Supel q plot

Prior to the methanol analysis at each time point, the septa-sealed vial (20 mL) was placed in an oven at 70 ^oC for 15 min to totally evaporate the methanol produced in the reaction solution into the gas phase of headspace. Then, 1 mL of headspace gas was injected into a Supel-Q PLOT capillary gas chromatography (GC) column (Supelco, Pennsylvania, USA) installed in a GC equipment (7890B GC, Agilent, California, USA). The amount of methanol was quantified using a pre-determined correlation between the mass of commercial methanol standard (Sigma-Aldrich, St. Louis, USA) and calculated area of methanol peak using a GC software (OpenLAB CDS ChemStation C.01.07, Agilent).

IT-SPME was essentially performed as described in our previous works [31 (link),32 (link)]. A GC capillary column (60 cm × 0.32 mm i.d.) as an extraction device was connected between the injection needle and injection loop of the autosampler. The capillary column was threaded through a 1/16 inch polyetheretherketone (PEEK) tube with a length of 2.5 cm long and an inner diameter of 330 μm and connected using standard 1/16 inch stainless steel nuts, ferrules, and connectors. CP-Sil 5CB (100% polydimethylsiloxane, film thickness 5 μm), CP-Sil 19CB (14% cyanopropyl phenyl methylsilicone, film thickness 1.2 μm) (Varian Inc., Lake Forest, CA, USA), Supelco-Wax (polyethylene glycol, film thickness 1.0 μm), Supel-Q PLOT (divinylbenzene polymer, film thickness 17 μm), and Carboxen 1006 PLOT (carbon molecular sieve, film thickness 15 μm) (Supelco, Bellefonte, PA, USA) were used to compare extraction efficiencies. Extraction, desorption, and injection parameters were programmed by the autosampler software (Table S1) [31 (link),32 (link)].

In tube, SPME was essentially performed as described in our previous works [24 (link),29 (link)]. A GC capillary column (60 cm × 0.32 mm i.d.) as an extraction device was connected between the injection needle and injection loop of the autosampler. The capillary column was threaded through a 1/16 inch polyetheretherketone (PEEK) tube with a 2.5 cm long, 330 μm inner diameter and connected using standard 1/16 inch stainless steel nuts, ferrules and connectors. Supel-Q PLOT (Supelco, Bellefonte, PA, USA), Carboxen 1010 PLOT (Supelco), CP-Sil 5CB (Varian Inc., Lake Forest, CA, USA), CP-Sil 19CB (Varian), CP-Wax 52CB (Varian), and Quadrex 007-5 (Quadrex Corporation, Woodbridge, CT) were used to compare extraction efficiencies. The control of extraction, desorption, and injection was programmed by the autosampler software (Table S2) [24 (link),29 (link)].