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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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Determination of chlorobenzoic acids in environmental samples using separation techniques with mass detection
Hostačná, Lucie ; Bosáková, Zuzana (advisor) ; Čabala, Radomír (referee)
Chlorobenzoic acids are a major environmental contaminant. The main source of contamination of environmental matrix is a bacterial dergadation of polychlorinated biphenyls. In this work, it has been optimized a method for the determination of 15 chlorobenzoic acid derivates (2-CBA; 3-CBA; 4-CBA; 2,3-CBA; 2,4- -CBA; 2,5-CBA; 2,6-CBA; 3,4-CBA; 3,5-CBA; 2,3,5-CBA; 2,3,6-CBA; 2,4,6- -CBA; 2,3,4,5-CBA; 2,3,5,6-CBA a 2,3,4,5,6-CBA) in the soil matrix, including accelerated solvent extraction, purification by gel permeation chromatography, derivatization and subsequent quantification of samples by GC/MS. As the extraction conditions were used: an extraction mixture of 1% acetic in hexane/acetone (1:1 V/v), temperature by 150 řC, pressure by 10,34 MPa. For purification by gel permeation chromatography solvent was used dichloromethane. Derivatization with diazomethane was determined in the range of 83,7 to 110,6 % with relative standard deviation from 2,1 to 14,2 %. Aplication of the optimized method of the artificially contaminated soil samples in the analysis of GC/MS provided the yield of all analytes in the range of 91,7 to 132,5 % with relative standard deviation from 2,1 to 12,1 %. Validation of methods after aplication to GC/MS gave the analytes 2- -CBA; 3-CBA; 4-CBA and 2,3,4,5-CBA the limit of...
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Development of separation methods for determination of perfluoroalkyl carboxylic acids in envirnonmental samples
Dufková, Veronika ; Čabala, Radomír (advisor) ; Feltl, Ladislav (referee) ; Kubinec, Róbert (referee)
A complete, sensitive and selective procedure was developed for gas chromatographic determination of perfluoroalkyl carboxylic acids (PFCAs, C5 - C12) in river water samples. A rapid and simple derivatization procedure was developed and optimized at first, using isobutyl chloroformate (IBCF) to convert the acids into the more volatile isobutyl esters. The second task was to find the most suitable stationary phase for separation of perfluoroalkyl carboxylic acids by GC. The retention characteristics of PFCA isobutyl esters were measured and compared on 9 different stationary phases. The physical-chemical parameters of analyte interactions with stationary phase were monitored on selected column Rtx-200MS, and these parameters were compared with a non-fluorinated homologue - octanoic acid. A sensitive GC-MS system was used with negative chemical ionization, which is suitable for the selected type of fluorinated analytes. The developed method exhibits very low limits of detection and determination of PFCA isobutyl esters: 0.05 - 9.7 ng mL-1 (LOD) and 0.16 - 32.2 ng mL-1 (LOQ). An optimum pre-concentration technique was found for real water samples, where SPE SupelTM-Select HLB cartridges were used. In these cartridges, PFCAs were captured as ion- pairs with enrichment factor of 400. The recoveries of...
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Determination of Sibiromycin by UPHLC Method
Šestáková, Ivana ; Čabala, Radomír (referee)
A new separation and quantification method using ultra high-performance liquid chromatography (UHPLC) with UV detection was developed for the detection of sibiromycin in fermentation broth of Streptosporangium sibiricum. The solid phase extraction method based on cation-exchange was employed to pre-concentrate and purify fermentation broth containing sibiromycin prior to UHPLC analysis. The whole assay was validated and showed a linear range of detector response for the quantification of sibiromycin in a concentration from 3.9 to 250.0 µg/ml, with correlation coefficient of 0.999 and recoveries rating from 71.66±3.55 % to 74.75±5.18 %. Method limit of quantification of the assay was determined as 0.18 µg/ml and was verified with resulting RSD of 9.6 % and accuracy of 97.6 %. The developed assay was used to determine the sibiromycin production in 12 different fermentation broths. Moreover, several natural sibiromycin analogues/derivatives were described with pilot characterization using off-line mass spektrometry.
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Analysis of pterine derivatives by capillary zone electrophoresis
Krajíček, Jan ; Bosáková, Zuzana (advisor) ; Čabala, Radomír (referee)
Pterins belong to an important group of compounds, acting as inhibitors, sensiziters, enzymes, coenzymes, pigments etc. and together with carotenoids and anthraquinones are responsible for characteristic coloration of bugs. This work was focused on the development of a capillary electrophoretic separation method for the analysis of six pterine derivatives, namely biopterine, neopterine, isoxanthopterine, leukopterine, xanthopterine and erythropterine and on their identification in the real samples. Separation was conducted in an uncoated fused-silica capillary termostated at 30 řC. Separation electrolyte contained boric acid, tris(hydroxymethyl)aminomethane and disodium salt of ethylenediaminetetraacetic acid. The effects of buffer pH, concentration of electrolyte components, separation voltage and wavelength of UV detection on electromigration behavior and detection sensitivity were studied. Under the optimized separation conditions, organic extracts of the three forms of Graphosoma semipunctatum bugs were analyzed.
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Determination of selected chromatographic and thermodynamic parameters of perfluorinated organic acids by gas chromatography
Vrzal, Tomáš ; Čabala, Radomír (advisor) ; Pacáková, Věra (referee)
Chromatographic and thermodynamic parameters (specific retention volume, distribution coefficient, standard molar enthalpy, entropy and Gibbs energy) has been determined for retention of isobutyl esters of homological set of perfluorinated carboxylic acids C6 - C12 on the fluorinated stationary phase Rtx-200MS. Determined data has shown, that distribution of solutes between stationary and mobile phase is driven neither by the enthalpy nor entropy, but both these contributors play the same role in the retention mechanism. Helium and hydrogen has been used as a mobile phases during analysis. Their influence on thermodynamic behavior of isobutyl esters of PFCAs is insignificant.
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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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