Essentially Lipids : Analytical methods for the characterization of lipid materials

Abstract: This thesis describes analytical methods for chromatographic characterizations of lipids in biological and technical systems.Lipids are a group of compounds with a central role in all known forms of life. In addition to the biological roles, lipids are also components in many products of our daily usage. The application areas include food, pharma, cosmetics, biofuels, etc.Analytical characterization of lipids is challenging since a typical lipid extract often contains several hundred unique compounds which also could vary significantly in chemical properties. Separation is in many cases crucial for identification and quantification of individual lipids and here high performance liquid chromatography (HPLC) is regarded as the technique of first choice today.In the present work, methodologies for both normal phase (NP) and reversed phase (RP) HPLC are presented. The focus has been to develop methods that are fast, have low analytical complexity and are compatible with several detection systems. Cyanopropyl coated silica was evaluated as stationary phase for NP-HPLC with the aim to separate all the lipid classes in common lipid extracts. The analytes were eluted with a binary mobile phase system based on hexane, toluene and methanol which yielded in a total runtime of 30 minutes. In a subsequent study, additional stationary phases for NP-HPLC were evaluated for online sample cleanup of polycyclic aromatic hydrocarbons (PAHs) in lipid matrixes. In the demonstrated methodology for RP-HPLC, a binary system consisting of methanol/water was utilized with phenylpropyl coated silica to elute all tested lipid classes in 30 minutes.The methodologies were compatible with various detection techniques including evaporative light scattering detection (ELSD), charged aerosol detection (CAD) as well as electrospray mass spectrometry (ESI-MS) and were applied to characterize lipid materials of both biological and technical nature.