Db 5ms quartz capillary column

A DB-5MS quartz capillary column (30 m × 0.25 mm × 0.25 μm, Agilent J&W Scientific, Folsom, USA) was used. The injector temperature was set to 280 °C, the injection volume was 1 μL, and the split ratio was 1:1. The flow rate of helium (carrier gas, 99.999%) was set to 1.0 mL/min. The column temperature was initially 70 °C, and this temperature was held for 4 min, gradually increased at a rate of 20 °C/min to 110 °C and then at a rate of 8 °C/min to 270 °C and then held for 5 min. The temperature of the electron ionization source was 200 °C. The solvent delay duration was 6.5 min, and the MS scanning range was 35–550 m/z. During the analysis, the sample injection sequence was randomly arranged, and one quality control (QC) sample was added every nine samples.

Thermolysis of PEOM was carried out as the description by our group with some modifications (29 , 30 ). 500 mg of PEOM was put into an offline pyrolysis tank (OLT) self-made by our research group. And then, the OLT was sealed and placed in an automatic temperature-controlled electric furnace (Furnace 1,000°C, Tianjin, China) (31 ). The furnace temperature reached 100°C, and nitrogen as the carrier gas passed continuously through OLT for 10 min, meanwhile, decomposition products blown by carrier gas were absorbed by the mixture (hexane: methylene chloride: ethyl acetate = 1:1:1). Thermal decomposition products were detected by using the method of GC/MS (Agilent, Palo Alto, CA, USA). DB-5MS quartz capillary column (30 m × 0.25 mm × 0.25 μm, Agilent, USA) was used for the GC/MS analysis. Helium (99.999%) was used as carrier gas; the injector was at 250°C and the gas flow rate was set to 1.0 ml/min with splitting mode. Instrument conditions were as follows: initial temperature was set at 50°C for 3 min, then followed with a rate of 7°C/min up to 280°C, and kept for 10 min. The ion source of MS was set from 45 to 500 (m/z) with electron ionization of 70 eV. Temperature of ion source and quadrupole were 230°C and 150°C, respectively. Mass spectrometric data of constituents was retrieved from MS databases of NIST14, peak area percentage was employed to proceed with quantitative analysis.

The GC-MS was performed as previously described (Cao et al., 2020 (link)), using Gas Chromatography-Mass Spectrometer (7,890B–5977B, Agilent Technologies, CA, United States) equipped with a DB-5MS quartz capillary column (0.25 mm × 30 mm, 0.25 μm). Analysis was performed using 1 µL injection volume with helium as the carrier gas (99.999%). The flow rate was 1.0 ml/min and a split ratio of 10:1. The column temperature was maintained at 60°C for 1 min, then increased at a rate of 10°C/min up to 250°C and maintained at 250°C for 10 min. The injection temperature was 250°C, while that of the electron bombardment ion source was 230°C, with a solvent delay of 5.9 min and a scanning range of the mass spectrum at m/z 50.0–600.0.