Used as an isotopically labeled internal standard in mass spectrometry-based lipidomics research. Enables accurate quantification of phospholipids in complex biological samples by providing a reference with similar chemical properties but distinct mass due to deuterium labeling. Commonly applied in studies of cell membranes, metabolic pathways, and disease biomarkers where precise lipid profiling is required. Its stable isotope label (d31) minimizes interference from endogenous lipids, improving measurement accuracy and reproducibility.