3.4. GC-FID (Gas Chromatography-Flame Ionization Detector) and GC-MS (Gas Chromatography–Mass Spectrometry) Analyses

Hemp volatile compounds were analyzed by GC-FID and GC-MS as described previously [38], with the following modifications: the column temperature was initially set at 40 °C, then increased to 300 °C at a rate of 5 °C/min, which was held for 10 min. The flow rate of the carrier gas (He) was maintained at 1.0 mL/min. The injection volume was 1.0 µL at a split ratio of 30:1. The temperatures of the ionization source, the transfer line, and the injector were 230 °C, 280 °C, and 250 °C, respectively. The MSD was operated in full scan mode. All mass spectra were acquired in electron impact (EI) mode with 70 eV in the m/z range of 40–400. The injector and detector temperature (FID) was set at 220 °C and 280 °C, respectively.

All constituents present in the EO samples were identified by comparing their linear retention indices (LRI) and MS fragmentation patterns with those from the National Institute of Standards and Technology (NIST′08) and Adams mass spectra library. The estimated LRI were determined using a mixture of a homologous series of aliphatic hydrocarbons from C₈ to C₄₀ under the same conditions described above.