Fig. 1

The brief workflow of mass spectrometry-based lipidomics. Yellow boxes illustrate the representative lipid extraction methods currently been widely used [104]. The Folch method [105] is ideal for large samples (> 0.1 g of tissue), while B&D [106] is more appropriate for smaller samples (< 50 mg) [104, 107]. MTBE method [108] improves workflow automation by separating lipids into an upper organic phase, but it risks aqueous-phase contamination. BUME method [109] reduces contamination with a butanol/methanol mixture but complicates lipid collection due to the volatility of butanol. Green boxes illustrate the major lipidomic methodologies. Direct infusion-MS, also known as shotgun lipidomics [110], uses direct infusion of lipid extracts into a mass spectrometer without pre-separation. This technique minimizes lipid aggregation and is highly accurate for quantification. Chromatography-MS acquires a pre-separation of lipids before being introduced into a mass spectrometer. This includes NPLC, normal phase liquid chromatography, ideal for separating polar lipids [111]; RPLC, reversed phase liquid chromatography, resolves lipid species based on the hydrophobicity of lipids [112]; HILIC, hydrophilic interaction liquid chromatography, bridges the gap for polar lipids that RPLC struggles to retain [113]. MS imaging, mass spectrometry imaging, allows the visualization of lipid molecules directly in tissue sections without extraction or labeling, enabling insight into lipid localization in disease-affected areas. Purple boxes illustrate the techniques used during data acquisition. Ionization methods are listed in box (a) ESI [114], electrospray ionization, creates ions by applying high voltage to a liquid to form an aerosol. Atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) [115] are ideal for ionizing less polar molecules. MALDI [116], often paired with time-of-flight (TOF) MS, provides spatial information on lipid location. DESI [117] allows real-time imaging with minimal sample preparation, while SIMS [118] offers detailed surface analysis ideal for studying lipid membrane [119]. Mass spectrometry approaches are listed in box (b) Tandem MS [120], uses mass selection (MS1) to identify molecular mass and applies a second round of MS (MS2) to deduce lipid structures. High mass accuracy MS [121] provides precise identification of lipids based on accurate mass. Multidimensional MS (MDMS) selectively ionizes lipid categories using different ionization conditions and matrix modifiers (e.g., intrasource separation [122])