2.5. GC-MS Analysis of Fatty Acids

Fatty acid methyl esters (FAMEs) were obtained from total lipids using the acid-catalyzed transesterification procedure described by Christie [28]. The FAMEs were analyzed by gas chromatography-mass spectrometry (GC-MS) using a PerkinElmer Clarus 600 T GC-MS (PerkinElmer, Inc., Shelton, CT, USA) fitted with a Supelcowax 10 (60 m × 0.25 mm i.d., 0.25 μm film thickness; Supelco Inc., Bellefonte, PA, USA) capillary column, using helium as a carrier gas (flow rate of 0.8 mL/min) [29]. The temperature program for the column was: initial temperature, 140 °C, increase by 7 °C/min to 220 °C, and hold for 23 min. The injection volume was 0.5 μL (split ratio of 1:24) and the injector was set at 210 °C. The MS operating conditions were as follows: electron impact ionization voltage 70 eV (E.I., positive ion electron impact mode), trap current of 100 μA, source temperature of 150 °C, scan rate 0.14 scan/s and scanned mass range 22–395 m/z. The identification of FAMEs was achieved by comparing their retention times with those of known standards (37 component FAME Mix, SUPELCO # 47885-U) and the resulting mass spectra to those in our database (NIST MS Search 2.0). The compositions of fatty acids in the studied lipids were expressed as percentages (%) of the total FAME peak areas. All experiments were performed in triplicate.