7890b 7000d gc ms

SCFAs contents were detected using MetWare (http://www.metware.cn/) based on the Agilent 7890B-7000D GC-MS/MS platform. As previously described (22 (link)), 20 mg of fecal samples were accurately weighed and placed in a 2-ml EP tube. A total of 1 ml of phosphoric acid (0.5% v/v) solution and a small steel ball were added to the EP tube. The mixture was grinded for 10 s, three times, then vortexed for 10 min and ultrasonicated for 5 min. A total of 0.1 mL supernatant was added to a 1.5-mL centrifugal tube after the mixture was centrifuged at 12,000 rpm for 10 min at 4°C and 0.5 mL MTBE (containing internal standard) solution was added to the centrifuge tube. The mixture was vortexed for 3 min and ultrasonicated for 5 min. Subsequently, the mixture was centrifuged at 12,000 rpm for 10 min at 4°C, and the supernatant was collected and used for GC-MS/MS analysis.

Concentrations of serum SCFAs (including heptanoic acid) were analyzed using a gas chromatography-mass spectrometer (GC-MS). Serum samples were deproteinized by phosphoric acid and extracted with ether. After being centrifuged at 4000 rpm for 10 min, the supernatant was collected and injected to GC-MS. An Agilent 7890B-7000D GC-MS was fitted with a capillary column HP-INNOWAX 25 m × 0.20 mm × 0.4 μm. The injector temperature was 240 °C, and the carrier gas flow rate was set to 1 mL/min. The ion source and transmission line temperatures were 200 and 250 °C, respectively. The electron bombarding voltage was 70 eV, and single ion monitoring was applied.