Title: Dual Parallel Liquid Chromatography with Dual Mass Spectrometry (LC2/MS2) for a Total Lipid Analysis Author
Submitted to: Frontiers in Bioscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 11, 2007
Publication Date: January 1, 2008
Citation: Byrdwell, W.C. 2008. Dual parallel liquid chromatography with dual mass spectrometry (LC2/MS2) for a total lipid analysis. Frontiers in Bioscience. 13:100-120. Interpretive Summary: Lipidomics is the study of the full range of fats, lipids and related materials in a sample. Some lipids, such as phospholipids, are polar and somewhat hydrophilic, while others are non-polar and hydrophobic. Because of their different polarities, lipids have been very difficult to analyze all together using a single, comprehensive analysis method. Presented here is a description of an approach to lipidomics analysis using two separation techniques that use separation columns with opposite polarities that are joined together by an electronic switching valve, so that all lipids, both polar and non-polar can be separated using a single, unified analysis method. The non-polar lipids move down one column quickly and are diverted to a second column, where they are separated using liquid chromatography for non-polar molecules. At the same time, the polar lipids are not diverted, and are separated on a liquid chromatography column designed for polar molecules. The molecules from both columns are identified by their masses, as they pass into a mass spectrometer. This arrangement of two liquid chromatography separation systems and two mass spectrometers for detection of all polar and non-polar lipids was demonstrated by performing a total lipid analysis of a fish filet and of a bovine brain extract.
Technical Abstract: 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 filet 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.