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Hydride generation study for arsenic speciation analysis with AAS and AFS detection
Svoboda, Milan
The general aim of this work was a development of methodology and instrumentation for speciation analysis based on the combination of the selective generation of substituted hydrides with atomic absorption or atomic fluorescence spectrometry detection. The first topic of this work was the development of methodology and instrumentation for arsenic speciation analysis based on selective generation of substituted arsines with trapping in the cryogenic trap (U-tube packed with chromosorb) with AAS detection (HG- CT-AAS). The conditions of the selective hydride generation approach as well as working procedure of the cryogenic trap were optimized (appropriate approach for hydride generation, set up of heating program of cryogenic trap, new dryer - cartidge with NaOH, elimination of unspecific absorption, decreasing of the detection limits). The second important part of the work lay in applying of the developed method for arsenic speciation analysis in a homogenized mouse liver tissue. The direct slurry sampling to hydride generator was develop. Moreover the information about oxidation state (iAsIII,V , MAsIII,V a DMAsIII,V ) was obtain. The effect of relevant experimental parameters such as tetrahydroborate concentration, TRIS buffer concentration and time of pre-reduction of the samples by L-cysteine...
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Interference study by selenium determination using UV-photochemical generation of its volatile species in formic acid media with AAS detection
Duben, Ondřej ; Červený, Václav (advisor) ; Kratzer, Jan (referee)
The aim of this work was to experimentally observe the impact of various potential interferents on the determination of selenium using UV-photochemical generation of its volatile species in formic acid media with AAS detection. HNO3, As3+ , Co2+ , Cu2+ and Ni2+ were chosen as model substances affecting the analyte response. All these substances were found significant interferents. Some of these substances (HNO3, As3+ , Cu2+ , Ni2+ ) increased the signal at low concentration, but the signal of selenium decreased significantly at their higher concetration in a sample. Inverse shape of the dependence of the analyte response on the interferent concentration was observed for Co2+ ions. It was found that the reagent Chelaton II, often used in analytical chemistry to mask interferents, also caused a suppression of selenium signal. On the contrary, other maskig agents tested (triethanolamine, amonnium formate) did not lead to any interference. Key words: selenium, UV- photochemical generation of volatile compounds, formic acid, AAS, interference, masking
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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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Speciation analysis of toxicologocally important forms of arsenic: development and comparison of hydride generation based methods with ICP-MS detection
Trojánková, Nikola ; Matoušek, Tomáš (advisor) ; Száková, Jiřina (referee)
Nowadays, arsenic is becoming an important pollutant in the environment. Chronic exposure to arsenic can cause number of serious diseases. Therefore, a development of analytical methods for trace and ultratrace speciation analysis- analysis of individual forms or phases in which As is found in the sample - is fully in place. This Thesis compares four methods of trace speciation analysis, with focus on limits of detection and quantification, and on comparison of results of analysis of river and sea water reference materials. Methods based on hydride generation with preconcentration by cryotrapping and AAS or ICP-MS detection, with limits of detection in ng or tenths of ng·dm-3 , are compared with procedures employing HPLC, with ICP-MS detection. The Thesis includes development and optimization of a pre-reduction step of postcolumn hydride generation with on-line pre-reduction of pentavalent arsenic species, in order to improve sensitivity of this method. Limits of detection around 10 ng·dm-3 are achieved. The results of analyses obtained by individual methods are in excellent agreement. Keywords: Arsenic, speciation analysis, hydride generation, atomic absorption spectrometry, inductively coupled plasma- mass spectrometry, high efficiency liquid chromatography, limits of detection.
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The use of ion exchanges for preconcentration of platinum group metals
Sýkora, Jiří ; Řezáčová, Veronika (referee) ; Komendová, Renata (advisor)
The aim of this thesis is the elaboration of a detailed literature review on the use of ion exchangers for the preconcentration of platinum group metals. This work contains an actual literature review on this issue. In this work you will find information about the current occurrence of platinum metals in the environment, their impact on health, properties, resources and the use. There are also described ways of decomposition, extraction and use of ion exchangers. In the experimental part this thesis deals with optimization of ion exchangers and following application of real samples from the city of Brno.
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Increasing of the efficiency of electrochemical generation of volatile form of cadmium for trace analysis using AAS
Růžková, Pavla ; Rychlovský, Petr (advisor) ; Červený, Václav (referee)
The aim of the diploma thesis was an improvement of the efficiency of electrochemical generation of volatile form of cadmium used in atomic spectrometric methods. The increase of the efficiency of electrochemical generation of volatile form results in overall improvement of the sensitivity of measurement and therefore, it is possible to achieve lower values of detection limits and limits of determination. One of all the possibilities for improving of overall efficiency is a minimization of loss of volatile form of Cd during transport. Another essential possibility is coupling of the technique of electrochemical generation of volatile form of Cd with in-situ collection (and atomization) in graphite furnace of atomic absorption spectrometer. Keywords: Atomic absorption spectrometry, electrochemical generation of volatile compounds, generation efficiency, electrolytic flow-through generation cell, quartz-tube atomizer, graphite furnace, in-situ trapping, cadmium
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Platinum group elements in waste and surface waters
Novotný, Matěj ; Řezáčová, Veronika (referee) ; Komendová, Renata (advisor)
This assignment provides a detailed description of platinum metals, their occurrence in surface and waste water and their determination options. Currently, platinum metals are widely used in the automotive industry as a part of a catalyst, as well as in medicine and jewelery. Release of these metals in pure form and the form of oxides leads to their subsequent accumulation, which directly affects fauna and flora. Due to that, the living conditions and health status of some organisms are petting worse.
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Microdetermination of cobalt by methods of molecular and atomic absorption spectrometry
Charuza, Martin ; Řezáčová, Veronika (referee) ; Sommer, Lumír (advisor)
This diploma thesis is focused on microdetermination of cobalt by UV-VIS spectrophotometry with organic agents and comparison with atomic absorption spectrometry. In the first part properties, occurance and importance of cobalt in the environment are desribed, complete with as a part of vitamine B12. Attention is also given to cobalt compounds, especially in the oxidative states +II and +III. Methods of preconcentration and preparation cobalt determination in real samples are adduced. In this thesis are described some optical analytical methods with accept on spectrophotometric agents for determination of cobalt. The experimental part of this thesis icludes optimalization of the spectrophotometric determination of cobalt with choosen organic agents 4-(2-pyridylazo)resorcin and 2-(5-Brom-2-pyridylazo)-5-diethylaminophenol and optimalization of atomic absorption spectrometry for cobalt determination. All of real samples of water (surface, underground, mineral and waste) were measured by both 4-(2-pyridylazo)resorcin and 2-(5-Brom-2-pyridylazo)-5-diethylaminophenol via UV-VIS and via atomic absorption spectrometry. Results of determinations were compared. A sample of vitamine B12 was measured too by all techniques.
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Bioavailability of metals species in water ecosystem
Tandler, Ágnes ; Řezáčová, Veronika (referee) ; Vávrová, Milada (advisor)
Koncentrace volných kovových iontů je často jen malou částí celkové koncentrace kovu v prostředí. Přes tento malý obsah, je ve většině případů koncentrace volných kovových iontů klíčovým faktorem při určování biodostupnosti a toxicity pro organizmus. Membránová technika Donnan se používá k měření koncentrace volných kovových iontů a v této diplomové práci je ověřena pro směsi kovů (Pb + Cu) při absenci a přítomnosti malých organických ligandů. Olovo a měď jsou environmentálně důležité kovy díky své toxicitě a rozdílným vazebným vlastnostem ve vztahu ke studovaným ligandům.
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