1-stearoyl-2-arachidonoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt) (SAPG) is a sodium salt of glycerophospholipid, with substitution of stearic acid, arachidonic acid and phospho-rac-(1-glycerol) at the sn-1, sn-2 and sn-3 positions respectively, in the glycerol backbone. It has been used as a standard in liquid chromatography tandem mass spectrometry (LC-MS/MS) method for lipid quantification.