Direct ultrasound-assisted methylation of fatty acids in serum for free fatty acid determinations

A method for simultaneous determination of 16 free fatty acids (FFAs) in serum is described. The method involves conversion of FFAs to fatty acid methyl esters (FAMEs) using the heat of ultrasonic waves followed by gas chromatography and mass spectrometry (GC-MS) analysis. Optimum levels of the variables affecting the yield of FAMEs were investigated. The results indicate that the optimal levels are 55 degrees C, 60 W, 10 % H2SO4/CH3OH, and 50 min. Recoveries ranged from 85.32 % to 112.11 %, with a detection limit ranging from 0.03 to 0.08 g mL-1. The linearity, using the linear correlation coefficient, was higher than 0.9914.