2.1. Instrumentation
GC–MS analysis was performed using an Agilent Technologies
(Santa Clara, CA) 7890A gas chromatograph and an Agilent 7683B
auto injector coupled with a 5975C VL Agilent mass selective
detector. The mass spectral scan rate was 2.86 scans/s. The GC was
operated in splitless mode with a helium (grade 5) flow rate of
0.7 mL/min and the column head pressure was 10 psi. The MS was
operated in the electron impact (EI) mode using an ionization
voltage of 70 eV and a source temperature of 230 8C. The GC
injector was maintained at 250 8C and the transfer line at 280 8C.
GC–MS chromatographic separations were carried out on a
column (30 m 0.25 mm i.d.) coated with 0.50 mm film of 50%
phenyl–50% methyl polysiloxane (Rxi-50) purchased from Restek
Corporation (Bellefonte, PA). The separations of the ten studied
compounds were performed using a temperature program consisting
of an initial hold at 70 8C for 1.0 min, ramped up to 250 8C at a
rate of 30 8C/min followed by a hold at 250 8C for 15 min.