Analyses were performed by a Thermo Finnigan gas chromatograph
(GC) equipped with a DB-5MS column (Agilent Technologies,
USA) (30 m, 0.25 mm, film thickness 0.25 mm) and a mass spectrometry
detector (MS). Helium was used as the carrier gas with a
flow rate of 1 ml min1
. The oven temperature was programmed to
start at 40 C (held for 4 min), increase to 250 C at 15 C min1 and
then to hold at 250 C for 2 min. The injector and auxiliary temperatures
were 250 C. Injections were performed in split mode
with a 1:10 ratio. MS detection was performed in the mass range of
50e450 atomic mass unit (amu) at 4 scans s1
. The solvent delay
was 6 min.