Gas Chromatography-Mass Spectrometry Analysis of Essential Oils

Essential oils were chemically analyzed [25 (link)] within two months of their production date. Ten microliter of each essential oil sample was added into a clear screw-top GC-vial (6.0 mm diameter, silicone septa, 2 mL volume), and then 1.5 mL of dichloromethane was added to each vial. A blank containing only dichloromethane was included to confirm its purity. Essential oils were analyzed using a gas chromatography apparatus equipped with a quadruple mass spectrometer (GC-MS) (Shimadzu, GC-MS-QP/5050A). A nonpolar capillary column (DB-5MS, thickness; 0.25 μm, length; 30 m, internal diameter; 0.25 mm) was used to separate the components of the essential oils using a splitless mode. The temperature was kept at 51 °C for 1 min and then raised to 211 °C at a rate of 3 °C min⁻¹. The injector temperature was 275 °C, and the interface temperature was 300 °C. Helium was used as the carrier gas. Chemical compounds were identified by matching their fragmentation patterns in the resultant mass spectra with those stored in the computer’s mass spectral database.