Ultra high performance liquid chromatography–mass spectrometric analysis of oxidized free fatty acids and acylglycerols

Abstract

A fast ultra high performance liquid chromatography (UHPLC)-electrospray ionization (ESI)-mass spectrometric (MS) method was developed for simultaneous analysis of free fatty acids (FFAs), monoacylglycerols (MAG), diacylglycerols (DAG), triacylglycerols (TAG), and their oxidized equivalents. Effect of elevated column temperature was studied in order to optimize the chromatography of closely eluting peaks and to reduce high back pressure formed in UHPLC. The elevated temperature enabled high flow rate, better mass transfer, and therefore more narrow peaks and better separation of the analytes. The new method was applied to the analysis of total lipid extracts of lipolysis samples prepared by an artificial digestion model in order to investigate oxidized lipids and changes in their profiles in the chyme. Over 150 compounds were identified from the extracts. The UHPLC-ESI-MS method was proved to be fast, highly selective, and sensitive. Compared to a previously used high performance LC-ESI-MS method, the new UHPLC-ESI-MS method was over five times faster and consumed one tenth of the solvents while producing comparable quantitative results.Practical applications: Edible oils and fats contain mainly TAGs, the lipolysis of which produces FFAs and MAGs with minor DAG components. These compounds are susceptible to oxidation in the stomach, and therefore the analysis of the oxidation products is important. Fast determination of FFAs and acylglycerols is also important in quality control of biodiesel. Our new method enables accurate and sensitive determination of different molecular species present in digested and processed samples with minimal sample preparation requirements. In this respect, the new method is applicable to large scale and fast screening of biological samples for lipidomic and metabolomic studies.

A Simple Quantitative Approach for the Determination of Long and Medium Chain Lipids in Bio-relevant Matrices by High Performance Liquid Chromatography with Refractive Index Detection

“…However, LC-MS has not found extensive application in lipid analysis, mainly as a consequence of high equipment costs and limited availability and also as a result of variability in molecular ion fragmentation patterns (33,34). Furthermore, carboxylcontaining analytes require derivatisation to increase their ionisation efficiency in HPLC-MS analyses (24).…”

Effects of Antioxidants on Rapeseed Oil Oxidation in an Artificial Digestion Model Analyzed by UHPLC–ESI–MS

“…Chemically and thermally oxidized rapeseed oils were used from previous experiments . 12-Hydroxyoctadecanoic acid (>98%) was obtained from Larodan Fine Chemicals AB.…”

“…The gradient method developed was based on our earlier UHPLC–ESI–MS method for total lipid analysis . The solvent gradient was adjusted for the new column type (previously Waters BEH C18, 2.1 × 100 mm, 1.7 μm particle size) and the different solvent B.…”

“…Specialized liquid chromatography–mass spectrometric methods may provide better answers to the questions of the formation of oxidized lipids than generic colorimetric assays. , Suomela et al have employed high performance liquid chromatography–electrospray ionization–mass spectrometry (HPLC–ESI–MS) in the quantitative analysis of oxidized triacylglycerols in lipoproteins and intestinal epithelial cells. , Recently, Tarvainen et al have described an ultrahigh performance liquid chromatography (UHPLC)–ESI–MS method, which enables accurate and sensitive determination of oxidized and nonoxidized molecular species of lipids present in digested and processed samples with minimal sample preparation . In the present study, this method has been further improved by including lithium ions as ionization enhancers in ESI–MS.…”

Novel method based on fourier transform infrared spectroscopy for determining fat acidity of cereal products

“…Determination of FA value is prone to titration error in case of strongly coloured samples and requires large sample sizes and solvent volumes. Thus, several alternative techniques, including flow injection, [3][4][5] pH-metry, [6] gas chromatography, and high-performance liquid chromatography, [7][8][9] have been employed in recent years to avoid these drawbacks. Most methods for lipid extraction from food are labour intensive, and large amounts of hexane are needed.…”