ABSTRACT
Part I: Introduction ..................................................................................................18 Magnetic Sector and Electric Sector .............................................................19 Quadrupole Mass Filters and Ion Traps ........................................................19 Interface to High-Pressure Liquid Chromatography (HPLC).......................20 ESI Mechanism..............................................................................................21 Molecular Ion Species ...................................................................................22 Collisional Activation of Lipid Ions ..............................................................25 Data Systems..................................................................................................28
Part II: Electrospray Mass Spectra of Sample Lipids ............................................28 Fatty Acids .....................................................................................................29 Glycerolipids ..................................................................................................31 Glycerophospholipids.....................................................................................34 Sphingolipids..................................................................................................41 Sterols ............................................................................................................45 Isoprenoids .....................................................................................................47 Saccharolipids ................................................................................................51 Polyketides .....................................................................................................51
Conclusion ...............................................................................................................53 Acknowledgments....................................................................................................53 References................................................................................................................53
The analysis of lipid substances by mass spectrometry is almost as old as the technique itself. The inventor of the mass spectrometer, J.J. Thompson, used his new instrument to investigate the positive rays of electricity generated from simple hydrocarbon gases derived from decaying lipids (1). The progress of mass spectrometry was rapid even a century ago, and one of the first biochemical applications involved the use of a magnetic-sector mass spectrometer to help unravel the complexity of steroid biosynthesis, using the newly discovered stable isotope, deuterium (2). However, many of the mass spectrometers used today for the analysis of lipids have evolved from the pioneering thoughts of Wolfgang Paul (3), who devised the quadrupole mass filter and ion trap. Another mass spectrometric technology rapidly being applied to lipid analysis is time-of-flight mass spectrometry. Although each mass separation device has its own strengths and weaknesses, all these instruments separate ions as to their mass-to-charge ratio (m/z), the fundamental unit of mass spectrometry. Often the choice of what type of physical instrument to use is predicated on the mass accuracy desired for the analysis, the ease of collisional activation of ions, the ease of coupling the flowing stream of liquid or gas containing the sample to the mass spectrometer, as well as the ease of operation and, not to the least extent, financial investment in the equipment.
