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.