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Photocatalysed Se Volatile Species Generation
Remperová, Natália ; Nováková, Eliška (advisor) ; Musil, Stanislav (referee)
Vapour generation techniques introduce the sample in the gas phase into the atomic absorption spectrometry detector. These generation techniques help to overcome the limitations of liquid sample introduction and allow to determine trace elements in different matrices. UV-photochemical generation is one of the techniques used for the generation of volatile species. Less harmful chemicals, minimisation of waste, more affordable analysis, or improved limits of detection are only a few benefits that this technique brings to the sample introduction techniques for spectrometric detectors in analytical chemistry. Selenium is one of the most studied elements by vapour generation techniques. However, a study of catalysed UV-photochemical generation of Se volatile species coupled with atomic absorption spectrometry detection and reliable determination of generation efficiency has not been published so far. The aim of this master project is to develop a method for the photochemical generation of Se volatile species from Se(IV) and Se(VI). Different photocatalysts are tested for the generation and their elemental composition, structure and size are investigated. First, the apparatus was assembled based on the information in the published literature and previous experiences of the researchers from our group....
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Possibilities of electrochemical generation of volatile compound of gold
Průša, Libor ; Hraníček, Jakub (advisor) ; Musil, Stanislav (referee)
The possibilities of electrochemical generation of gold volatile compound have been studied in this work. All experiments have been employed in electrochemical continuous flow generation. The previous aim of this work was to investigate if it is possible to generate the volatile form of gold using electrochemical generation of volatile compounds. Lead, platinum and alloy of lead and tin were used as cathode materials. Consequently, optimizations of experimental conditions were carried out. The optimized experimental conditions were: carrier gas flow rate, flow rate of electrolytes, electric current used for electrochemical generation, influence of the different types of gas-liquid separator, atomizer temperature. The calibration and other characteristics were found. At the conclusion, effect of oxygen on the signal intensity was studied. Key words Electrochemical generation of volatile compound atomic absorption spectrometry quartz tube atomizer flow-through electrolytic cell volatile compound gold
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Hydride generation of tellurium for atomic absorption spectrometry
Bufková, Kateřina ; Musil, Stanislav (advisor) ; Matoušek, Tomáš (referee)
This master's thesis deals with optimization of conditions of chemical hydride generation of tellurium and conditions of its atomization, specifically in three types of atomizers - in a diffusion flame (DF), in a heated multiple microflame quartz tube atomizer (MMQTA) and in a dielectric barrier discharge (DBD) atomizer. Tellurium hydride was generated in a flow injection arrangement and a high-resolution continuum source atomic absorption spectrometer was used for detection. As hydride generation can be only done from tetravalent species of tellurium, at first a simple procedure of pre-reduction of hexavalent species of tellurium by heating a standard in hydrochloric acid at 6 mol dm-3 was verified. Further, conditions of chemical generation were optimized with a goal to achieve as high generation efficiency as possible, namely, concentration of hydrochloric acid and sodium tetrahydroborate, volume of the reaction coil and a flow rate of carrier gas. Subsequently, conditions of atomization of tellurium hydride were examined with chosen optimal generation conditions. In the case of DF, it was an amount of hydrogen in the flame, a total flow rate of gases and observation height. In the case of MMQTA, temperature of the atomizer, a flow rate of carrier gas and a flow rate of air or oxygen needed for...
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Generation of volatile species of palladium for atomic absorption spectrometry
Vyhnanovský, Jaromír ; Musil, Stanislav (advisor) ; Matoušek, Tomáš (referee)
This thesis deals with optimization of the conditions for chemical generation of volatile species of palladium in combination with atomic absorption spectrometry. The volatile species of palladium were generated in a flow injection system by the reaction of an acidified sample with the solution of sodium borohydride in the presence of reaction modifiers. A diffusion flame atomizer was used due to its high robustness. In the first part of this thesis the optimization of parameters affecting the atomization in the diffusion flame was carried out (flow rates and composition of gases, observation height). In the second part, concentrations of individual reagents used (nitric acid, sodium borohydride, Triton X-100, Antifoam B, sodium diethyldithiocarbamate) were optimized. The positive effect of the reaction modifiers was demonstrated, especially that of sodium diethyldithiocarbamate, which lead to a tenfold increase in the sensitivity. The limits of detection and limits of quantification for the wavelength 244,8 nm were 0,25 mg dm-3 and 0,67 mg dm-3, respectively. The repeatability for this method for the concentration 5 mg dm-3 was 2,8 %. Key words: palladium, chemical generation of volatile species, atomic absorption spectrometry
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Photochemical vapor generation of rhenium with a detection by inductively coupled plasma mass spectrometry
Hašlová, Karolína ; Musil, Stanislav (advisor) ; Nováková, Eliška (referee)
This bachelor thesis deals with an optimization of the conditions of photochemical vapor generation of rhenium with detection by inductively coupled plasma mass spectrometry. Photochemical vapor generation was realized using an ultraviolet irradiation in a high-efficiency photochemical reactor with an inner reaction channel from a formic acid based medium in presence of reaction modifiers. Optimizations of parameters affecting the generation efficiency was implemented step by step - reaction medium flow rate (irradiation time), formic acid concentration, addition of acetic acid and reaction modifiers (transition metals) and carrier gas flow rate. The addition of an appropriate combination of reaction modifiers - cadmium(II) and iron(II) ions, had a key impact on photochemical generation of volatile species of Re and led to more than 40-fold increase in generation efficiency. A further (2-fold) increase in generation efficiency was achieved by wrapping the high-efficiency photochemical reactor with an aluminum foil, probably due to more efficient irradiation of the sample in the generator. The limit of detection and quantification were determined as 0.24 ng dm-3 and 0.80 ng dm-3 Re, respectively. The repeatability of the method 100 ng dm-3 Re was 4.8%. Key words photochemical vapor generation,...
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