Characterization of unsaturated lipids with high structural specificity by coupling epoxidation with tandem mass spectrometry

Comprehensive characterization of lipid structures is of significance, as they play a key role in numerous biological processes. Mass spectrometry (MS) emerges as a preferred tool for lipid analysis, providing good performance in sensitivity and accuracy. However, characterization of unsaturated lipids still has certain difficulties due to structural diversity. In this work, combining epoxidation and tandem MS was developed for unsaturated lipids analysis with high structural specificity. By using the proposed method, it could simultaneously produce high-abundance diagnostic ions specific to lipid C=C locations and sn-positions, facilitating lipid isomers identification. Determining C=C location and sn-position isomers of lipid in a single spectrum can be achieved, which is valuable for discovery of great structural diversity. The capability of this approach in characterizing unsaturated lipids at high structural level has been illustrated with different standards including a lipid extract from complex biological sample. The relative quantitation capability of C=C location and sn-position isomers was also demonstrated based on diagnostic ion intensities.