Chapter 13 LC/MS of Natural Glycerolipids, Sterols and Steryl Esters

Abstract

This chapter discusses the instrumental and analytical problems in liquid chromatography–mass spectrometry (LC/MS) and of the potential of the combined system for practical analysis of glycerolipids, sterols, and steryl esters. The bulk of the applications are performed with the commercially available direct liquid inlet and moving belt interfaces and conventional reversed phase high pressure liquid chromatography (HPLC) columns. Although the direct liquid inlet interface allows the analysis of only one percent of the column effluent, it does not create a problem when sufficiently large samples of lipids are available. Similarly, the theoretical disadvantage of being limited to special solvents and chemical ionization does not emerge as a handicap, because the lipid species are best detected in the chemical ionization mode that also provides adequate fragmentation of the molecules for structural studies. For this reason, the moving belt interface thatallows both electron impact and chemical ionization mass spectrometry holds little advantage over the direct liquid inlet system for lipid work. There is a need, however, for reducing the sample size requirements and this may be possible by the use of capillary HPLC columns.