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Testing and optimization of pressure modulator conditions for GCxGC analyses
Ston, Martin ; Čabala, Radomír (advisor) ; Jelínek, Ivan (referee)
Pulse (fluid) pressure modulator was constructed for comprehensive gas chromatography. Optimal conditions of its connection to the gas chromatograph with a flame ionization detector were found for the analysis of selected mixture of volatile solvents. Pressure interdependences in the system and relations between dimensions of modulator capillaries and columns have been evaluated with respect to the length of the modulation period and pulse duration. Two non-polar columns (15 m × 0.25 mm DB-5MS, 10 m × 0.15 mm CP-Sil 5 CB) of the same stationary phase were tested to compare the separation efficiency in the first dimension and the DB-5MS column was selected. The Supelcowax 10 columns of the lengths 1, 2 and 3 m were compared in the second dimension. It was found that using of 3 m length column lead to the extension of analysis time, however the increase in separation efficiency in the second dimension was very evident. The experimental measurements have shown that the selected parameters for the evaluation of the separation efficiency (the peak capacity and total resolution product) were inappropriate. Gasoline, kerosene and diesel fuel were analyzed as examples of real samples. Amount of added ethanol as a biofuel additive was determined in the gasoline sample. Pulse pressure modulator was modified...
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Preparation of modified gold electrodes for quartz microbalance
Králová, Miroslava ; Jelínek, Ivan (advisor) ; Čabala, Radomír (referee)
This diploma work is devoted to the preparation and analytical testing of modified gold electrodes in QCM. The sensitivity and selectivity response towards selected aromatic analytes in aqueous phase was monitored. Studied analytes were 1-methylnaphthalene, 2-methylnaphthalene, naphthalene, o-xylene and toluene. These compounds are frequently used in chemistry industry and other industrial branches and, are known to be harmful to human organism and environment. Using QCM method it is possible to detect them rapidly and relatively easily.
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Development and optimization of SPE method for preconcentration and determination of fluorotelomeric alcohols in water
Ševčík, Václav ; Čabala, Radomír (advisor) ; Feltl, Ladislav (referee)
New GC-MS method combined with SPE preconcentration step has been developed and optimized for the determination of selected fluorotelomer alcohols in aqueous samples by advanced statistical method in this thesis. 1H,1H,2H,2H-perfluoro-1-octanol (6:2 FTOH) and 1H,1H,2H,2H-perfluoro-1-decanol (8:2 FTOH) have been selected as the analytes. The influence of several factors, such as the sample volume, the carrier gas pressure, the sampling time and the injector temperature on the system response have been studied during the optimization. Utilizing the statistical software Minitab 16 and series of experiments, the optimal values of relevant factors and a suitable type of ionization were found for both analytes. Limits of detection of GC-MS method are 0.24 ng/mL for 6:2 FTOH and 0.42 ng/mL for 8:2 FTOH. Several factors, such as the type and the volume of conditioning agent, the speed of conditioning, the speed of sample flow, the method of column drying, the type and the volume of eluent have been tested for SPE. The optima of these factors were determined using Minitab 16 software. The extraction efficiency dependence on the concentration and volume of the stock solution was used to set the limitation of SPE for the determination of fluorotelomer alcohols. The maximum volume of sample equals to 400 mL...
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Determination of polycyclic aromatic hydrocarbons in hydrosphere solid matrices by QuWChERS - comparision with present methods
Sudová, Petra ; Nesměrák, Karel (advisor) ; Čabala, Radomír (referee)
Thesis are aimed to the optimization and validation of the QuEChERS method for determination of polycyclic aromatic hydrocarbons in solid matrices of hydrosphere. The QuEChERS method was also used for determination of polycyclic aromatic hydrocarbons in real samples and for comparison of measured results, time and material costs of the method with currently employed methods: (1) accelerated solvent extraction connected with gel permeation chromatography (ASE/GPC), and (2) ultrasonic extraction connected with solid phase extraction (UZ/SPE). According to the validation criteria, the QuEChERS method is suitable for the determination of polycyclic aromatic hydrocarbons in solid matrices of hydrosphere. The QuEChERS technique provides comparable results to ASE/GPC and UZ/SPE. In terms of price and time for sample preparation, the QuEChERS method allows (unlike the methods ASE/GPC and UZ/SPE) fast and inexpensive determination of polycyclic aromatic hydrocarbons in solid samples of hydrosphere.
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Analysis of organic additives in historical mortars
Křížová, Iva ; Čabala, Radomír (advisor) ; Hynek, Radovan (referee)
- 4 - Abstrakt The aim of this diploma thesis was to determine the possibility of identifying the protein and lipid additives, such as blood, gelatine, curd, lard and eggs, in the model samples of lime based mortars using Raman spectroscopy and gas chromatography- mass spectrometry. It was proved that the method of Raman spectroscopy can determine the presence of organic additives in the order of one weight percent. The gas chromatography enables to detect lipid additives from the order of hundredths weight percent. Unambiguous resolution of protein additives can be done in the samples with the concentrations up to the order of one weight percent of the additives.
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Ambient ozon impact on vegetation
Bystrianský, Martin ; Hůnová, Iva (advisor) ; Čabala, Radomír (referee)
Bystrianský: Ambient ozone impact on vegetation - Abstract Ambient ozone is present in the air all around the world. It is natural component of the atmosphere, due to anthropogenic emissions of ozone precursors its concentration rise. That is unlikely, because ozone is toxic. Ozone is formed as a part of photochemical smog from ozone precursors by photochemical reactions. As ozone precursors nitrogen oxides (NOx) and volatile organic compounds (VOC) are called. Their main source is car traffic. Danger of ozone lies in its reactivity. It oxidizes most of organic compounds, especially those containing double bonds. These are present in membrane lipids. Furthermore, ozone forms more reactive compounds than itself - active oxygen species (AOS), free radicals. Ozone effects negatively both human health and vegetation. Ozone disrupts structure of the cells, which for plants means destroy of leaves and needles, photosynthesis disruption and biomass loss. For that, plants have antioxidants system for AOS scavenging. But it has little effect, when concentration of ozone is high during smog period. Therefore, limits for maximal concentration of ozone in the ambient air are set.
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SPE optimization for determination of perfluorinated organic acids
Ševčík, Václav ; Čabala, Radomír (advisor) ; Pacáková, Věra (referee)
This thesis is focused on optimization of preparation of aqueous environmental samples for determination of persistent pollutants - perfluorinated organic acids, which are potentially dangerous for living organisms. The goal of the thesis is optimization of SPE conditions for preconcentration of these compounds for their determination by GC-MS. Perfluorinated organic acids with carbon chain lenghts of C6-C12 were selected as analytes. Effect of sample pH value, effect of type and elution solvent volume, addition of indifferent salt and ion pair reagent have been studied during the optimization. The results show that the extraction efficiency depends on analyte carbon chain length and reaches values from 75 to 110 % for C6 - C8 and 55 to 95 % for C9 - C12 acids. The overall increase in extraction efficiency was more pronounced for acids with shorter chain length (for C6 up to ten times), whereas for long chain acids the improvement was only moderate.
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Toxicity determination of polyfluorinated and perfluorinated organic substances
Otrubová, Lucie ; Čabala, Radomír (advisor) ; Rucki, Marian (referee)
The goal of the bachelor thesis was the determination of toxicity of fluorotelomer alcohols. The toxicity was measured as ET50 by the oligochaete Tubifex tubifex. This test belongs to group of alternative methods which are faster and cheaper but they provide reliable data as well as the presently used classical methods. ET50 is the exposure time when 50 % of Tubifex tubifex individuals stop moving. EC50 of magnese chloride dihydrate was measured for the control of its correctness of determination and its acute toxicity indice is equal to log (EC50) = -0,845 ± 0,033 [log (mmol/l)]. EC50 is the concentration of the tested substance when 50 % of Tubifex tubifex individuals stop moving. 1H,1H,2H,2H-perfluorooctan-1-ol and 1H,1H,2H,2H-perfluorodecan-1-ol were the tested substances. Destilled water and solution of dimethyl sulfoxide in water (5 %) were used to prepare the saturated solutions of the tested substances. The conncentrations of the saturated solutions were determined on GC-MS by absolute calibration method. The value of log (EC50) for dimethyl sulfoxide solution was measured to determine how it influences Tubifex tubifex during exposure time of 2,5 hours. KEY WORDS: fluorotelomer alcohols, alternative method, Tubifex tubifex
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