Summary
The analysis of lipids is technically very challenging, not only due to the large number of various classes of compounds provided by the cell, but also due to the enormous heterogeneity of these various classes. Especially plants with their large pigment content and their high degree of polyunsaturated acyl residues make lipid analysis in this system even more complicated. Due to this high complexity, more and more sophisticated large-scale lipid-analysis systems have been developed, intended for the analysis of the so-called “lipidome”, that is the entire lipid composition of a cell or a whole organism. These methods often consist of various building blocks, which show interlaced modularity. The two basic elements of a lipidomic analysis are an efficient extraction procedure and a sensitive detection system. In addition to these two basic elements, depending on the analytical question, additional separation and sample purification procedures can be introduced. Mass spectrometry (MS)-based techniques are at the forefront of lipidomic analysis. These extremely sensitive and accurate detection methods are applied to investigate all kinds of lipid. Their application, in combination with various plant-specific techniques of extraction and separation, including solid-phase extraction, thin-layer chromatography and high-performance liquid chromatography are presented in this chapter. Most of the MS-based technologies for lipid profiling of partially polar lipids rely on electrospray ionization, while more apolar lipids, like sterols, can be ionized by techniques, such as atmospheric pressure chemical ionization. A number of various applications employing these mass spectrometric methods will be discussed. Finally combinations of various separation and detection technologies, so-called hyphenated approaches, such as high-performance liquid chromatography coupled to mass spectrometry or gas chromatography coupled to time of flight or quad-rupole mass spectrometry, are introduced and their suitability for lipid analysis are discussed.