3.5. The GC-MS Analysis of Diethyl Ether Extracts

The GC–MS analysis of volatiles present in extracts was performed with a Shimadzu GC-2010 Plus GC instrument coupled with a Shimadzu QP2010 Ultra mass spectrometer (Kyoto, Japan). The analytes were separated on a ZB-5 MS capilary column (30 m, 0.25 mm i.d.) with a film thickness of 0.25 m (Phenomenex, Torrrance, CA, USA). The oven temperature program was as follows: 50 °C initially for 3 min, increased to 250 °C at 5 °C/min, and held for 5 min; and finally the temperature was increased to 320 °C at the rate of 10 °C/min and held for 5 min. The total time of analysis was 60 min. Helium was used as a carrier gas of 1.0 mL/min flow rate. A split injection was performed with a split ratio of 1:20. The injector port, interface and ion source temperatures were kept at 280, 250 and 220 °C, respectively. The spectrometer was operated in the electron impact mode, the scan range was 40–600 amu, the ionization energy was 70 eV and the scan rate was 0.20 s per scan. The retention indices were determined by analyzing a solution containing the homologous series of n-alkanes (C8–C34) under the same operating conditions. Compounds were identified using computer-assisted spectral libraries (MassFinder 2.1; NIST 2011).