Development of IsoK-PE LC/MS/MS assay. A: CID spectrum of m/z 1032.7 ion. B: Interpretation of CID spectrum. C: MRM ion chromatographs from LC/MS/MS analysis of IsoK-PE preparation for C34:1 PE and IsoK-34:1 PE pyrrole. IsoK, γ-ketoaldehyde isomer. CID, collision induced disassociation; IsoK, γ-ketoaldehyde isomer; MRM, multiple reaction monitoring; PE, phosphatidylethanolamine.