Dual parallel liquid chromatography with dual mass spectrometry (LC2/MS2) for a total lipid analysis

Total lipid extracts containing both polar and non-polar lipids were separated using two liquid chromatographic systems joined together using a column-switching valve. Detection was accomplished using mass spectrometers attached to each of the two liquid chromatographic systems, for a dual liquid chromatography/dual mass spectrometry (LC2/MS2) arrangement. This experimental approach is demonstrated to be useful to identify many classes of polar and non-polar lipids, and numerous individual molecular species within each class, which is a primary goal of lipidomics. Data are presented from a bovine brain total lipid extract and a sand bream fillet extract as examples. The use of both ESI-MS and APCI-MS are demonstrated for analysis of non-polar lipids, and advantages and shortcomings of each technique are discussed. The two parallel chromatographic separations are compared to lipidomics approaches that employ infusion without chromatography. The data show that the LC2/MS2 is one approach to a comprehensive total lipid analysis that can be performed using only commercially available instruments with no fabrication or modification required. The LC2/MS2 approach represents a uniquely valuable tool for monitoring the amounts of precursors and products of molecules involved in cell signaling processes. The dual liquid chromatography/dual mass spectrometry approach represents one of the most powerful tools for lipidomics analysis reported to date.