Agilent 7000d mass spectrometer

An Agilent 7890B GC system coupled with an Agilent 7000D mass spectrometer (Agilent Technologies, Santa Clara, CA, USA) was used to identify the volatile compounds in the various samples using an Agilent DB-5MS capillary column (30 m × 0.25 mm × 0.25 μm) and helium (purity > 99.999%) as the carrier gas at a flow rate of 1 mL/min. The front injection temperature and inlet mode were set to 250 °C and splitless. The GC oven temperature was set to 40 °C for 1 min, and then increased to 280 °C at 5 °C/min. EI energy of 70 eV was used during MS, the ion source and quad temperatures were at 230 °C and 150 °C, respectively. Full-scan acquisition mode (from 30 to 350 aum) was used with a solvent delay time of 3.0 min.

At the end of the 7-day-experimental period (1 × 10⁸ CFU C. butyricum/mL), mice were euthanized, and uterus and blood samples were collected. Blood was kept on ice for 30 min and centrifuged at 3,500 rpm for 10 min at 4°C, and serum was obtained for analysis. The samples obtained for measurement of butyric acid (a short-chain fatty acid) were immediately frozen at −20°C and stored at −80°C until quantification. Butyric acid measurement was determined following a modified protocol, as previously described. First, a standard curve sample was prepared. Next, the SCFA-containing ether layers were obtained and pooled for GC-MS analysis using an Agilent 7890 gas chromatography system coupled with an Agilent 7000D mass spectrometer. The mass spectrometry data were acquired in MRM mode with a solvent delay of 3 min.