McCormack Raymond (motioncarrot1)

8% to 114.4%.In this study, amylose- and cellulose-phenylcarbamate-based chiral columns with different chiral-selector (CS) chemistries were compared to each other for the separation of enantiomers of basic chiral analytes in acetonitrile and aqueous-acetonitrile mobile phases in HPLC. For two chemistries the amylose-based columns with coated and immobilized CSs were also compared. The comparison of CSs containing only electron-donating or electron-withdrawing substituents with those containing both electron-donating and electron-withdrawing substituents showed opposite results for the studied set of chiral analytes in the case of amylose and cellulose derivatives. Along with the chemistry of CS the focus was on the behavior of polysaccharide phenylcarbamates in acetonitrile versus aqueous acetonitrile as eluents. In agreement with earlier results, it was found that in contrast to the commonly accepted view, polysaccharide phenylcarbamates do not behave as typical reversed-phase materials for basic analytes either. In the range of water content in the mobile phase of up to 20-30% v/v the behavior of these CSs is similar to hydrophilic interaction liquid chromatography (HILIC)-type adsorbents. This means that with increasing water content in the mobile phase up to 20-30% v/v, the retention of analytes mostly decreases. The important finding of this study is that the separation efficiency improves for most analytes when switching from pure acetonitrile to aqueous acetonitrile. Therefore, in spite of reduced retention, the separation of enantiomers improves and thus, the HILIC-range of mobile phase composition, offering shorter analysis time and better peak resolution, is advantageous over pure polar-organic solvent mode. Interesting examples of enantiomer elution order (EEO) reversal were observed for some analytes based on the content of water in the mobile phase on Lux Cellulose-1 and Lux Amylose-2 columns.A method for the preparation of an on-column ESI emitter used as the sheathless interface for coupling capillary electrophoresis (CE) with mass spectrometry (MS) was developed. The emitter was directly fabricated at the outlet end of the separation capillary which was etched with HF solution to a symmetrical tip. The tip was covered with a small piece of gold foil which was fixed by epoxy resin glue for electrical contact. Such a prepared ESI emitter can produce a stable ESI signal over the wide range of flow rate from 50 nL/min to 800 nL/min. The performance of the CE-MS with the sheathless interface was evaluated by using the separation of four alkaloids. It was found that the strong electroosmotic flow produced by the multiple polyelectrolyte coating on the capillary is necessary for maintaining a stable MS signal. Effect of the running buffer composition, concentration and the CE separation voltages on the ESI signal strength were investigated. The absolute detection limits for the alkaloids was determined as fmol level. Moreover, the CE-MS was applied for the analyses of trypsin digestion of cytochrome C and small molecular organic anions. The emitter performed very stable with a lifetime of at least 180 h.Oxylipins, the oxidation products of polyunsaturated fatty acids, are important signaling molecules in living organisms. Some of them have pro-inflammatory properties, while others act as pro-resolving agents. Oxylipins also play a major role in platelet biology and the progression of thrombo-inflammation. Depending on their structure, they may be pro-thrombotic or anti-thrombotic. For an unbiased biological interpretation, a detailed analysis of a broad spectrum of oxylipins including their stereoisomers is necessary. In our work, we developed for the first time an enantioselective UHPLC-ESI-MS/MS assay which allows quantifying individual oxylipin enantiomers. The assay made use of a sub-2µm particle-based amylose-(3,5-dimethylphenylcarbamate) chiral stationary phase (Chiralpak IA-U) under MS-compatible reversed-ph