Applications of Direct Infusion Mass Spectrometry in Lipidomics

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http://urn.fi/URN:NBN:fi-fe2017112252177
Title: Applications of Direct Infusion Mass Spectrometry in Lipidomics
Author: Ekholm, Niko
Contributor: University of Helsinki, Faculty of Science, Department of Chemistry
Publisher: Helsingfors universitet
Date: 2016
Language: eng
URI: http://urn.fi/URN:NBN:fi-fe2017112252177
http://hdl.handle.net/10138/230511
Thesis level: master's thesis
Discipline: Analytical Chemistry
Analyyttinen kemia
Analytisk kemi
Abstract: Lipids are currently one of the most studied biological compounds in addition to proteins. The research field of lipidomics covers identification and quantification of lipid components in various biological systems. Lipidomics reveals answers to connection between lipid metabolism and lipid related diseases and malfunctions. Lipidomics belongs in the general group of metabolomics and is probably currently fastest growing field of so-called omic sciences. Mass spectrometric (MS) techniques have made probably highest impact on lipidomics and are gaining more and more popularity. MS has some major advantages over other conventional detection techniques. This is due to that MS allows identification and detection in lower concentration levels as well as analysis of intact lipid compounds. In the literature section, direct infusion mass spectrometric (DIMS) methods are studied from the viewpoint of lipid analysis. When direct infusion mass spectrometry is applied, the analysis is carried out by infusing the sample mixture directly into mass spectrometer without chromatographic separation and with very little sample preparation. Basic requirement for direct infusion mass spectrometric analysis is the utilization of tandem mass spectrometer in order to be measure analytes from the complex mixtures. There are two approaches in direct infusion mass spectrometry: targeted and global. DIMS is especially suitable for quick profiling and qualitative analysis of lipids, but also for quantitative analysis. The experimental part was carried out at the Neste Corporation R&D in Porvoo, Finland. Global approach for direct infusion ESI-MS/MS was studied to develop semi-quantitative profiling method for the different renewable diesel (NExBTL) feedstocks. The measured lipid classes were monoglycerides (MAG), diglycerides (DAG), triglycerides (TAG), ethyl esters (EE), wax esters (WE) and steryl esters (SE). Analytes were measured as ammonium adducts [M+NH4]+. DAG and TAG were measured with neutral loss scan (NL) and all the other classes with multiple reaction monitoring (MRM). The profiling method was developed to evaluate broader range of intact lipids for the NExBTL-process feedstock. Additional analytical methods are needed since the problems associated with the analysis are increased with the use of recycled lower price bio-oils or side streams as a feedstock, which is the upcoming trend in the field of biofuels. Study mainly consisted of fundamental work, including testing of infusion solutions, target ion selection for the mass spectrometric quantitation, mass spectrometric parameter optimization and generation of text database file, which was used as analyte database for the MRM-measured (MAG, EE, WE, SE) analytes. In addition to these, relative response factors and linearity were determined. Before the actual samples, also method performance was tested by artificial sample. Finally, analysis method was used to analyse several real samples. The results were compared to those obtained with the existing older GPC/SEC analysis method. Method showed good functionality in the quantitative or semi-quantitative level and it was taken into routine use in the R&D laboratory.


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