Headspace SPME-GC-MS Analysis of VOCs

An aliquot (10 mg) of each sample was placed into a 10 mL headspace vial sealed with a crimped HiSorb septum cap. A metal-core PDMS HiSorb was gently inserted into the vial through the septum. The vial was kept at 60 °C for 3 h for the extraction of VOCs released by each sample tested. The HiSorb probe was removed from the vial and then inserted into an empty TD tube for the analysis. A TD-100 multi-tube auto-sampler (Markes International, Cardiff, UK), equipped with an automated re-collection system, was employed for the thermal desorption of the PDMS probe at 250 °C for 15 min with a nitrogen flow rate of 50 mL/min. During the primary desorption (splitless mode), analytes were cryogenically trapped at 5 °C in an internal focusing trap packed with 70 mg of Tenax GR (Markes International, Cardiff, UK). The cold trap was then desorbed in split mode (split ratio of 11) at 300 °C for 20 min. The GC-MS analyses were performed using the same GC-MS instrumental settings reported elsewhere [45 ]. Briefly, an Agilent 7890 B Gas Chromatograph coupled with an Agilent 7010 GC-MS Triple Quad Mass Detector (Santa Clara, St. Louis, MO, USA) equipped with an Agilent DB-5 ms capillary column (60 m length, I.D. 0.25 mm, and 1 μm film thickness) (Santa Clara, St. Louis, MO, USA) at 1 mL/min of He as the carrier gas was employed. The oven temperature program was 30 °C for 13 min, 4 °C/min to 130 °C (3 min hold time), and 10 °C/min to 220 °C (1 min hold time). The triple quadrupole was operated in both full scan acquiring in the range of m/z 30–300. The temperature of the transfer line, ion source, and quadrupoles were set at 260 °C, 250 °C, and 150 °C, respectively. Helium was used as the quench gas at a flow of 4 mL/min and nitrogen as the collision gas at a flow of 1.5 mL/min. HiSorb probes were conditioned under a N₂ flow rate (70 mL/min) at 280 °C for 2 h.