Tenax ta

To compare the ST adsorption capacities of the seven phthalates, three types of sorbent packing (QW, GW, and QWTN) were prepared and tested for comparative purposes. Note that for this test, QW and GW were selected for their considerably good sorption capacity for SVOCs like PAHs23 (link). QWTN tubes were also included, as they have been used widely in many previous studies for the collection of SVOCs including phthalates2 9 (link)10 24 (link). To prepare the three types of STs, an empty quartz tube (6.35 mm × 90 mm) was packed individually, containing: (1) 10 mg of QW (Grace, IL, USA), (2) 10 mg of GW (Supelco, PA, USA), and (3) 50 mg of Tenax TA (35–60 mesh, Markes International, UK) and 10 mg of QW (5 mg each at the initial and end of the Tenax TA). After the preparation, all STs were cleaned by supplying pure N₂ gas at 100 mL min⁻¹ at 320 °C for 24 h.

Breath sampling was performed at 3 months after childbirth (follow-up visit 4) following the protocol described by Sola Martínez et al.^{40 (link)}. Briefly, exhaled breath was collected in 1 L Tedlar gas sampling bags. Specifically, mixed breath sample (alveolar and dead space) were collected. Then, the exhaled breath contained in the gas sampling bags was immediately transferred to to thermal desorption tubes (Tenax TA, Markes International) to avoid the diffusion through the bag wall. A room air content sample was also collected directly through Tenax tube for each exhaled breath sample using an Easy-VOC syringe (Markes International) to control for environmental conditions at sampling. Almost all samples were analysed on the same day of collection, being a maximum storage period of less than one week. The Tenax tubes were stored at 4 °C for storage periods longer than one day. Tenax tubes were heated to 335ºC for 25 min for reconditioning after each use. The Tedlar bags were cleaned with 10 nitrogen flushes (99.9% nitrogen purity) before use. Thus, the levels of background artefacts (N,N-dimethylacetamide and phenol) in the gas sampling bags were strongly reduced (Supplementary Fig. S12).

Next to the inhibition experiments, bacterial volatiles emitted in monocultures and pairwise combinations were trapped and analyzed. For trapping of VOCs emitted by bacteria a volume of 100 μl of inoculation suspension was spread on 1/10th TSBA (20 mL) in glass Petri dishes designed for headspace volatile trapping (Garbeva et al., 2014b (link)). The Petri dishes were closed by a lid with an outlet connected to a steel trap containing 150 mg Tenax TA and 150 mg Carbopack B (Markes International, Ltd., Llantrisant, UK; Supplementary Figure S1). All treatments were inoculated in triplicate. The volatiles were collected after 48 and 72 h of incubation and the Tenax steel traps were stored at 4°C until GC-Q-TOF analysis.