Quantitative GC-MS/MS Analysis of Volatiles

VPs were quantitated exactly as previously described using GC–MS/MS [7 (link),10 (link),20 (link)]. In brief, a Trace 130 gas chromatograph equipped with a TSQ9000 triple quadrupole mass spectrometer (GC–MS/MS; both from Thermo Fisher Scientific; Waltham, MA, USA) was used to acquire all date in selected reaction monitoring mode. The GC column used was a Zebron ZB-5MSplus (30 m × 0.25 mm × 0.25 μm; Phenomenex; Torrence, CA, USA) and helium was used as the carrier gas (1.5 mL/min). A split ratio of 1:4 was used and 1 μL was selected as the injection volume. The GC oven and MS system parameters including all transitions were exactly as previously used [7 (link),10 (link),21 (link)]; see Figure S1Supplemental for representative extracted ion chromatograms for all analytes.