GC–MS was carried out to identify headspace volatiles and
to possibly detect any pattern of variation among samples.
A Varian 3800 GC system (Varian Chromatography
Systems, Walnut Creek, CA), equipped with a flame
ionisation detector was used to perform the analysis. The
system was coupled to a Star chromatography software
system (v. 5.0; Varian Chromatography Systems). A fused
silica capillary column (30 m×0.25 mm i.d.; Alltech
Associates Inc., Deerfield, IL) coated with a 0.25-μm layer
of 5% phenyl and 95% PDMS (AT-5) was used. Helium was
used as the carrier gas. Thermal desorption of the compounds
took place in the GC injection port, equipped with a 0.75 mm
i.d. splitless glass liner, at 250 °C for 5 min in splitless mode.
The split valve was then opened (1:50) and the fibre remained
in the injection port for 1 min. The detector was operated at
250 °C. The oven temperature was programmed to range
from 50 °C (maintained for 3 min) to 250 °C at a rate of
5 °C/min. The final temperature was maintained for 15 min.
The mass range studied was m/z 40−650. Compounds were
quantified or identified by the use of authenticated standards
and by matching their mass spectra with the data stored in
the NIST library of standard compounds.