Components analysis of volatile oils by GC–MS analysis

The analysis of the volatile oil was performed using Agilent 7890A-5975C GC–MS (Agilent technologies company in the United States), equipped with a HP-5MS capillary column (30 m × 0.25 mm, film thickness 0.25 μm) for the separation. The mass-selective detector was operated in electron impact ionization (EI) mode with a mass scan range from m/z 40–550 at 70 eV. Helium (He) was used as the carrier gas at a flow rate of 1 mL/min. Injector and MS transfer line temperatures were set at 250 and 170 °C, respectively. A sample of 1.0 μL of volatile oil was injected manually using a 5:1 split ratio. The temperature program was as follows: initial temperature of 75 °C held for 2 min, followed by the ramping up of the temperature at a rate of 5 °C/min up to 130 °C, which was held for 7 min, 2.5 °C/min up to 170 °C for 10 min, finally 5 °C/min up to 250 °C for 10 min. The temperature of the MSD transfer line was 250 °C. The temperature of the ion source was 230 °C, and that of the MS quadrupole was 280 °C.

The components were identified by comparing their GC retention indices, NIST mass spectral search program (Version 2.0, National Institute of Standards and Technology), and mass spectra with published data. The compounds were tentatively identified on the basis of their retention times and by interpretation of MS fragmentation patterns with those of standard libraries NIST11. Amounts of the detected volatiles were based on comparison of their peak areas. One-way analysis of variance (ANOVA) and Duncan’s multiple range tests were carried out to compare significant differences (at the 5% significance level, p < 0.05) between treatments using the statistical package SPSS 20.0 for Windows.