Mass Spectrometry for Analysis of Glycerolipids

Acylglycerols (AGs), or glycerides (GLs), are active biomolecules in their own right but also act as the foundational building blocks for multiple classes of the most common lipids. Because of this, most of the fragments observed from mass spectrometry (MS) of monoglycerides (MGs), diglycerides (DGs), and triglycerides (TGs) are common to multiple classes of lipids. Therefore, knowledge of the mass spectral patterns of GLs informs analysis of a variety of lipid classes, especially phospholipids (PLs). In this chapter, we discuss the analysis of AGs using a variety of MS techniques. MGs and DGs are small enough and have readily available derivation sites, so these are commonly derivatized and analyzed by gas chromatography (GC). GC is a more mature field than liquid chromatography (LC)-MS, so many of the original fragment identities and mechanisms were elucidated using GC-MS techniques and then later were re-assessed or confirmed using LC-MS. This chapter describes the best derivatives for structural elucidation and the best adducts for LC-MS to obtain maximum structural information. Emphasis is on newer atmospheric pressure ionization (API) methods. The latest trends in lipidomics and quantitative analysis are discussed, as well as the need for standardization to minimize the amount of unconfirmed or unsupported lipid assignments made from automated software. The future for AG analysis by mass spectrometry is surely bright, but there are steps that need to be taken to facilitate the most beneficial outcomes from the ongoing lipidomic analysis.