## 3 Materials and Methods  
### Chemical Standards, Material and Real Samples  
Acetonitrile (ACN, CH\({}_{3}\)CN, 99.9%), dichloromethane (DCM, CH\({}_{2}\)Cl\({}_{2}\), 99.9%), \(n\)-hexane (\(n\)-C\({}_{6}\), C\({}_{6}\)H\({}_{14}\), 96%), \(n\)-pentane (C\({}_{5}\)H\({}_{12}\), 95%) and \(n\)-heptane (C\({}_{7}\)H\({}_{16}\), 99%), all of HPLC-grade, were obtained from Carlo Erba (Peypin, France); meanwhile, HPLC-grade methanol (MeOH, CH\({}_{3}\)OH, 99.9%) was acquired from Honeywell (Saint-Germain-en-Laye, France); \(n\)-nonane (C\({}_{9}\)H\({}_{20}\), 99%) and a standard mixture of \(n\)-alkanes C\({}_{10}\)-C\({}_{40}\) (50 mg L\({}^{-1}\) of each in \(n\)-heptane) were purchased from Fluka (St. Gallen, Switzerland). Standards of (+)-x-pinene (\(\alpha\)-pinene; C\({}_{10}\)H\({}_{16}\); 98%; St. Louis, MO, USA), (-)-\(\beta\)-pinene (\(\beta\)-pinene; C\({}_{10}\)H\({}_{16}\); 99%; St. Louis, MO, USA), 1,8-cineole (C\({}_{10}\)H\({}_{18}\)O; 99%; St. Louis, MO, USA), myrcene (C\({}_{10}\)H\({}_{16}\); technical grade; Saint-Quentin, France), \(R\)-(+)-limonene (limonene; C\({}_{10}\)H\({}_{16}\); 97%; Toluca, Mexico) and bromometafluorobenzene (used as an internal standard, IS; C\({}_{6}\)Br\({}_{5}\); 99%; Gillingham, UK) were purchased from Sigma-Aldrich. The stock solutions of the individual analytes and IS were prepared by dissolving them in \(n\)-C\({}_{6}\) to obtain a final concentration of 5000 mg L\({}^{-1}\) and 1000 mg L\({}^{-1}\), respectively. Ultra-pure water was obtained from a Milli-Q water purification system from Merck Millipore (Burlington, MA, EUA). The solutions were stored in glass flasks at \(-20\)\({}^{\circ}\)C and renewed every month. Working standard mixtures (1000 mg L\({}^{-1}\)) and IS (20 mg L\({}^{-1}\)) were prepared daily in \(n\)-C\({}_{6}\) by appropriate dilution from stock solutions. For the HS-SPME assays, a manual holder was used, and the fibers tested were polydimethylsiloxane (PDMS, 100 \(\upmu\)m), polydimethylsiloxane-divinylbenzene (PDMS/DVB, 65 \(\upmu\)m), CarboxenTM-polydimethylsiloxane (CAR/PDMS, 75 \(\upmu\)m) and divinylbenzene-CarboxenTM-polydimethylsiloxane StableFlexTM (DVB/CAR/PDMS, 50/30\(\upmu\)m), which were all obtained from Supelco(Bellefonte, PA, USA). The sorbent phases tested for BAuE devices included four Ps, namely, the reverse phase \(N\)-vinylpyrrolidone polymer StrataTM X (S-X; particle size: 33 \(\upmu\)m; pore size: 85 A, surface area (A\({}_{\rm BET}\)): 800 m\({}^{2}\) g\({}^{-1}\)), the reverse phase styrene-divinylbenzene co-polymer Strata  
Figure 6: Example of total ion chromatograms obtained from assays on the leaves of _E. globulus_ Labill. and _P. pinaster_ Aiton by HS-SPME(PDMS/DVB)/GC-MS (**a,b**) and HS-BAuE(R)/GC-MS (**c,d**), respectively, under optimized experimental conditions. SDB-L (S-DVB; particle size: 100 \(\upmu\)m; pore size: 280 A, surface area (A\({}_{\text{BET}}\)): 500 m\({}^{2}\) g\({}^{-1}\)) and the cyano-based co-polymer Strata(r) CN (S-CN; particle size: 55 \(\upmu\)m; pore size: 70 A, surface area (A\({}_{\text{BET}}\)): 500 m\({}^{2}\) g\({}^{-1}\)), all supplied from Phenomenex (Torrance, CA, USA), as well as the reverse phase \(N\)-vinylpyrrolidone-divinylbenzene co-polymer Oasis(r) HLB (HLB; particle size: 30 \(\upmu\)m; pore size: 80 A, surface area (A\({}_{\text{BET}}\)): 800 m\({}^{2}\) g\({}^{-1}\)) from Waters (Milford, MA, USA).