## 2 Materials and Methods
### Instrumental Analysis  
Samples were analyzed using a Pegasus 4D GC\(\times\)GC-TOFMS (LECO(r) Corporation, St. Joseph, MI, USA) equipped with a secondary oven and a quad-jet, dual-stage, thermal modulator. The \({}^{1}\)D column was an Rtx-5 MS (Restek(r) Corporation, Bellefonte, PA, USA) (30 m \(\times\) 0.25 mm i.d. \(\times\) 0.25 \(\upmu\)m d\({}_{\ell}\)), and the \({}^{2}\)D column was an Rxi-17 Sil MS (Restek(r) Corporation) (1.0 m \(\times\) 0.15 mm i.d. \(\times\) 0.15 \(\upmu\)m d\({}_{\ell}\)). The connection between the two columns was performed used a SiTite \(\upmu\)-union (SGE Analytical Science(r), Wetherill Park, Australia). All samples were run on this column set with settings described in the following paragraphs, but selected samples were further investigated on two other column sets: Rxi-624 Sil MS \({}^{1}\)D column (Restek(r) Corporation) (30 m \(\times\) 0.25 mm i.d. \(\times\) 1.40 \(\upmu\)d\({}_{\ell}\)) \(\times\) Stabilwax \({}^{2}\)D column (Restek(r) Corporation) (2 m \(\times\) 0.25 mm i.d. \(\times\) 0.50 \(\upmu\)d\({}_{\ell}\)); Stabilwax \({}^{1}\)D column (25 m \(\times\) 0.25 mm i.d. \(\times\) 0.50 \(\upmu\)d\({}_{\ell}\)) \(\times\) Rtx-200 Sil MS \({}^{2}\)D column (Restek(r) Corporation) (1 m \(\times\) 0.25 mm i.d \(\times\) 0.25 d\({}_{\ell}\)).  
The sample vials were extracted using automated HS-SPME with a multipurpose sampler (MPS) (Gerstel(r)). A 50/30 \(\upmu\)m divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) Stableflex 24 Ga fiber was chosen (Supelco(r), Bellefonte, PA, USA) based on previous literature [5] and experience characterizing similar types of expected volatiles. Each vial was first incubated at 50 \({}^{\circ}\)C for 10 min. The fiber was exposed for 15 min to the headspace of each sample with a penetration depth of 21.00 mm. The fiber was desorbed with a penetration depth of 54.00 mm for 180 s in a CIS4 Cooled Injection System (Gerstel(r)). The injector temperature was programmed at \(-\)10 \({}^{\circ}\)C for 0.15 min, was increased to 350 \({}^{\circ}\)C at 12.00 \({}^{\circ}\)C\(\cdot\) s\({}^{-1}\), and then held at 350 \({}^{\circ}\)C for 5.00 min. The injection was performed in splitless mode with a 3 mL\(\cdot\)min\({}^{-1}\) septum purge flow and a purge time of 120 s. The inlet purge flow was 20 mL\(\cdot\)min\({}^{-1}\).  
High purity helium (Air Liquide(r), Liege, Belgium) carrier gas flow was held at a constant rate of 1.00 mL\(\cdot\)min\({}^{-1}\) throughout the run. The \({}^{1}\)D oven was held initially at 50 \({}^{\circ}\)C for 3 min, followed by an increase to 220 \({}^{\circ}\)C at a rate of 5\({}^{\circ}\)C\(\cdot\)min\({}^{-1}\) (total 37 min). The \({}^{2}\)D oven offset was \(+\)15 \({}^{\circ}\)C above the \({}^{1}\)D oven temperature and the modulator offset was \(+\)20 \({}^{\circ}\)C from the \({}^{2}\)D oven. A 3 s modulation period (\(P_{\mathrm{M}}\)) was used with a 0.40 s hot pulse time. An acquisition delay of 300 s was used. The MS transfer line was held at 220 \({}^{\circ}\)C. The mass acquisition range was 29-450 amu and operated with a rate of 100 Hz. The ion source temperature was 230 \({}^{\circ}\)C and the electron ionization energy was 70 eV. The detector voltage was 1500 V.