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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.
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Determination of Se in selected food supplements using electrochemical generation of H2Se and AAS
Králová, Pavlína ; Červený, Václav (advisor) ; Hraníček, Jakub (referee)
The aim of this bachelor thesis was to verify the efficiency of electrochemical generation of H2Se in connection with atomic absorption spectrometry used to determination of selenium in real samples, specifically in selected food supplements with the declared content of selenium. Firstly, working conditions of apparatus for electrochemical generation of H2Se with atomic absorption spectrometry were optimized. Using these optimized conditions, calibration dependences for SeIV a SeVI were measured. It was found that for the quantitative determination of selenate, the prereduction step is needed. Therefore, prereduction of SeVI to SeIV was also optimized. After prereduction step, new calibrations were measured and figures of merit of determination of these selenium species were achieved from them. In conclusion, concentrations of Se in real samples of selected food supplements with the declared contents of SeIV and SeVI were determined and interference effects for such determination have been discussed.
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Determination of Low Concentrations of Cationactive Tenzides in Water Samples using Flow Injection Analysis Technique with Spectrofluorimetric Detection
Havelka, Michal ; Rychlovský, Petr (advisor) ; Červený, Václav (referee)
This thesis was focused on a development of sensitive determination of cationactive tenzides by using the flow injection analyses with spectrofluorimetric detection. The determination was based on an interaction of cationactive tenzides with sodium salt of 4,5,6,7-tetrachloro-2',4',5',7'- tetraiodofluorescein dye (Bengal red) that generates a soluble associate in water environs. The sodium salt of 4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein is a fluorescence-active compound. A decrease of fluorescence intensity is detected as a result of the formation of fluorescence-inactive associate. A development of the determination proceeded in two steps. At first a static method of the determination was developed. Cetyltrimethylammonium bromide (CTAB) and N-(α-karbethoxypentadecyl)trimethyl ammonium bromide (Septonex) were used as a standard for cationactive tenzides. An optimal theoretical concentration of Bengal red dye (5.10-5 mol/l) was found, an optimum rate of pH for the fluorescence of Bengal red dye (pH = 9) was found, and a suitable kind of buffer for the environs of the interactions (25 mM phosphate buffer) was found. A linear dynamic range for the determination (Septonex) was in the interval: the limit of quantification - 7.10-5 mol/l. The limit of quantification was 3,72.10-6 mol/l. Next...
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Speciation analysis of selected mercury compounds using combined technique HPCL-EcMCVG-QFAAS
Leštinová, Veronika ; Červený, Václav (advisor) ; Spěváčková, Věra (referee)
Today, the information about total mercury content in a sample is not enough to know because of different toxicity of various species like inorganic forms such as Hg+ , Hg+II and organic bonded mercury in Methyl-mercury, Ethyl-mercury or Phenyl-mercury. Therefore a speciation analysis is needed to do. The aim of this diploma thesis was to develop and validate a new method for speciation determination of selected mercury compounds. This method comprises a connection of high performance liquid chromatography, electrochemical mercury cold vapor generation as a postcolumn derivatization technique and atomic absorption spectrometer. Using this on-line connection of mentioned techniques, an efficient separation of Hg+II and methylmercury was achieved. Reached limits of detection were 0.3 µgml-1 and 0.5 µgml-1 for Hg+II and methylmercury, respectively. At the end of experimental work, proposed hyphenated technique HPLC- EcMCVG-QFAAS was used for determination of these two mercury compounds in six real tap water samples (Bílý potok, Bílina, Labe, Vltava, Botič, pond Kovošrot). In Bílý potok, inorganic mercury (Hg+II ) was identified on the base of identical of retention time compared to standard. Standard addition method was used in both FIA and HPLC arrangements and determined content of Hg+II was (0.4...
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Tubular electrolytic cell for electrochemical generation of volatile compounds
Luštincová, Petra ; Hraníček, Jakub (advisor) ; Červený, Václav (referee)
The newly constructed tubular flow-through electrolytic cell useful for electrochemical generation of volatile compounds was used in this presented work. The general aim of this work was to test several cathode materials to obtain the best basic characteristics of selenium determination by electrochemical hydride generation using the tubular electrolytic cell. The tested cathode materials were lead wire, lead/tin alloy (75 % of Pb and 25 % of Sn) and granulated lead. At first the optimizations of relevant working parameters were carrier out for all of these cathode materials. Under the optimal working parameters, the basic characteristics of selenium determination were found. The highest sensitivity (7.6 · 103 dm3 µg-1 ) and the lowest limit of detection (0.42 µg.dm-3 ) were obtained for granulated lead as cathode material. Subject words: Analytical chemistry Key words: Atomic absorption spectrometry, electrochemical generation of volatile hydrides, tubular electrolytic cell
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The comparison of methods for determination of ascorbic acid in medical formulations
Kohoutová, Petra ; Nesměrák, Karel (advisor) ; Červený, Václav (referee)
The aim of this thesis is to compare and assess chosen analytical methods for ascorbic acid determination in pharmaceuticals with respect to their correctness, accuracy, time and finance exigencies. Four methods were chosen alkalimetric titration with visual and instrumental indication, iodometry and spectrophotometry. Pills, capsules and injection solution were chosen as samples of pharmaceuticals. The obtained results as to accuracy of the declared value (or range permitted under Pharmacopoeia) agreed by all titration methods, spectrophotometric determination showed overestimated results. All used methods were approximately equally accurate. As time seems to be most optimal acidobasic titration with visual indication, while demanding in terms of time was spectrophotometry. If we consider methods on financial intensity all titration methods were quite equal.
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Possibilities of electrochemical generation of volatile compound of silver
Linhart, Ondřej ; Hraníček, Jakub (advisor) ; Červený, Václav (referee)
The presented bachelor thesis is to focus on the possibilities of electrochemical generation of volatile form of silver coupled with atomic absorption spectrometry which was used as a detection technique. The main aim was to optimize working parameters. A thin-layer electrolytic cell and a tubular electrolytic cell have been tested for the electrochemical generation of volatile form of silver. The optimization of appropriate electrolyte, its concentration and its flow rate, electric current and flow rate of carrier gas have been developed. Under the optimal working conditions the sensitivity of 0.029 dm mg-1 for the determination of silver by electrochemical generation was achieved.
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The Speciation Analysis of the Toxicological Important Forms of the Arsenic in Urban Particulate Matter Samples with the Detection QF-AAS
Jelínek, Petr ; Rychlovský, Petr (advisor) ; Červený, Václav (referee)
The topic of this diploma thesis was the speciation analysis of the toxicological important forms of the arsenic in urban particulate matter samples. The detection technique used in this work was atomic absorption spectrometry with quartz atomizer. Acetic acid, ammonium acetate, hydroxylamine, potassium hydroxide and sodium carbonate are recommended leaching agents for extraction of metals from urban particulate matter samples. Results of the presenting work are following: Acidic extraction reagents can be not recommended for the speciation analysis of the arsenic, because these reagents lower sensitivity of the determination of As3+ and As5+ too and destroy the quartz atomizer. Alkaline extraction reagents don't lower sensitivity of the determination of As3+ and these reagents don't destroy the atomizer, but lower sensitivity of the determination of As5+ was obtained. Recommended reagents aren't useful for extraction of the metals from urban particulate matter samples for the speciation analysis.
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