National Repository of Grey Literature 5 records found  Search took 0.00 seconds. 
UV-photochemical generation of volatile selenium compounds for ultratrace analysis by AAS
Rybínová, Marcela ; Rychlovský, Petr (advisor) ; Komárek, Josef (referee) ; Šíma, Jan (referee)
This thesis deals with the study of UV-photochemical generation of volatile compounds (UV-PVG) in connection with atomic absorption spectrometry (AAS). Selenium (Se(IV)) was selected as a model analyte and many experiments were carried out to expand the current sum of knowledge of the topic. The study was commenced by assembling the UV-PVG apparatus in the continuous flow mode. The detection method used was AAS with externally heated quartz furnace atomizer. The focus of the first step of the study was on the construction of the volatile compounds generator (UV-photoreactor) with emphasis on the material used; tubes made of teflon or quartz of different diameters were tested. The construction of the apparatus was followed by optimization of the reaction conditions (the type and concentration of the photochemical agent and other agents, which increase the analytical signal; the carrier gas and the auxiliary hydrogen gas flow rate; the sample flow rate). Eventually, the analytical figures of merit of the selenium determination using the proposed method were found. The results showed that teflon reaction tubes are a good competitor to those made of quartz. The accuracy of the method has been successfully verified by analysis of certified reference material and its applicability has been further tested...
UV-photochemical generation of volatile selenium compounds for ultratrace analysis by AAS
Rybínová, Marcela
This thesis deals with the study of UV-photochemical generation of volatile compounds (UV-PVG) in connection with atomic absorption spectrometry (AAS). Selenium (Se(IV)) was selected as a model analyte and many experiments were carried out to expand the current sum of knowledge of the topic. The study was commenced by assembling the UV-PVG apparatus in the continuous flow mode. The detection method used was AAS with externally heated quartz furnace atomizer. The focus of the first step of the study was on the construction of the volatile compounds generator (UV-photoreactor) with emphasis on the material used; tubes made of teflon or quartz of different diameters were tested. The construction of the apparatus was followed by optimization of the reaction conditions (the type and concentration of the photochemical agent and other agents, which increase the analytical signal; the carrier gas and the auxiliary hydrogen gas flow rate; the sample flow rate). Eventually, the analytical figures of merit of the selenium determination using the proposed method were found. The results showed that teflon reaction tubes are a good competitor to those made of quartz. The accuracy of the method has been successfully verified by analysis of certified reference material and its applicability has been further tested...
Generation of volatile species of copper for atomic absorption spectrometry
Šoukal, Jakub ; Musil, Stanislav (advisor) ; Rybínová, Marcela (referee)
This thesis deals with optimization of conditions of chemical generation of volatile species of copper for atomic absorption spectrometry. The volatile species of copper were generated in the flow arrangement in a special generator by the reaction of the acidified sample with the solution of sodium borohydride in the presence of reaction modifiers. A diffusion flame was used as the atomizer of volatile species of copper due to its high robustness. First, all the parameters affecting atomization in the diffusion flame were optimized (flow rates and composition of gases, observation height). In the next section, concentration of individual reagents for chemical generation of volatile species was optimized, especially the concentration of nitric acid, sodium borohydride and reaction modifiers. Triton X-100 and Antifoam B were chosen as the best combination of modifiers with respect to threefold increase in sensitivity, tailing of measured signals and because of long-term repeatability. There was not observed any significant positive effect on the sensitivity of measurement for other tested reaction modifiers. The limits of detection and quantification were 62 mg dm−3 and 208 mg dm−3 , respectively. The repeatability of this method for concentration 2,5 mg dm−3 was 2,4%. Key words copper, chemical...
Speciation analysis of chromium in particulate matter of urban dust
Rybínová, Marcela ; Hraníček, Jakub (referee) ; Rychlovský, Petr (advisor)
Anion-exchange chromatography with inductively coupled plasma - atomic emission spectrometry (ICP-AES) has been used for the speciation of chromium (Cr). Chromium speciation has attracted attention because of the different toxicity, Cr(III) is relatively non-toxic and Cr(VI) has been classified as a human carcinogen. The aim of the present study was to develop simple method for the speciation analysis of Cr (Cr(III) and Cr(VI)) in particulate matter of urban dust. A combination of 2% KOH + 3% Na2CO3 has been chosen as the optimal reagent for the extraction of chromium from particular matter. It was found that there was no conversion of Cr(VI) into Cr(III). The effect of separation parameters such as acidity of mobile phase was also studied. The detection limit for Cr(VI) was about 12 ng.ml-1 . Results for the determination of Cr(VI) were confirmed by the analysis of standard reference material (BCR CRM 545, Cr(VI) in welding dust loaded on a filter) with good agreement between certified (40,16 ± 0,60 μg.g-1 ) and found (37,83 ± 1,14 μg.g-1 ) values.

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1 Rybínová, Marta
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