GC and GC–MS analysis methods were used to determine the composition of the essential oils. GC analysis was done on an Agilent Technologies 7890 gas chromatograph equipped with Flame Ionization Detector (FID) and a HP-5MS 5% capillary column (30.00 m 0.25 mm, 0.25 lm film thicknesses). Oven temperature was kept at 60 C for 4 min initially, and then raised at the rate of 4 C/min to 260 C. Injector and detector temperatures were set at 290 C and 300 C, respectively. Helium was used as carrier gas at a flow rate of 2 ml/min, and 0.1 ll samples were injected manually in the split mode. Peak areas were used for quantifying the constituent percentage in total oil. The gas chromatograph was coupled to an Agilent 5975 C (Agilent Technologies, Palo Alto, CA, USA) mass selective detector. Operating parameters for the EI-MS were: ionization voltage, 70 eV; ion source temperature, 200 C. Retention indices were calculated for all components using a homologous series of n-alkanes (C
5
–C
) injected in conditions equal to the oil samples. Identification of oil components was accomplished based on comparison of retention times with those of authentic standards, and by comparison of their mass spectral fragmentation patterns (WILLEY/ChemStation data system) (Adams, 2007). Area percent was obtained electronically from the GC–FID responses without the use of an internal standard or correction factors.
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