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Selenium determination by HG-AAS with preconcentration and atomization in a dielectric barrier plasma discharge
Duben, Ondřej ; Kratzer, Jan (advisor) ; Rychlovský, Petr (referee)
The aim of this thesis was to optimize atomization conditions for selenium hydride in a novel plasma atomizer based on dielectric barrier discharge (DBD) using atomic absorption spectrometry as a detector. Analytical characteristics have been subsequently determined and compared to those reached in a conventional externally heated quartz tube atomizer which was replaced by a sofisticated design of a multiatomizer (MMQTA) in this work. The limit of detection reached in DBD (0,24 ng ml−1 Se) is slightly worse to that observed in MMQTA (0,15 ng ml−1 Se). On the contrary, slightly better resistance towards interferences of Sb, Bi and As was observed in DBD atomizer in comparison with MMQTA. Possibility of selenium preconcentration in a DBD atomizer was studied reaching an overall preconcentration efficiency of 75 ± 5%. The detection limit in a preconcentration mode employing preconcentration period of 300 s has reached 0,012 ng ml−1 Se. Key words: hydride generation atomic absorption spectrometry, dielectric barrier discharge, hydride atomization, hydride trapping, selenium
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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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