## 3 Materials and Methods
### Terpenes GC-MS Analysis  
One hundred mg of each oil sample were weighed and put into 20 mL glass vials along with 100 \(\upmu\)L of the invernal standard (IS, 4-nonylphenol, 2000 \(\upmu\)g/mL in 2-propanol). Each vial was fitted with a cap equipped with a silicon/PTFE septum (Supelco). A temperature of 37 \({}^{\circ}\)C was selected as both as the extraction and equilibration temperature according to previous published research, in order to prevent possible matrix alterations ensuring the most efficient adsorption of volatile compounds onto the SPME fibre [15; 16]. To keep the temperature constant during analysis, the vials were maintained in a cooling block (CTC Analytics, Zwingen, Switzerland). At the end of the sample equilibration time (30 min), a conditioned (60 min at 280 \({}^{\circ}\)C) SPME fiber was exposed to the headspace of the sample for 120 min using a CombiPAL system injector autosampler (CTC Analytics). All analytical parameters were already validated in our previous research [12]. Analyses were performed with a Trace GC Ultra coupled to a Trace DSQII quadrupole mass spectrometer (MS) (Thermo-Fisher Scientific, Waltham, MA, USA) equipped with an Rtx-Wax column \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Samples**} & \multicolumn{1}{c}{**CBD Declared**} & \multirow{2}{*}{**Matrix**} & \multirow{2}{*}{**Origin**} & **Extraction Method** \\  & **Content** (\%, \(\upmu\)/\(\upmu\)s) & & & **(When Indicated)** \\ \hline Oil\_1 & / & Olive oil & Italy & Calvi et al., 2018 \\ Oil\_2 & 4 & Hemp seed oil & Switzerland & ND\({}^{*}\) \\ Oil\_3 & 1 & Olive oil & Switzerland & ND \\ Oil\_4 & 5 & Caprylic/Capric Triglyceride (MCT) & Italy & ND \\ Oil\_5 & 4 & Olive oil & Switzerland & CO\({}_{2}\) supercritical \\ Oil\_6 & 3 & Hemp oil & The Netherlands & CO\({}_{2}\) supercritical \\ Oil\_7 & 4 & Olive oil & Spain & ND \\ Oil\_8 & 3 & Hemp seed oil & The Netherlands & ND \\ Oil\_9 & 3 & Hemp seed oil & The Netherlands & ND \\ Oil\_10 & 4 & Olive oil & The Netherlands & ND \\ Oil\_11 & / & Hemp seed oil & Switzerland & ND \\ Oil\_12 & 2 & Hemp seed oil & Switzerland & CO\({}_{2}\) supercritical \\ Oil\_13 & 4 & Olive oil & France & ND \\ Oil\_14 & 5 & Hemp seed oil & Slovenia & CO\({}_{2}\) supercritical \\ Oil\_15 & 3 & Hemp seed oil & UK & ND \\ \hline \hline \end{tabular} \({}^{*}\)ND—not declared.  
\end{table} 
Table 3: Declared CBD content, oil matrix used and origin of the analysed CBD oil samples. (30 m \(\times\) 0.25 mm i.d. \(\times\) 0.25 \(\upmu\)m film thickness) (Restek, Bellefonte, PA, USA). The oven temperature program was: from 35 \({}^{\circ}\)C, held for 8 min, to 60 \({}^{\circ}\)C at 4 \({}^{\circ}\)C/min, then from 60 to 160 \({}^{\circ}\)C at 6 \({}^{\circ}\)C/min and finally from 160 to 200 at 20 \({}^{\circ}\)C/min. Helium was the carrier gas, at a flow rate of 1 mL/min. Carry over and peaks originating from the fibres were regularly assessed by running blank samples. After each analysis fibres were immediately thermally desorbed in the GC injector for 5 min at 250 \({}^{\circ}\)C to prevent contamination. The MS was operated in electron impact (EI) ionisation mode at 70 eV. An alkanes mixture (C8-C22, Sigma R 8769) was run under the same chromatographic conditions as the samples to calculate the Kovats Retention Indices (RI) of the detected compounds. The mass spectra were obtained by using a mass selective detector, a multiplier voltage of 1456 V, and by collecting the data at rate of 1 scan/s over the _m/z_ range of 35-350. Compounds were identified by comparing the retention times of the chromatographic peaks with those of authentic compounds analyzed under the same conditions when available, by comparing the Kovats retention indices with the literature data and through the National Institute of Standards and Technology (NIST) MS spectral database. The quantitative evaluation was performed using the internal standard procedure and the results were finally expressed as \(\upmu\)g/g or mg/g IS equivalents of each volatile compounds.