Ondřej
The presented dissertation thesis deals with the use of UV-photochemical generation of volatile compounds (UV-PVG) as a derivatization technique for the combination of high-performance liquid chromatography (HPLC) and atomic absorption spectrometry (AAS) detection. Two model elements arsenic and mercury and their compounds were selected for the speciation analysis. The work was divided into several parts that follow. In the first part of the research, the apparatus for the UV-photochemical generation of the volatile mercury compounds and their detection with a new continuum source and high-resolution atomic absorption spectrometer (HR-CS AAS) with an externally heated detection tube was constructed. The analytical method was adapted for use with atomic fluorescence detection with the aim to improve sensitivity of the determination. Furthermore, apparatus for the electrochemical generation of cold mercury vapor with AAS detection was built. The construction of the apparatus was followed by optimization of the reaction conditions (concentration and flow of electrochemical reagents: sulfuric and hydrochloric acid, mobile phase, carrier medium, flow rate of the carrier gas and localization of its introduction), determination of the analytical figures of merit, and comparation of the methods. Both...
|
|
|
UV-photochemical generation of volatile compounds of selenium and tellurium
Nováková, Eliška
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...
|
|
|
Speciation analysis of arsenic and mercury using postcolumn generation of their volatile compounds for needs of atomic spectroscopic methods
Linhart, Ondřej ; Červený, Václav (advisor) ; Spěváčková, Věra (referee) ; Šíma, Jan (referee)
The presented dissertation thesis deals with the use of UV-photochemical generation of volatile compounds (UV-PVG) as a derivatization technique for the combination of high-performance liquid chromatography (HPLC) and atomic absorption spectrometry (AAS) detection. Two model elements arsenic and mercury and their compounds were selected for the speciation analysis. The work was divided into several parts that follow. In the first part of the research, the apparatus for the UV-photochemical generation of the volatile mercury compounds and their detection with a new continuum source and high-resolution atomic absorption spectrometer (HR-CS AAS) with an externally heated detection tube was constructed. The analytical method was adapted for use with atomic fluorescence detection with the aim to improve sensitivity of the determination. Furthermore, apparatus for the electrochemical generation of cold mercury vapor with AAS detection was built. The construction of the apparatus was followed by optimization of the reaction conditions (concentration and flow of electrochemical reagents: sulfuric and hydrochloric acid, mobile phase, carrier medium, flow rate of the carrier gas and localization of its introduction), determination of the analytical figures of merit, and comparation of the methods. Both...
|
|
|
Determination of arsenic species in seafood reference materials by ICP-MS with hydride generation and cryotrapping
Pokorná, Nikola ; Matoušek, Tomáš (advisor) ; Červený, Václav (referee)
The aim of this work was to determine chemical species of arsenic in sea originating certified reference materials. Measurements were done using method of hydride generation. Hydrides were preconcentrated in liquid nitrogen cooled tube and detected using inductively coupled plasma mass spectrometry. During the testing of the method, mutual conversion of arsenic species was observed for inorganic arsenic, monomethyl arsenic and dimethylarsenic. Further study revealed that with presence of matrix and hydrogen peroxide, demethylation occured only in hydride generation phase, not during extraction. Dissociation of hydrogen peroxide in extracts was verified using catalase. End of the demethylation process was proved using measurement with addition of arsenic species standards. The newly invented procedure was used to determine arsenic species in reference materials with sufficient accuracy. Final results are compatible with results from different method, and already published results as well. Key words: speciation analysis, arsenic, hydride generation, seafood, inductively coupled plasma mass spectrometry
|
|
|
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...
|
guest ::
