GC-MS Analysis of Essential Oils

EOs were analyzed with the same method and instrument as in our previous work [18 (link)]. We used a Hewlett Packard gas chromatograph (HP 6890 series GC) with a Hewlett Packard 5973 mass detector. The instrument was equipped with a high-temperature ZB-5HT (5% diphenyl- and 95% dimethyl-polysiloxane) 30 m long capillary column with an inner diameter of 0.32 mm and a film thickness of 0.25 μm (Phenomenex Inc., Torrance, CA, USA). EOs (20 µL) were diluted with dichloromethane (Sigma-Aldrich ACS Grade, Merck, Darmstadt, Germany) and directly analyzed. We injected 1 μL of a sample using the a split injection technique with a split ratio of 20:1 and an injector temperature of 250 °C. Helium was used as the carrier gas, and its flow rate was 2 mL/min. The temperature oven program was 40–180 °C with a heating rate of 5 °C/min and 180–280 °C with a heating rate of 10 °C/min. The solvent delay was three minutes. Peaks were identified by comparing the mass spectra data with the NIST 11 Library and by comparing their retention indices with literature values. In some cases, comparisons with standards were necessary. Retention index mixture, the terpineol mixture of isomers, and sabinene hydrate analytical standards were obtained from Merck. Amounts of the detected components represent % abundance (area percent, solvent peak excluded).