Msd chemstation software

Peaks in GC-MS chromatograms were integrated automatically using MSD ChemStation software (version E.02.01.1177, Agilent Technologies, Inc., Santa Clara, CA, USA). Peaks were identified with the Palisade Complete 600K Mass Spectral Library (Palisade Mass Spectrometry, Ithaca, NY, USA) and the NIST Mass Spectral Search Program (The Standard Reference Data Program of the National Institute of Standards and Technology, Gaithersburg, MD, USA). The computer-generated identifications were sorted manually, with a cut-off at 70% identification [35 (link)], into an Excel spreadsheet (Microsoft, Redmond, WA, USA) according to their chemical structure, elution time and origin. When peaks with same retention time were identified as different hydrocarbons in multiple samples, they were treated as n-alkanes at the specific retention time. The relative peak abundances were used in the data input.

With appropriate dose of acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid(Sigma, Germany) and caproic acid(Aladdin, The United States), diethyl ether (Sinopagic Chemical Reagent Company, China) was added to make 10 mixed-standard concentration gradients(0.02 μg/mL, 0.1 μg/mL,0.5 μg/mL, 2 μg/mL,10 μg/mL,25 μg/mL,50 μg/mL,100 μg/mL,250 μg/mL,500 μg/mL). Feces were thawed on ice, and approximately 50 mg of feces were homogenized in 50 μl 15% phosphoric acid. The suspensions were homogenized with a vortex and centrifuged at 15285g for 10min at 4°C. The supernatants were processed for gas chromatography-mass spectrometry on a Thermo TRACE 1310-ISQ gas mass spectrometer (Thermo, Massachusetts, USA). The injection volume was 1 μl, and the split ratio was 10:1. Samples were separated with an Agilent HP-INNOWAX capillary GC column (30 m × 0.25 mm ID × 0.25 µm). The initial temperature was 90°C and was increased to 120°C at 10°C/min, after which the temperature was increased to 150°C at 5°C/min and then to 250°C at 25°C/min, where it remained for 2 min. The carrier gas was helium (1.0 ml/min). The temperatures of the injection port and ion source were 250°C and 230°C respectively under SIM model. Agilent MSD ChemStation software was used for quantitative analysis of chromatographic peak area and retention time (27 (link)).

The chemical components of OS8P were analyzed using a gas chromatograph with mass spectrometry (GC-MS), following the modified method of Chit-aree et al. (19 (link)). Sample preparation involved mixing 0.1 mg of OS8P with 1 ml of anhydrous ether (Merck, Germany). GC-MS analysis was conducted using an Agilent HP 5890 gas chromatography instrument coupled with an Agilent MSD HP 5970 mass selective detector and HP 59970 MS Chemstation with a 59973 NBS mass spectral library (NBS_REVF). A fused silica column of 25 m × 0.20 mm × 0.25 µm film thickness (Varian Inc., Agilent Technologies, USA) was used for separation, and each extracted sample of 1 µl was injected in an injector operation. High-purity helium gas (99.999%) was used as a carrier gas at a 1.0 ml/min flow rate. The ion source and quadrupole mass analyzer were kept at 230 and 150°C, respectively, and the analysis was conducted for 60 min per sample. The MSD Chemstation software (Agilent Technologies) and commercial libraries (NIST02.L, NIST05.L, and Wiley7Nist05.L) were used to identify the chemical compounds of OS8P.