Improved LC-MS Method for the Determination of Fatty Acids in Red Blood Cells by LC-Orbitrap MS

We report a new method for fast and sensitive analyses of biologically relevant, fatty acid (FAS) in red blood cells (RBC) by liquid chromatography mass spectrometry (LC-MS). A new chemical derivatization approach was developed forming picolylamides from FAs in a quantitative reaction. Fourteen derivatized FA standards, including saturated and unsaturated FAs from C14 to C22, were efficiently separated within 15 min. In addition,, the use of a recently introduced benchtop orbitrap mass spectrometer under positive electrospray ionization (ESI) full Scan mode showed a 2-10-fold improvement in Sensitivity compared with a conventional tandem MS method, with a limit of detection in the low femtomole range for saturated and unsaturated FAs. The developed method was applied to determine FA concentrations in RBC with intra- and interday coefficients of variation below 10%.