Essential Oil Chemical Profiling by GC-MS

The EO was diluted with n-hexane (GC grade, 5 μL:1 mL) and 5 μL were injected into the GC (GC, Model CP-3800, Varian, Walnut Creek, CA, USA) and linked with a mass spectrometer (MS, Model Saturn 2200, Varian, Walnut Creek, CA, USA) equipped with a VF-5ms-fused silica capillary column (5% phenyl-dimethylpolysiloxane, with dimensions of 30 m × 0.25, film thickness was 0.25 μm, Varian). An electron impact (EI) ionization detector was used, with an ionization energy of 70 eV. Carrier gas (helium) was adjusted to have a steady flow rate (1 mL/min). The temperature of the oven was programed as follows: 1, 50, and 5 min at 50, 230, and 290 °C, respectively. The split ratio of injection samples was 1/500, with total time equal to 60 minutes. Identification of the constituents was conducted by comparison of Kovat’s retention indices (RI) relative to a set of co-injected standard hydrocarbons (C10–C28, Sigma-Aldrich, Darmstadt, Germany) [52 (link)]. Components were identified by comparing their MS data and their corresponding retention indices with the Wiley Registry of Mass Spectral Data 10^th edition (April 2013), the NIST 11 Mass Spectral Library (NIST11/2011/EPA/NIH), and literature data [53 ]. All of the identified constituents and their relative abundance percentages are listed in Table 1.