|
|
Polymethacrylate monolithic columns in capillary liquid chromatography
Grafnetter, Jan ; Coufal, Pavel (advisor) ; Pacáková, Věra (referee) ; Ventura, Karel (referee) ; Sýkora, David (referee)
3 Conclusions This Thesis gives chromatographic and structural characteristics of the butyl methacrylate monolithic columns prepared for the capillary liquid chromatography. Results of this Thesis clearly demonstrate the possibility of preparation of capillary monolithic columns with a good repeatability of the principal chromatographic parameters. A completely new technique for preparation of the monolithic columns for use in the on-column detection mode was introduced. Different photometric detection modes were applied to monolithic capillary columns in CLC. The advantages and disadvantages of the on-column detection mode in comparison to the additional detection capillary were studied and described. It was shown that the best separation and the most sensitive quantification in the short analysis time could be reached by using the monolithic columns with detection window placed directry on the separation capillary, just after the stationary phase or within the monolith. The attempts leading to preparation of chiral monolithic stationary phases, which would allow enantioseparation of selected chiral analýes' were not totally successful. No time was left to find the suitable chromatographic conditions for enantioseparations. \ I
|
|
|
New procedures in metabolomic analysis of biofluids
Řimnáčová, Lucie ; Čabala, Radomír (advisor) ; Feltl, Ladislav (referee) ; Sýkora, David (referee)
The aim of this thesis has been the research on reactivity of protic metabolites with chloroformates and its application for GC-MS analysis of biofluids. The research was conducted in three separate studies and the results are three new, original methods for GC-MS determination of low- molecular protic metabolites in biological material especially in biofluids. The first study explores the discovery of fast derivatization of alicyclic hydroxyl groups by fluoroalkyl chloroformates (FCFs) under anhydrous conditions [1]. FCF fully converts the hydroxyl group into a corresponding carbonate and the step can easily be coupled with liquid-liquid microextraction (LLME) of the arising derivatives into organic phase. The reaction of the alicyclic OH group with FCFs was tested on 12 clinically relevant steroids and 4 tocopherols. The analytical properties of determined analytes were described and the method was validated for the GC-MS determination of 6 diagnostic sterols and 4 tocopherols in human serum and amniotic fluid. The new method was further successfully used for determination of sterols and tocopherols in tissues of the bug Pyrrhocoris apterus [2]. The second study was focused on the reactions of protic, particularly urinary metabolites with FCFs, mainly heptafluorobutyl chloroformate (HFBCF)....
|
|
|
Application of solvation mocel to retention description of selected compounds in liquid and gas chromatography
Jirkal, Štěpán ; Čabala, Radomír (advisor) ; Feltl, Ladislav (referee) ; Sýkora, David (referee)
(EN) The solvation model based on LSER was applied to study the retention behaviour of analytes in liquid and gas chromatography. In a first chapter, a retention description of 21 solutes was investigated by using the solvation model in a wide range of mobile phase composition methanol-water and acetonitrile-water. Generally, the retention of aromatic compounds was better described by the solvation model, compared to aliphatic compounds. Effect of the particular analytes used to formulate the LSER model on ability of retention description was studied. Different results of a retention estimation was achieved by using the regression set of compounds including aromatic solutes only or by contrast aliphatic solutes only. The solvation model developed on the basis of oxygen derivatives provided distinct results in comparison to model formulated with nitrogen derivatives only. The second chapter of this work, focused on gas chromatography, dealt with a description of retention of 152 isomers C5-C8 alkenes by the LSER model. The solvation descriptor L was obtained by using two estimation methods Havelec-Ševčík (HS) and Platts-Butina (PB), the descriptor E was calculated according to its definition. Two models for retention description of alkenes were constructed, the HS model and the PB model, derived...
|
|
|
Characterization of new chiral separation systems for HPLC
Vozka, Jiří ; Tesařová, Eva (advisor) ; Sýkora, David (referee) ; Petr, Jan (referee)
The dissertation thesis is focused on the physico-chemical characterization of interaction mechanisms of chiral stationary phases based on derivatized cyclofructans. Correct interpretation of retention and enantiodiscrimination processes substantially facilitates the development and optimization of new enantioselective methods using cyclofructan-based chiral stationary phases. At first, the interaction mechanisms of three commercially available cyclofructan-based stationary phases were studied in normal-phase mode of liquid chromatography. Namely, systems using chiral stationary phases based on dimethylphenyl carbamate cyclofructan 7, R-naphtylethyl carbamate cyclofructan 6 and isopropyl carbamate cyclofructan 6 were studied. Linear free energy relationship model was used as a basic tool for characterization of interactions on the stationary phases. The mentioned model revealed that the main interactions contributing to retention in cyclofructan-based systems are hydrogen bond acidity and dipolarity/polarizibility, while dispersion interactions cause decrease of retention. The impact of oligosaccharide skeleton of the cyclofructan selector on the enantioselectivity was elucidated by the comparison with seemingly analogous cyclodextrin-based chiral stationary phases. Cyclofructan-based chiral...
|
|
|
Liquid chromatography methods for analysis of microbial secondary metabolites of bioactive nature
Tylová, Tereza ; Olšovská, Jana (advisor) ; Cvačka, Josef (referee) ; Sýkora, David (referee)
(EN) This work is focused on development of new analytical methods involving modern solid phase extraction (SPE) for sample purification and pre-concentration, state-of-art ultra high- performance liquid chromatography (UHPLC) for separation of analytes and detection using diode-array detection (DAD) and/or time-of-flight mass spectrometry (ToFMS). The major part of the results has been published in prestigious international journals. The relevant yet unpublished results are included in the thesis as well. Besides a model comparison of various column chemistries used for "ultra-high performance" separations, some meaningful applications were developed. While one part of applications deal with determination of antibiotics as environmental contaminants that are responsible for the development and spread of microbial resistance, the second part is concerned with analyzing and finding of potential natural source of novel antimicrobial agents that can be further used as new antibiotics. The first part of the thesis was focused on the determination of residual antibiotics in different matrices (liquid hog manure, wastewater, surface water). The mostly prescribed antibiotics in both human and veterinary medicine were chosen as analytes in this study employing analytical methods consisting of UHPLC-DAD and...
|
|
|
Modern separation and spectrometric techniques for biological sample lipidom investigation
Havelková, Eva ; Bosáková, Zuzana (advisor) ; Sýkora, David (referee)
Modern separation and spectrometric techniques for biological sample lipidom investigation Due recent progress in field of mass spectrometry the lipidomics, part of metabolomics, is increasing its importance for broad fields of biological study. The aim of this study is to test the lipid extraction techniques and to optimize the preseparation and separation of lipids suitable for mass spectrometry detection. The fragmentation patterns of four, the most abundant lipid classes of glycerolipids (PC, PE, TG, DG), were acquired for the proposed system. These patterns were compared with literature. The most appropriate method for extraction was declared technique according Folch based on methanol and chloroform solution. The preseparation due SPE method is very useful tool for lipid determination. The optimized were focused to reach higher recovery especially in polar lipid fraction. Proposed HPLC system is based on methanol with ammonium buffer, water and isopropanol. The testing was done on three columns with different type of sorbents (Gemini, Syncronis and Kinetex). The separation was evaluated according mass spectrometer response, shape and wide of particular analytes peaks. Composition contains 20% of water was determinate as the best and also the best separation was achieved by Kinetex column. The proposed...
|
guest ::
RSS feed.