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Structure and reactivity of anions of aromatic hydrocarbons
Obluková, Michaela ; Čabala, Radomír (advisor) ; Jašík, Juraj (referee)
This bachelor thesis deals with research about negative ions reactivity of aromatic hydrocarbons which occur in Titan's ionosphere - Saturn's moon. As an experimental method there was used tandem mass spectrometry with electrospray ionization technique, quadrupole mass analyzer and collision cell. The aim of this thesis was to contribute to the general understanding of processes in the Titan's ionosphere. Particularly there were performed experimental studies to created isomeric benzyne radical anions (o-, m-, p- C6H4˙- ) which were generated from phthalic, isophthalic and terephthalic acid and subsequently their reactions were explored with selected neutral gases in collision cell (C2H2, HC3N, CH3CN, SO2, O2).
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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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Optimization of conditions for derivatization of fatty acids and perfluorinated organic acids with methylchloroformate
Hložek, Tomáš ; Čabala, Radomír (advisor) ; Feltl, Ladislav (referee)
Statistical methods designed for optimization were applied for selection of optimal experimental conditions of derivatization process for perfluorinated acids, PFA (C8, C10 ,C12), fatty acids, FA (C8, C12, C14) and their mixtures. The calibration curves and the extraction efficiences for system acetonitrile/heptane were measured for all studied acids. The Plackett-Burman screening was performed for obtaining the significant experimental parameters from their original series and significant ones were remitted to optimization via central composite design, which takes a second order effects and mutual interactions in between parameters into account. Optimal conditions of derivatization were found for PFA, FA and their mixtures. The principle of the search of optimal selective derivatization conditions for one group of acids in the presence of the other is based on the search of optimum on the response surface where the dependent variable is either sum or difference of acid group responses normalized to common internal standard. It was found that FA influence total response more than PFA and that in the case of demand for selective derivatization of PFA in the presence of FA in the sample, the most significant parameter is the volume of methylchloroformate added. The complete selectivity of...
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Study of peptide digestion kinetics by trypsin and chiral separations of biologically active compounds by HPLC
Šlechtová, Tereza ; Tesařová, Eva (advisor) ; Čabala, Radomír (referee) ; Mikšík, Ivan (referee)
This dissertation thesis composes of two parts; the first part focus on the characterization of trypsin, enzyme frequently used in proteomic research for the investigation and identification of protein sequences, and its peptide digestion kinetics. The second part is aimed to the enantioseparations of biologically active compounds. First part of this project focus on tryptic digestion of synthetic peptides and the development of HPLC method for the identification of synthetic peptides and their fragments. Using the in-solution digestion and HPLC method, relative kinetic constants were determined for problematic sequences. Amino acids responsible for the decrease in trypsin catalytic activity and their location towards the cleavage site were studied. Certain slight exopeptidase activity of trypsin was noted, especially at the end of peptide chain. Furthermore, three columns with immobilized trypsin used in HPLC were compared concerning their catalytic activity. The immobilization of enzymes on solid support is used to elevate the amount of enzyme present during digestion and to assure better repeatability and reproducibility of obtained results. Activity of a new trypsin column synthesized at the University of North Carolina at Chapel Hill was compared to two commercially available trypsin columns....
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Analysis of selected pterins and their extracts from integument of Pyrrhocoris apterus by HPLC-MS/MS
Vejvodová, Tereza ; Bosáková, Zuzana (advisor) ; Čabala, Radomír (referee)
This diploma thesis was focused on the development of a separation method for qualitative analysis of twelve chosen pterin derivates by hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry detection. Two silica gel-based columns with different ligands attached were used for the chromatographic separation - a ZIC-HILIC column containing sulfobetaine as a ligand and a ZIC-cHILIC column containing phosphorylcholine as a ligand. The optimizing procedure was performed to achieve sufficient separation of the analytes in an acceptable time. Therefore, the effect of the amount of organic modifier in mobile phases and salt concentrations and the pH of the aqueous phase on the separation of pterin derivatives was studied. Under the optimized separation conditions (column ZIC-HILIC, mobile phase composition 83/17 (v/v) acetonitrile/10 mM ammonium acetate, pH 6.8) the method was used for the analysis of extracts from the integument of Pyrrhocoris apterus. The extracts were obtained using five different extraction systems, namely acetonitrile, methanol, dimethyl sulfoxide (DMSO) and two types of so-called deep eutectic solvents containing a mixture of choline chloride and lactic acid (DES 1) and a mixture of choline chloride and ethylene glycol (DES 2). DMSO was shown to be the...
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Optimization of experimental conditions for measurements of perfluorinated organic acids by GC
Ston, Martin ; Čabala, Radomír (advisor) ; Coufal, Pavel (referee)
Commercial software Pro ezGC was used for calculation of optimal temperature program for analysis of isobutylesters of perfluorinated organic acids (C6 - C12) by gas chromatography with flame ionization detector. Optimization was done with respect to the complete resolution of all peaks of analytes. The calculated temperature program was also applied to the analysis of substances of interest on GC-MS. The calculated and measured values have been compared. The measured resolutions were higher than the calculated ones in all cases. Keywords: perfluorinated organic acids, isobutylesters, peak resolution Subject words: gas chromatography, numerical optimization
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Development of analytical methods for determination of phosphorylated components of bacterial cell membranes
Mikulecká, Jana ; Čabala, Radomír (advisor) ; Feltl, Ladislav (referee)
Phospholipids are dominant components of bacterial cell membranes, where they create double layers. Bacteria differ in their phospholipid composition determination of which can help in identification of important groups of microorganisms. Phospholipid composition of bacteria is influenced by many environmental factors, therefore its variation can be observed within one bacterial stem also. Because of its simplicity, thin layer chromatography is usually applied to identification and determination of bacterial phospholipids. Disadvantage of this method are the high demands of time, carefulness and skills of the analytical personnel. The increasing interest in the phospholipid double-layer promotes the detailed investigation of their fatty acid composition because the more detailed analyses allows for more information yield about bacteria. Gas chromatography hyphenated with mass spectrometry seems to be the best choice for these purposes. Fatty acid identity and total fatty acid content in phospholipid molecules could be determined by this method. Additionally, number, position and isomerism of double bonds and presence of other functional groups on hydrocarbon chain could be determined. Whereas a suitable and...
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Determination of niacin and its metabolites by HPLC-MS
Pultarová, Kamila ; Čabala, Radomír (advisor) ; Staňková, Barbora (referee)
Nicotinic acid (NA) is a hypolipidemic agent with pleiotropic effects on plasma lipoproteins. Its medicamentous form with delayed secretion leads to pyrimidine metabolites, which make increased risk of hepatotoxicity and should be monitored. The aim of the presented study was to introduce HPLC-MS method for the determination of NA, nicotinamide (NAM), nicotinuric acid (NUA), 1-methyl-nicotiamide (MNA), nicotinamid-N-oxide (NNO), 1-methyl-2-pyridon-5-carboxamide (2-Pyr) and 1-methyl- 4-pyridon-5-carboxamide (4-Pyr) in blood plasma useful for the monitoring of hypolipidemic therapy. We have compared calibration dependences of individual metabolites using two columns - Hypercarb (grapfite carbon) and Hypersil Silica (silicagel). Both columns revealed linear calibration dependences for all mentioned analytes except MNA in the concentration range 10-2000 ng/ml for chemical standards; calibration dependence in human blood plasma measured with the column Hypersil Silica was linear in the range 20-4000 ng/ml for all tested analytes. Correlation coefficient varied between the value 0,9400 and 0,9997. Analysis time was 15 min with the column Hypercarb and 27 min with Hypersil Silica. Biological samples were extracted using solid phase with sulphonyl group. Reproducibility of the results of biological samples...
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