Analysis of the oil
The oil sample was analyzed by using an Agilent 6890 gas chromatograph equipped with an
Agilent mass spectrometric detector, with a direct capillary interface and fused silica
capillary column HP-5MS (30 m × 0.32 mm, 0.25 µm film thickness). The oil sample was
injected under the following conditions: Helium was used as carrier gas at approximately 1.0
mL/min, pulsed splitless mode. The solvent delay was 3 min. and the injection size was 1.0 µl. The mass spectrometric detector was operated in electron impact ionization mode with an
ionizing energy of 70 e.v. scanning from m/z 50 to 500. The ion source temperature was
230°C. The electron multiplier voltage (EM voltage) was maintained 1250 v above auto tune.
The instrument was manually tuned using perfluorotributyl amine (PFTBA). The GC
temperature program was started at 60°C for 2 min, then elevated to 280°C at the rate of
8°C/min.; the injector and detector temperatures were set at 300°C and 280°C, respectively.
Identification of the oil components’ volatile compounds was based on the calculation of
their retention indices (calculated using n-alkanes), as well as by co-injection of authentic