National Repository of Grey Literature 70 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
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...
Miniature plasma DBD atomizer for AAS and AFS
Straka, Marek ; Kratzer, Jan (advisor) ; Hrdlička, Aleš (referee)
Five designs of dielectric barrier discharge (DBD) atomizers have been constructed and optimized employing arsane as a model analyte. The individual DBD designs differed from each other in the style of electrode attachment, electrode shape and area. An externally heated quartz tube atomizer and another DBD atomizer design that have been studied before were used as reference. All the atomizer designs studied including the reference atomizers were found compatible with detection by atomic absorption spectrometry (AAS) giving comparable sensitivity of 0.44 s ng-1 As and detection limit around 0.2 ng ml-1 As under optimum atomization conditions. However, significant differences in optimum operation conditions were found among the DBD designs in terms of the applied voltage depending strongly on the style of electrode attachment. The design with metal strip electrodes glued to a quartz body requires more than 14 kV to be operated. The design with sputtered electrodes of the same shape can reach the same sensitivity with 8.5 kV. Selected DBD designs have been proven to be compatible also with other spectrometric detectors such as atomic fluorescence spectrometry (AFS) reaching detection limit 0.05 ng ml-1 As or atomic emission spectrometry (AES) with detection limit of 30 ng ml-1 As showing the...
Analysis of selected elements in dendrological sample of spruce trunk
Pastrňáková, Aneta ; Hraníček, Jakub (advisor) ; Šíma, Jan (referee)
The aim of this bachelor thesis was to determine selected elements, specifically iron, manganese, sodium, potassium, calcium, magnesium, barium, copper, zinc, strontium and aluminium in the sample of a spruce wood, taken from a dry tree from an area of South Bohemia. As a suitable and sufficiently sensitive method an atomic absorption spectrometry with flame atomization was used in this bachelor thesis. Before the analysis optimal conditions for the determination of these elements were experimentally found. The beam height above the burner edge and the acetylene flow rate were optimized depending on the type of oxidant used. Under the optimal conditions, the basic characteristics of the determination of individual elements were determined. These characteristics include mainly the limit of detection and quantification, sensitivity and repeatability. Optimized methods for determination of the selected elements were further applied for the analysis of real spruce wood samples. These samples were prepared by decomposition of the wood in a microwave device in the presence of nitric acid. In order to suppress interference, the suitable reagents were added to the analyzed samples to determine the selected elements (sodium, potassium, magnesium, calcium, barium). In total, 22 samples of wood of different...
Photochemical generation of volatile species of cobalt for analytical atomic spectrometry
Vyhnanovský, Jaromír ; Musil, Stanislav (advisor) ; Nováková, Eliška (referee)
This master's thesis deals with the optimization of conditions for photochemical generation of volatile species of cobalt. Volatile species of cobalt were generated in a flow injection system using a high-efficiency flow through UV generator from formic acid based medium. For detection a high-resolution continuum source atomic absorption spectrometer was used. The volatile species were atomized using a diffusion flame atomizer because of its high robustness. First the optimizations of the parameters affecting the atomization in the diffusion flame and the parameters affecting the transport of the volatile species from the UV generator into the atomizer were carried out (flow rates and composition of the gases, type of a separator, observation height). After that, the optimization of the parameters of the photochemical generation itself was carried out. These were the composition of a reaction medium (concentration of formic acid and formate, type of formate salt) and irradiation time. The possibility of generation of the volatile species from acetic acid based medium was also investigated, but no signal was observed. At chosen optimal conditions of generation the influence of potential interferents was examined, mainly from inorganic acids (HNO3 and HCl) and some transition metals (Fe, Cu and Ni)....
Removal of lead from wastewater using a constructed wetland
Removal of lead from municipal wastewater using a constructed wetland with a horizontal subsurface flow was studied. Wastewater, wetland plant and sediment samples were analyzed using an AAS Thermo Scientific iCE 3500. Average concentrations of lead in inflow and outflow water in 2015 were 1.47 and 0.74 ?g/l, respectively. Average concentrations of lead in inflow and outflow water in 2016 were 0.75 and 0.38 ?g/l. The average efficiency of lead removal was 49.2 %. Lead concentrations in vegetation (Phragmites australis) varied in the range of 0.081-0.087 mg/kg and 0.48-0.17 mg/kg for the above and belowground biomass, respectively. Lead concentration in sediments were 9.79 and 4.86 mg/kg at distances of 1 and 10 m from inflow zone. Lead and other heavy metals were predominantly removed from wastewater at the initial part of the wetland bed.
Comparison of selenium extraction efficiency from food supplements
Molnárová, Lucia ; Hraníček, Jakub (advisor) ; Červený, Václav (referee)
The aim of this bachelor thesis was comparison of selenium extraction efficiency from food supplements which contain various declared forms of selenium. The method of atomic absorption spectrometry with flame atomization was used to determine the efficiency of the extraction. The first step for the determination of selenium in four real samples was the experimental finding of optimal conditions for selenium determination by flame AAS technique. Optimized parameters included the flame composition, the fuel flow rate, the angle of burner rotation, the horizontal burner position and the spectral range. During the testing the flame composition, higher responses were measured by using air as an oxidant, and therefore acetylene-air flame was used to other optimize and measure real samples. After optimization of the conditions, the calibration dependence was determined and the basic characteristics of the measurements were calculated. The detection limit and determination repeatability, sensitivity and operating range were determined for selenium determination. The detection limit was 0.12 mg dm-3 . The real samples of the food supplement tablets were mechanically homogenized and transferred to aqueous solutions, which were subsequently analyzed by the optimal conditions. The highest extraction efficiency...
Optimization of atomization conditions for bismut, lead and tellurium hydrides for development of hydride atomizers.
Štádlerová, Barbora ; Hraníček, Jakub (advisor) ; Spěváčková, Věra (referee)
This Master thesis is a part of a project: Hydride atomizers for atomic absorption and atomic fluorescence spectrometry - new horizons (GA ČR, P206/17-04329S, principal investigator: prof. RNDr. Jiří Dědina, CSc. DSc.) of which the general target is to make a leap towards the ideal hydride atomizer by optimization of atomization based on the knowledge of the distribution of free atoms and hydrogen radicals inside the atomizers. This thesis contributes to the project by optimizing the atomization parameters for atomic absorption spectrometry with hydride generation. The atomization parameters were optimized for three different types of atomizers - multiatomizer, diffusion flame and "flame-in-gas-shield" atomizer using three different analytes - bismuth, lead and tin. Optimal atomization parameters were found for each of the atomizer and each of the analyte - carrier gas flow and flow of other gases if needed for the analysis. Calibration curves and analytical figures of merit such as sensitivity, LOD and LOQ were estimated. Final comparison is based on the data obtained from calibration curves. MDF and FIGS atomizers are mostly used with AFS detection and they provide lower sensitivity and higher detection limits with AAS detection in comparison with MMQTA. Since the analytes are known to trap...
Analysis of nanopartical systems by atomic spectrometry
Jeníková, Eva ; Hraníček, Jakub (advisor) ; Nováková, Eliška (referee)
EN The present diploma thesis is focused on optimization methods of titanium and phosphorus concentration for their use in the colloidal solution of TiO2 nanoparticles modified by bisphosphonates. For these analyses was used atomic absorption spectrometry with flame and electrothermal atomization. The characteristics of the two analytes were compared to two different spectrometers. Using the F-AAS technique on the GBC 933 AA spectrometer has been achieved a detection limit of 5,2 mg l-1 for titanium and a detection limit of 163 mg l-1 for the phosphorus. Using the ContrAA 700 spectrometer, F-AAS has been achieved an almost five times lower detection limit of 1,1 mg l-1 for titanium determination. For determination of phosphorus using this spectrometer, was obtained a similar value of 151 mg l-1 , as using the GBC 933 AA spectrometer. The determination of phosphorus by the ET-AAS technique using the ContrAA 700 spectrometer resulted in a detection limit of 1,23 mg l-1 , which is a significant difference compared to the flame system. It has been proved that optimized methods are consistent with the intention, which was confirmed by the analysis of real titanium and phosphorus samples in the colloidal solution of TiO2 nanoparticles modified bisphosphonates.
Arsenic speciation analysis by hydride generation - cryotrapping - gas chromatography - atomic absorption spectrometry
Petreňová, Štěpánka ; Svoboda, Milan (advisor) ; Šucmanová, Marcela (referee)
EN The thesis is focused on a speciation analysis of arsenic with use of the hydride generation - cryotrapping - gas chromatography - atomic absorption spectrometry. The aim of this project was the development of a method and instrumentation of the speciation analysis of arsenic based on combination of selective generation of substituted hydrides with a detection by atomic absorption spectrometry and with use of the cryotrapping of generated arsenic species and their separation by the gas chromatography. In the first part of this work the effects of individual parameters which influence the separation in the gas chromatograph were studied. Especially, time of injection from the cryotrap into GC, temperature program, carrier gas flow and carrier gas flow through a "deanswitch". Optimization of these parameters is an attempt to achieve a satisfactory resolution of the individual peaks of arsenic species separated by gas chromatography. Furthermore, an adequate sensitivity of this method is required to be achieved in comparison to other methods that use AAS detection such as a combination of hydride generation with cryotrapping. For this reason, the detection limits and the quantification of arsenic species were important to be determined as well. A sampling coil was replaced by a sampling tip...
Method Development for Speciation Analysis of Volatile Mercury Forms in Ambient Air and flue Gases from Incineration Plants.
Švehla, Jaroslav ; Kratzer, J. ; Svoboda, M. ; Svoboda, Karel ; Šyc, Michal ; Ružovič, Tomáš
Potential of AAS for on-line speciation analysis of gaseous Hg0 (non-heated atomizer) and HgCl2 (heated atomizer) in flue gases is discussed.
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