The GC-MS analysis was done in a HP-6890 Series GC System /
HP-5973 Mass Selective Detector equipped with a HP-5ms fused
silica capillary column with a (5% phenyl)-methylpolysiloxane
stationary phase (30 m long × 0.25 mm i.d., film thickness 0.25 m).
The temperature of the column was programmed at 50°C for the
first 2 min and was then increased 3°C per minute up to the isothermal
at 250°C (being held for 30 min). The injector and detector
temperatures were maintained at 250°C. The carrier gas was
helium at a flow rate of 1.0 ml/min. The quadrupole mass spectrometer
was scanned over the range 30–350 amu at 3 scan s
-1
, with
an ionizing voltage of 70 eV, ionic source temperature of 230°C,
split ratio of 1:20 and an ionization current of 150 A. The oil components
were identified by retention times (Davies, 1990; Adams,
2001), retention indices, co-injection of the standard and compareson
with a homologous series of National Institute of Standards and
Technology (NIST) V.2.0 GC–MS library. Relative amount of the
individual component was obtained electronically by FID peak-area
normalization without the use of correction factors.