The lipid composition (lipidome) in biological samples is extremely complex, having diverse biofunctions. Quantifying lipidomes with high coverage is vital to understand such functions but challenging due to their levels spanning several orders of magnitude, limited available standards, and poor chromatographic performances for many acidic lipids such as sphingosine-1-phosphate, phosphatidylserines, and phosphatidic acids. Here, we report a reliable method for high-coverage quantitative lipidomics using ultrahigh-performance liquid chromatography and tandem mass spectrometry (UHPLC-MS/MS). By using both pH and ammonium gradients in elution, all lipids, especially acidic ones, had obviously improved LC separation. By using 267 lipid standards in 49 subclasses, we also established quantitative structure-retention relationship models to predict the retention time (tR) with good accuracy (ΔtR E. coli, Arabidopsis leaves, mouse liver tissue, and feces. This offers a high-coverage quantitative method for understanding molecular phenotypes associated with lipid functions in physiology and pathophysiology.
Chen et al. (Tue,) studied this question.