2.8. Gas chromatography-mass spectrometry
Essential oil samples were diluted in hexane (5 ml/ml) in autosampler
vials and analyzed using an Agilent 6890/5975 GC-MS
system (Agilent Technologies, Palo Alto, CA), equipped with a HP-
5MS capillary column (30m 0.25 mm inner diameter and film
thickness 0.25 mm). Sample volumes of 1 ml were injected with a
split ratio of 15:1. Injection and interface temperatures were set at
230 C and 250 C, respectively. He was used as carrier gas at a
constant flow rate of 1 ml/min. The column oven was initially
adjusted to 40 C and ramped to 250 C at a rate of 3.5 C/min and
finally held at 250 C for 3 min (analysis time: 63 min). The MS
sourcewas adjusted to 230 C, and a mass range of m/z 35e350was
recorded acquiring all mass spectra in EI mode. Chromatogram
visualization and peak area integration were carried out using
Agilent ChemStation software (Agilent Technologies, Waldbronn,
Germany). Essential oil components were tentatively identified
based on MS database search using NIST/EPA/NIH Mass Spectral
Library (NIST 05) in combination with an in-house retention index
library of MS spectra of volatile organic compounds, and comparison
of spectra with reported MS data in literature (Adams, 2001).