Analysis of Fatty Acid in Biological Samples Using Liquid Chromatography–Quadrupole-Orbitrap Mass Spectrometry Under Parallel Reaction Monitoring Mode

Fatty acids(FAs)are an important class of functional small molecules and participate in a variety of life biological processes.This experiment proposed a liquid chromatography–quadrupole-Qrbitrap mass spectrometry(LC–Q-Orbitrap MS)method to perform FA profiling under parallel reaction monitoring(PRM)acquisition mode.The FA was derivatized by 2-dimethylaminoethylamine(DMED)to increase the ionization e fficiency and provide the characterized fragment pattern.The mass spectra obtained from full scan,multiple ion monitoring(MIM),and PRM were compared.The results showed that the protonated ion of FA+DMED–H2O was detected and the neutral loss of 45.06 Da was observed in the tandem mass spectrum.The PRM method provided the highest selectivity and sensitivity for FA detection with the help of accurate mass weight and specific neutral loss-based fragments.The method validation was performed using the FA standards and pooled quality control serum sample,which showed that the established method had good repeatability,stability,and linearity.Finally,the developed method was successfully applied to analyze the rat serum and brain tissue samples for the drug e ffi-cacy evaluation of gross saponin of Tribulus terrestris L.fruit(GSTTF)against middle cerebral artery occlusion(MCAO)-induced ischemic stroke.This method has extensive practicability and great potential in the detection of FA,especially for the analysis of samples with complex matrices.