2.4. Extraction and chromatographic analysis of fatty acids
Lipid extraction was performed according to Hara and Radin (1978) and transesterification of the FA according to Christie (1982). The FA methyl esters (FAME) in hexane were then injected (1 mL) into a gas chromatograph (PerkinElmer e Clarus 500B, The Netherlands) equipped with a flame ionization detector (FID) and a PTV injection port used in the split mode with a split vent flow of 100 mL/min and a split ratio of 1/25. The oven temperature program was initially set at 100 C for the first minute, then increased at a rate of 2.5 C/min to 240 C (remaining for 20 min). Hydrogen was the carrier gas at flow rate of 45 mL/min, injector temperature of 245 C and detector temperature of 270 C. The separation of the FAME was performed with a WCOT fused-silica CPWAX 58 capillary column (Varian Middelburg, The Netherlands) with a length of 50 m, inner diameter of 0.25 mm and film thickness of 0.20 mm