Structural Characterization and Quantitative Analysis by Interfacing Liquid Chromatography And/or Ion Mobility Separation with Multi-dimensional Mass Spectrometry

Download or read book Structural Characterization and Quantitative Analysis by Interfacing Liquid Chromatography And/or Ion Mobility Separation with Multi-dimensional Mass Spectrometry written by Nilüfer Solak and published by . This book was released on 2010 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This dissertation focuses on coupling liquid chromatography (LC) and/or ion mobility (IM) spectrometry to mass spectrometry (MS) and their application to characterization of complex mixtures. Fatty acid ethyl esters (FAEEs) in meconium, polyethylene oxide (PEO) copolymers, the nonionic surfactant Polysorbate 85, and poly(butylene adipate) were characterized by LC-MS[superscript n] and/or IMMS[superscript n]. Coupling of a separation technique to mass spectrometry improves the sensitivity of MS, thus permitting the detection of species present in low concentration. FAEEs are metabolites of ethanol. They are formed by nonoxidative metabolization of ethanol. FAEEs accumulate in various tissues. Ethanol can easily penetrate the placenta and results in the formation and deposition of FAEEs in fetal tissues including meconium. Therefore, FAEEs may be used as biomarkers for heavy alcohol consumption during pregnancy. In the first chapter of this dissertation (chapter 4), FAEEs were extracted from meconium and analyzed by LC-MS to determne the amount of ethyl linoleate, ethyl oleate, and ethyl palmitate. Among the fifty samples run, two were from mothers who had admitted alcohol consumption during pregnancy and those samples were found to contain high amounts of ethyl linoleate and ethyl palmitate. In the follow chapter of this dissertation (chapter 5), tandem mass spectrometry analyses were performed on PEO oligomers to elucidate their fragmentation pathways. These mechanisms derived the structural elucidation of the PEO copolymers analyzed by LC-MS[superscript n] in subsequent studies, as itemized below. In chapter 6, different chain lengths of a PEO-poly(propylene oxide) (PPO) triblock and a PEO-PPO random copolymer was separated and identified by LC-MS[superscript n]. Separation of the oligomers were based on their propylene oxide (PO) content. Oligomers with higher PO content had longer retention times. A putative PEO-poly(dimethylsiloxane) block copolymer was also investigated; in this case, unexpected minor byproducts/starting materials which could not be observed by MS were detected and identified using the LC-MS[superscript n] technique. Chapter 7 focuses on the LC-MS[superscript n] characterization of a commercial surfactant, Polysorbate 85. It is composed of many species with different degrees of esterification. Some of those species have identical nominal masses which complicates their characterization by MS. Therefore, a separation technique is needed prior to MS analysis. Reverse phase LC separated the oligomers based on their hydrophilicity/hydrophobicity. In addition, LC-MS2 experiments unveiled the esterification degree of the oligomers. A novel technique, IMMS, was also employed for characterization of the constituents of Polysorbate 85. IMMS disperses ions according to their collision cross sections and charge states. Oligomers with a different number of ester moieties could be separated and identified. Finally, Chapter 8 reports how IMMS was used to disperse and characterize linear and cyclic poly(butylene adipate) oligomers. The separation of the oligomers was based on their charge states. IMMS improved the sensitivity of MS and permitted the detection of +3 and +4 charged ions which were undetectable in the single-stage mass spectrum."--Abstract.