Accurate LC-MS/MS Analysis of Diacylglycerols in Human Plasma with Eliminating Matrix Effect by Phospholipids Using Fluorous Biphasic Extraction

We developed an accurate method for determining diacylglycerols (DAGs) in human plasma using a fluorous biphasic liquid-liquid extraction method, followed by liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis. The lipid mixture in the plasma was first extracted with chloroform by using the Bligh-Dyer method. The resulting solution was subjected to fluorous biphasic liquid-liquid extraction to remove phospholipids, which are known to cause matrix effects during the LC-MS/MS analysis. In this method, phospholipids in a lipid mixture solution (nonfluorous solvent) were selectively extracted to tetradecafluorohexane (fluorous solvent) via the specificity of fluorous affinity by forming a complex with a perfluoro-polyether-carboxylic acid-lanthanum(III) salt. The remaining DAGs in the nonfluorous solvent could be directly injected into the LC system through the positive electrospray ionization-MS/MS mode. The removal rate of the phospholipids through the fluorous biphasic extraction was more than 99.9%; thus, the matrix-effect-eliminating analysis of DAGs in human plasma with LC-MS/MS was enabled. Furthermore, the applicability of this method and the possibility of using DAGs as biomarkers were evaluated by applying this method to human plasma samples obtained from major depressive disorder as a related disease.