3.6. Gas Chromatography and Mass Spectrometry Analysis of VOCs

The GC-FID analyses of volatiles were carried out with an Agilent Technologies (Palo Alto, CA, USA) gas chromatograph model 7890A equipped with a flame ionization detector (FID) and a HP-5MS capillary column (5% phenyl-methylpolysiloxane, Agilent J and W). The GC-MS analyses were performed on an Agilent Technologies (Palo Alto, CA, USA) gas chromatograph model 7890A equipped with a mass selective detector (MSD) model 5977E (Agilent Technologies) and HP-5MS capillary column, under the same conditions as for the GC-FID analysis. The GC conditions and the detail procedure are described in our previously published paper [53]. The identification of the compounds was based on the comparison of their retention indices (RI), determined relative to the retention times of C₉–C₂₅ homologous series of n-alkanes with those reported in the literature and on the comparison of their mass spectra with available authentic compounds or with the mass spectra listed in Wiley 9 (Wiley, New York, NY, USA) and NIST 14 (D-Gaithersburg) mass spectral libraries. The percentage composition of the samples was computed from the GC peak areas using the normalization method (without correction factors). The average component percentages in Table 1 were calculated from duplicate GC-FID and GC-MS analyses. One-way analysis of variance (ANOVA) and multiple comparisons (Duncan’s post-hoc test) were used to evaluate the significant difference of the data at p < 0.05 (Table 1.).