National Repository of Grey Literature 8 records found  Search took 0.00 seconds. 
Optimization of chemical generation and subsequent atomization of volatile cadmium species for atomic absorption spectrometry
Sagapova, Linda ; Kratzer, Jan (advisor) ; Marschner, Karel (referee)
Generation and atomization of cadmium volatile compounds was optimized in this work in order to determine trace Cd concentration levels by volatile compound generation (VCG) with subsequent detection by atomic absorption spectrometry (AAS). Three designs of volatile compound generators have been tested including a conventional hydride generator in flow injection analysis (FIA) mode, a batch generator as well as a generator of volatile compounds of transition metals. The generation efficiency of Cd species was quantified as low as 4 % in the conventional hydride generator. Providing that dissolved oxygen was removed from the reaction solutions, the generation efficiency of Cd increased to 12 % in the same experimental arrangement. The highest Cd generation efficiency of 54 % was reached in the generator of volatile compounds of transition metals. In this set up a detection limit of 0.07 ng ml-1 Cd and a sensitivity of 3.2 s ng-1 Cd, respectively, were reached. Moreover, the structure of the volatile Cd species generated was identified as free atoms in all experimental arrangements of the generators investigated. Keywords atomic absorption spectrometry, cadmium, generation of volatile compounds, atomization of volatile compounds
Development of Instrumentation and Methodology for Elemental and Speciation Analysis of Arsenic Based on Hydride Generation and on Atomic Fluorescence Spectrometric Detection
Marschner, Karel ; Dědina, Jiří (advisor) ; Kanický, Viktor (referee) ; Spěváčková, Věra (referee)
(EN) The presented dissertation is devoted to hydride generation from arsenic species and its application for speciation analysis based on atomic fluorescence detection. Hydride generation from toxicologically relevant arsenic species was optimized in order to achieve a 100% efficiency. The resulted experimental setup was subsequently used for speciation analysis of arsenic in human urine by high performance liquid chromatography with detection by atomic fluorescence spectrometry. The accuracy of the developed method was verified by comparative analyses of human urine samples collected from five individuals with an independent reference method. The cleavage of As-C bond during the reaction of methylated arsenic species with tetrahydridoborate(1-) (THB) in acidic media was studied in detail. Pronounced demethylation of methylated arsenic species was found during the reaction of THB with HCl, H2SO4, and HClO4 while hydride generation from CH3COOH or TRIS buffer after prereduction with L- cysteine resulted in the exclusive formation of the corresponding hydrides. Firstly, this phenomenon can endanger the accuracy of arsenic speciation which is based on hydride generation of substituted arsanes. Secondly, the more complex arsenic species can be converted to the hydride. That was demonstrated on hydride...
Determination of Inorganic Arsenic in Samples of Marine Origin
Marschner, Karel ; Matoušek, Tomáš ; Dědina, Jiří ; Musil, Stanislav
A fast screening method for determination of inorganic arsenic in marine samples was developed. This method is based on selective\nhydride generationanddetectionby inductively coupled plasmamass spectrometry. Using a high concentration of hydrochloric acid\ntogether with hydrogen peroxide for hydride generation leads to selective conversion of inorganic arsenic species into arsane. The\naccuracy of this method was verified by comparative analyse by high performance liquid chromatography coupled with hydride generationandatomic\nfluorescence detection.
Optimization of generation and atomization of arsines for speciation analysis by atomic fluorescence spectrometry
Marschner, Karel ; Dědina, Jiří (advisor) ; Komárek, Josef (referee)
Speciation analysis of arsenic based on selective hydride generation and detection by atomic fluorescence spectrometry have been studied in this work. It was found that under optimum conditions of atomization in the flame in gas shield atomizer, sensitivity was approximately twice higher and detection limit was about four times lower compared to miniature diffusion flame, which is a standard atomizer for atomic fluorescence spectrometry. The conditions to generate hydrides from both inorganic forms of the arsenic, i.e. from arsenite and arsenate, with the same efficiency have been found in the batch arrangement, by using 1 mol dm-3 hydrochlorid acid and 1% solution of tetrahydridoborate. To determine only trivalent form, TRIS buffer at pH 6.00 was used together with 1% sodium tetrahydridoborate. The detection limits found for inorganic arsenic, i.e. for arsenite and arsenate, respectively, were 15 ng dm-3 and 9 ng dm-3 . It was found that in the batch arrangement under these conditions it is possible to generate corresponding hydrides methylarsonate and dimethylarsonate with the same efficiency as from the inorganic form. Finally, it was found when slightly changing the gas-liquid separator design in order to introduce the mixture of tetrahydridoborate with hydrochloric acid to the bottom of the...
Possibilities of electrochemical generation of volatile compound of thallium
Marschner, Karel ; Hraníček, Jakub (advisor) ; Rychlovský, Petr (referee)
The possibilities of electrochemical generation of volatile thallium hydride have been studied in this work. A thin-layer electrolytic cell with minimal volume of cathode chamber has been employed. All experiments have been employed in electrochemical continuous flow generation. An electrochemical hydride generation technique was developed to improve the determination of analytes by atomic spectrometry. Effect of various experimental conditions such as kind of cathode material, type and concentration of electrolyte, amount of generation current and flow rate of carrier gas on the absorption signal was examined. Under the optimal values of previously mentioned parameters, the low sensitivity of thallium determination was achieved. So the experimental setup is not suitable for determination of low concentration of thallium in specimens. Keywords Atomic absorption spectrometry, electrochemical generation of volatile compounds, hydrides, thallium, electrolytic flow cell, optimization
Arsenic speciation by hydride generation coupled with atomic fluorescence spectrometry
Marschner, Karel ; Musil, Stanislav ; Rychlovský, P. ; Dědina, Jiří
Post-column hydride generation for arsenic speciation was used and the demethylation of Arsenic species during hydride generation was investigated.
Efficient generation of arsanes coupled with HPLC or with cryotrapping for speciation analysis of arsenic
Marschner, Karel ; Musil, Stanislav ; Rychlovský, P. ; Dědina, Jiří
Arsenic speciation analysis by HPLC postcolumn hydride generation or with cryotrapping and detection by atomic fluorescence spectrometry.
Arsenic speciation analysis by HPLC postcolumn hydride generation and detection by atomic fluorescence spectrometry
Marschner, Karel ; Musil, Stanislav ; Rychlovský, P. ; Dědina, Jiří
The aim of this contribution is to present a new method of hydride generation that enables to generate arsines from iAs , iAs , MMA and DMA in a flow injection mode with the same efficiency and in the next step connection of this hydride generator with HPLC column.

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