National Repository of Grey Literature 149 records found  beginprevious56 - 65nextend  jump to record: Search took 0.00 seconds. 
Electrochemical generation of tellurium hydride for AAS
Resslerová, Tina ; Hraníček, Jakub (advisor) ; Červený, Václav (referee)
Tellurium is non-biological element which is not common in the earth. It can be accumulated in a body and cause many health problems. In this work, tellurium is determined by the electrochemical hydride generation technique coupled with atomic absorption spectrometry with quartz tube atomizer. In the first part of this work, various relevant parameters of tellurium hydride generation were optimized to achieve high sensitivity. Under the optimal working parameters, calibration dependences and other basic characteristics were measured. Finally, the influence of oxygen added on the different places of set up was carried out. Optimized parameters were flow rate of the carrier gas, generation current, flow rate and concentration of electrolytes. Optimizations were measured for two different catholytes: hydrochloric and sulfuric acid, with similar results. In addition the calibration was measured with orthophosporic acid. Further experiments with oxygen were performed for sulfuric acid as the catholyte. Influence of oxygen on the baseline and the process of determination were performed, for both continuous and limited time addition.
Examination of caesium concentration trends in extracts from cement blocks simulating radioactive waste
Straka, Marek ; Hraníček, Jakub (advisor) ; Nováková, Eliška (referee)
Cement is widely used as a solidification material of low and intermediate level radioactive waste containing caesium before shallow land burial. The aim of this thesis was to extract caesium out of 17 cement samples with 6 different cement binder compositions, by extraction with deionized water, then determine the amount of caesium in the extracts and look for trends in the extract Cs concentrations with various extraction duration. Cement samples, with stable caesium nuclide, were used to simulate retention of caesium in immobilized radioactive waste. Ten extractions from each sample in total were made with time ranging from 2 to 1032 hours. Atomic absorption spectrometry with flame atomization, using acetylene as fuel and air as oxidant, was used for caesium determination. This method was optimized and the addition of KCl serving as ionization buffer for better results was explored and compared. Keywords Atomic absorption spectrometry, flame atomization, caesium, extraction,
Determination of zinc, cadmium and nickel in leaves by inductively coupled plasma-mass spectrometry
Plodík, Michal ; Hraníček, Jakub (advisor) ; Červený, Václav (referee)
Práce je zaměřena na stanovení těžkých kovů (zinku, kadmia a niklu) v listech různých druhů stromů. Vzorky byly odebrány z různých lokalit na území České republiky. Pro analýzu byla použita hmotnostní spektrometrie s indukčně vázaným plazmatem, která je dostatečně citlivá pro předpokládané nízké koncentrace vybraných kovů. Pro stanovení koncentrace byla klíčová příprava vzorků pro mikrovlnný rozklad v koncentrované kyselině dusičné. Naměřené koncentrace sledovaných kovů se lišily nejen mezi lokalitami a jednotlivými rostlinnými druhy, ale také v rámci jedné lokality. Použitá metoda ICP-MS prokázala dostatečnou citlivost i u prvků s přirozeně nízkou koncentrací v životním prostředí, což bylo v této práci kadmium.
Chemiluminescent determination of vitamin B12 using sequential injection analysis
Doležalová, Veronika ; Hraníček, Jakub (advisor) ; Dian, Juraj (referee)
This bachelor thesis deals to find the optimal conditions for the determination of vitamin B12 by the Sequential Injection Analysis (SIA). The basis of the determination is a chemiluminescence reaction in which luminol is oxidized by hydrogen peroxide under the catalysis of cobalt ions in a basic medium. The intensity of the chemiluminescence radiation was measured using a spectrofluorometric detector and the measured intensities were recorded. Suitable experimental conditions were found experimentally before the actual determination. A total of 4 parameters were optimized, namely, the mass percentage of hydrogen peroxide, the ratio between the dosed cobalt ion sample and the luminol solution, the sample flow rate and the luminol concentration. Under optimized conditions, several solutions of known cobalt ion concentration were measured, from which a calibration dependence of chemiluminescence intensity on cobalt ion concentration could be established. For this determination, the basic characteristics were determined. For the determination of vitamin B12 itself by the SIA technique, it was assumed that the vitamin molecule contains exactly one cobalt atom, which was released from the molecule by the action of UV radiation. At the end of the work, the concentration obtained by the measurement was...
Development of a UHPLC-MS/MS method for determination of rivaroxaban in rat serum
Plášilová, Denisa ; Kozlík, Petr (advisor) ; Hraníček, Jakub (referee)
This bachelor thesis is focused on development of a specific UHPLC-MS/MS method for the determination of rivaroxaban in rat serum. At first, the setting of the mass spectrometer was optimized. Suitable MRM transitions were found for rivaroxaban and its isotopically labeled internal standard. For rivaroxaban was found the MRM transition 436.1 → 145.05 with optimal energy levels Q1 = -12.0 V; CE = -30.0 V; Q2 = -27.0 V. For rivaroxaban D4 was found the MRM transition 440.1 → 145.0 with optimal energy levels Q1 = -22.0 V; CE = -31.0 V; Q2 = -25.0 V. The ion source setting parameters were as follows: nebulizing gas flow 3 l/min; heating gas flow 10 l/min; interface temperature 300 řC; desolvation temperature 526 řC; DL temperature 250 řC; heat block temperature 400 řC; drying gas flow 10 l/min. The optimal chromatographic method was as follows: A Poroshell 120 SB AQ, 100 × 2.1 mm, 2.6 µm (Agilent) chromatographic column; the mobile phase consisted of acetonitrile with the addition of 0.1% formic acid (A) and distilled water with the addition of 0.1% formic acid (B); flow rate of the mobile phase 0.5 ml/min; gradient elution (time: 0-1-2-3.5-4-6.5 min; A: 20-20-80-80-20-20 % v/v); autosampler temperature 15 řC; column temperature 40 řC; time of analysis 6.5 minutes; injection volume 2 µl. The optimized...
Interferences in determination of antimony by UV-photochemical generation of volatile compounds and atomic fluorescence spectrometry
Kračmarová, Aneta ; Červený, Václav (advisor) ; Hraníček, Jakub (referee)
This work is focused on the study of interferents of selected elements during UV-photochemical generation of volatile antimony compounds. The interferents included transition metals, halides, hydride-forming elements and salts of mineral acids. Detection was performed by atomic fluorescence spectrometry. Some of the tested added substances proved to be potential reaction modifiers; in their presence, an increase in responses was observed. The best results were obtained using Fe3+ for the determination of Sb3+ and SO4 2- had the best results for the determination of Sb5+ . The largest interferent, i.e. the substance causing the most significant decrease in signal, was for both antimony ions Se4+ .
Determination of sodium and potassium in honey samples by atomic absorption spectrometry
Venclová, Veronika ; Hraníček, Jakub (advisor) ; Šíma, Jan (referee)
This bachelor thesis was focused on the determination of sodium and potassium in honey samples by atomic absorption spectrometry with a flame atomization technique. An acetylene-air flame was used. Prior to the analysis of the honey samples, the optimal working parameters of the used method were found. The optimized parameters were: the height of the beam above the burner, the flow rate of acetylene, and the burner's horizontal position. Under the optimal conditions, the basic characteristics of the determination of sodium and potassium were studied. Sodium and potassium concentrations in the honey samples were determined under optimal conditions. A total number of 27 honey samples were analyzed. The sodium content ranged from 0.880 to 25.3 mg/kg. The potassium content was in the range of 223 - 2750 mg/kg. In the end, the measured concentrations of honey samples originating from the Czech Republic were compared with the foreign studies. Keywords Potassium, sodium, honey, atomic absorption spectrometry, flame spectrometry
Determination of selected metals in tea samples and bag materials
Hlávka, Jan ; Nováková, Eliška (advisor) ; Hraníček, Jakub (referee)
This bachelor thesis is dealing with determination of antimony in materials modern pyramid-shape tea bags. Possible presence of antimony in these materials, e.g. polyethylene terephthalate (PET) or mixed materials, is caused by using it like catalyst in production of polyethylene terphthalete. The goal of this bachelor thesis is the verification of hypothesis, that antimony is present in materials of pyramide tea bags and that it is released to consumed drink, if higher concentration of antimony is present, and that it could pose a health risk to the consumer. At the same time, I studied if tea leaves are contaminated by other toxic elements, from which some can result from intesive agricultural production. They can be used as pesticides or be presnet in industrial fertilizers. In this thesis I examined the content of As, Cd, Cu, Sb and Zn in tea leaves sold in pyramide bags. These pyramide bags were purchased in local supermarkets and shops. The content of Sb in bags was determined too. The applied method included the decomposition of samples in a microwave decomposition device and analysis of the composition of the resulting solution by the ICP-MS method. Determined contents of the investigated elements were expressed like content of element in the sample in dry mass and the results were compared...
Determination of calcium, copper, and lead in leaves by inductively coupled plasma-mass spectrometry
Plecháč, Matěj ; Hraníček, Jakub (advisor) ; Červený, Václav (referee)
V této práci byly stanovovány koncentrace vápníku, mědi a olova ve vzorcích listů pomocí metody ICP-MS. Vzorkovaný materiál pocházel z různých míst České republiky a jednalo se o listy různých druhů stromů. Vzorky listů byly sušeny a poté rozloženy v mikrovlnném rozkladném zařízení za přítomnosti koncentrované kyseliny dusičné. Ve výsledcích bylo prokázáno, že koncentrace kovů se liší podle lokality sběru a v rámci jedné lokality byly různé u listů jednotlivých rostlinných druhů. Stanovené koncentrace vápníku se pohybovaly v rozmezí 5,6 - 30 mg/g a její průměrná koncentrace byla 14 mg/g. Koncentrace mědi byla v rozmezí 4,3 - 18 µg/g a její průměrná koncentrace byla 9,91 µg/g. Koncentrace olova byla v rozmezí 0,19 - 3,2 µg/g a jeho průměrná koncentrace byla 0,79 µg/g. V této práci bylo také ověřeno, že zvolený postup přípravy vzorků byl vhodný pro analýzu vzorků listů na ICP-MS, a že metoda ICP-MS byla díky nízkým limitům detekce vhodná pro stanovení koncentrací všech vybraných kovů.

National Repository of Grey Literature : 149 records found   beginprevious56 - 65nextend  jump to record:
Interested in being notified about new results for this query?
Subscribe to the RSS feed.