Online Extraction Followed by LC-MS/MS Analysis of Lipids in Natural Samples: A Proof-of-Concept Profiling Lecithin in Seeds

Sample preparation is usually a complex and time-consuming procedure, which can directly affect the quality of the analysis. Recent efforts have been made to establish analytical methods involving minimal sample preparation, automatized and performed online with the analytical techniques. Online Extraction coupled with Liquid Chromatography-Mass Spectrometry (OLE-LC-MS) allows a fully connected extraction, separation, and analysis system. In this work, the lecithin profile was investigated in commercial sunflower, almonds, peanuts, and pistachio seeds to demonstrate that the concept of extraction, followed by the online analysis of the extract, could be applied to analyze this class of analytes in such complex solid matrices without a prior off-line solvent extraction step. The extraction phase gradient method was optimized. Two different analytical columns were explored, one being a conventional C18 (50 x 2.1 mm, 1.7 mu m SPP) and the other a novel self-packed SIGO-C18ec (100 x 0.5, 5 mu m FPP), which resulted in better separation. The analysis repeatability was investigated, and suggestions to improve it were pointed out. A characteristic ion with a m/z of 184, related to lysophosphatidylcholine structure, was used to identify the lecithin compounds. The temperature effect on the chromatograms was also explored. In short, it was found that the OLE-LC-MS approach is suitable for the analysis of lecithin compounds in seeds, being a promising alternative for lipidomics approaches in the near future.