Submitted to: Experimental Biology and Medicine
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/2/2008
Publication Date: 2/13/2009
Citation: Yu, S., Li, Q., Badger, T.M., Fang, N. 2009. Quantitative analysis of polar lipids in the nanoliter level of rat serum by liquid chromatography/mass spectrometry/mass spectrometry. Experimental Biology and Medicine. 234(2):157-163. Interpretive Summary: Lipids are one of the most important classes of compounds in the body. They have both structural and functional roles in both health and disease. Measurements of the levels and types of lipids are essential to the process of diagnosis of diseases. We have developed a new method to identify and quantitate all classes of lipids in very small amounts of serum. This method reduces losses of previous methods and allows the analyses of more than 50 lysophospholipds and 30 free fatty acids. This approach should be perfectly suited for precise quantification of a specific serum component by adding its isotope standard to the serum before extraction.
Technical Abstract: Polar lipids in serum, including lysophospholipids (LPLs) and free fatty acids (FFAs), have a broad range of biological activities and require a suitable method for their quantitative analysis. Conventional methods use multistep procedures to simultaneously purify and analyze polar lipids and non-polar lipids in serum. However, the methods could result in inaccurate quantifications of polar and/or non-polar lipids because compounds with different polarities have different behaviors in solvent extraction and mass spectrometric ionization. In this study, a method designed to analyze polar lipids in serum based on the polarities of LPLs and FFAs. The method consisted of extraction without filtration and analysis of the crude extract without multistep purification. Fifty LPLs and thirty-two FFAs were detected in rat serum. The concentrations of LPLs (1272.1 µmole/L in female and 999.8 µmole/L in male) and FFAs (1910.9 µmole/L in female and 1651.4 µmole/L in male) were determined. Peak areas of MS ion in Extract Ion Chromatogram (EIC) were used for the quantification in this study, and the approach should be perfectly suitable for precise quantification of a specific serum component by adding its isotope standard to the serum before extraction.