GC/MS Analysis of Essential Oil Composition

The chemical composition of the essential oils was evaluated by gas chromatography/mass spectrometry (GC/MS) according to the methodologies by [53 (link),54 (link)], using a Shimadzu QP-2010 plus system under the following conditions: silica capillary column Rtx-5MS (30 m × 0.25 mm, 0.25 μm film thickness); program temperature of 60–240 °C at 3 °C/min; injector temperature of 250 °C; helium as carrier gas (linear velocity of 32 cm/s, measured at 100 °C); splitless injection (1 μL of a 2:1000 hexane solution). Ionization was obtained by electronic impact technique at 70 eV, and the temperature of the ion source and other parts was set at 200 °C. The quantification of volatile compounds was determined by gas chromatography with a flame ionization detector (FID; Shimadzu, QP 2010 system-Kyoto, Japan) under the same conditions as gas chromatography coupled to mass spectrometry (GC-MS), except that hydrogen was used as the carrier gas. The retention index was calculated for all volatile constituents using a homologous series of n-alkanes (C₈–C₂₀), and were identified by comparing the mass spectra obtained experimentally and their retention indices to those found in literature [46 ,47 ].