Free faty acids were quantified with LC-MS/MS method developed for a Shimadzu Nexera XR UHPLC system (Shimadzu Scientific Instruments, Columbia, MD). An isocratic method was developed with 95:5:0.1 water: acetonitrile: formic acid as the mobile phase (flow rate-0.6 mL/min). A Phenomenex Kinetex 2.6-micron EVO C18 column (50 X 2.1 mm) was used to partially separate amino acids. The sample injection volume was 2 µL. For LC-MS/MS detection, an electrospray ionization source in positive ion mode was selected with the following parameters: temperature-250 °C; nebulizing gas flow-3.00 L/min; heat block-450°C; and drying gas flow-20 L/min. Data were processed with Shimadzu LabSolutions software. The calibration curve was prepared with standards at a concentration of 0.25 ng/mL to 250 ng/mL. 100 µL of each sample was dried down under a steady stream of nitrogen and reconstituted with 100 µL of the mobile phase.