2.5. Determination of FAS
Measurement of FAs was carried out using GC–MS coupling. Fatty acids were transformed to their methyl esters (FAME) following the method of Hartman and Lago (1973). The FAME samples were injected into DB-5 semi-polar column (50 m; i.d.:0.25 mm). The column temperature was programmed to remain isothermal at 90 _C for 8 min, after which the temperature was increased at a rate of 10 _C per minute to 180 _C and stayed for 35 min. The volatiles were identified using a FINNIGAN TRACE2000
gas chromatograph interfaced with a FINNIGAN AUTOMASS TRACE2000 mass selective detector. Electron impact mass spectral analysis was carried at ionization energy of 70 eV. The structural
arrangements of the volatiles were established by comparing mass spectra of separated compounds with NIST/EPA/NIH MS database v 5.0 using a microcomputer system.