Post-column infused internal standard assisted lipidomics profiling strategy and its application on phosphatidylcholine research.

Various lipidomics studies have revealed the potential of using phospholipids as disease biomarkers for conditions such as Alzheimer's disease, cancer, and sepsis. Establishing accurate quantification methods for targeted phospholipid analysis is important for making these potential markers more clinically relevant. Although a stable isotope labelled-internal standard method can provide good quantification accuracy for endogenous metabolite quantification, there are limited isotope labelled phosphatidylcholines (PCs) commercially available. For this reason, this study proposed a postcolumn infused-internal standard (PCI-IS) method for the accurate quantification of PCs. To demonstrate the quantification accuracy of the PCI-IS method combined with the matrix normalization factor (MNF), 2 LPCs and 6 PCs have been quantified in the human plasma specimens, and the results showed that the PCI-IS combined with MNF method can provide quantification results as accurate as those of the standard addition method (SAM) but without the need for the labor-intensive SAM procedure. We additionally applied the PCI-IS method for improving the PC profiling accuracy, and the results indicated that the biased estimation of the PC composition caused by the MEs can be resolved by PCI-IS correction. Finally, the method was applied to investigate drug resistance in lung cancer cells. Decreased levels of PCs in drug resistant cells disclose the potential role of PCs in drug resistance. We anticipate that the PCI-IS strategy could help quantitative lipidomics move forward and further contribute to various clinical and biomedical studies.