Spectroscopy and spectrometry of lipids — Part 1

For a collection of articles on spectroscopy and spectrometry of lipids to be comprehensive, there is a requirement for a wide range of instrumentation and applications to be considered. In this dossier, the aim is to include as many aspects as possible that are relevant to modern approaches in lipid analysis. It is hoped that the articles will show how enormous advances have been made, and are continuing to be made, in this area. The range of techniques includes infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), ultraviolet (UV) spectroscopy and electron spin resonance (ESR) spectroscopy. IR spectroscopy can be subdivided further into mid- and near-infrared and Raman spectroscopy, and the former may be coupled to gas chromatography (GC). NMR spectroscopy encompasses high resolution (further split into 1 H, 13 C and 31 P) and time-domain. MS can be subdivided according to the type of ionisation (e.g. electron impact, chemical ionisation, fast atom bombardment) or separation technique (e.g. GC, liquid chromatography) to which it is coupled, but is more conveniently considered according to the type of lipid (fatty acid, triacylglycerol, complex polar lipid) to be analysed. Analysis of stable isotopes in fatty acids involves a highly specialised application of MS. There is a host of applications ranging from the measurement of broad quality control parameters to highly specific determinations for research purposes, and includes both qualitative and quantitative information. Quality control applications include chemical parameters such as peroxide value by IR (as a possible replacement for more timeconsuming traditional methods) and physical parameters such as droplet size distribution by time-domain NMR. Structural determinations of fatty acids and lipids by the various MS methods tend to be targeted towards specific research objectives.