The content of fecal SCFAs was determined using gas chromatography–mass spectrometry (GC–MS-QP2010 Ultra, Shimadzu, Japan) and quantified relative to acetic acid (Sigma-Aldrich, United States, BCCD6436), propionic acid (Sigma-Aldrich, United States, BCCF1438), isobutyric acid (Sigma-Aldrich, United States, CRACA252), butyric acid (Dr. Ehrenstorfer GmbH, Germany, 976513), isovaleric acid (Sigma-Aldrich, United States, BCCD7896), and isovaleric acid (Sigma-Aldrich, United States, BCCF0934).
After processing the samples were then subjected to GC–MS analysis using a Shimadzu capillary column WM-5MS (30 m × 0.25 mm × 0.25 μm), an injection volume of 0.5 μL at a split injection ratio of 30:1, and injection port, ion source, and transfer line temperatures of 250°C, 200°C, and 220°C, respectively. The temperature program was as follows: 27°C for 3 min, increased to 110°C at a rate of 4°C/ min, further increased to 250°C at a rate of 4°C/min, and maintained at 250°C for 1 min. Helium was used as a carrier gas at a flow rate of 1.0 mL/min. Mass spectrometry (MS) conditions were as follows: electron bombardment ion source, electron energy of 70 eV, and full scan (30–350 m/z).
After processing the samples were then subjected to GC–MS analysis using a Shimadzu capillary column WM-5MS (30 m × 0.25 mm × 0.25 μm), an injection volume of 0.5 μL at a split injection ratio of 30:1, and injection port, ion source, and transfer line temperatures of 250°C, 200°C, and 220°C, respectively. The temperature program was as follows: 27°C for 3 min, increased to 110°C at a rate of 4°C/ min, further increased to 250°C at a rate of 4°C/min, and maintained at 250°C for 1 min. Helium was used as a carrier gas at a flow rate of 1.0 mL/min. Mass spectrometry (MS) conditions were as follows: electron bombardment ion source, electron energy of 70 eV, and full scan (30–350 m/z).
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