Ms 5973n

The measurement of different components of PAHs in the samples were performed by a gas chromatography–mass spectrometry (GC 6890, AGILENT, MS 5973N, Mode EI, detector:MS).
Generally, the concentrations 16 different aromatic compounds: Acenaphthylene, Naphthalene, Acenaphthene, Phenanthrene, Anthracene, Fluoranthene, Fluorene, Pyrene, Chrysene, Benzo(b)fluoranthene, Benzo(k)fluoranthene, Benzo(a)anthracene, Benzo[a]pyrene, Indeno(1,2,3,cd)pyrene, Benzo(g.h.i)perylene, Dibenz[a,h]anthracene were analyzed according to EPA method 3500C^{21 (link)} and National standard of Iran (19,238)²² .

SPME fiber containing the adsorbed analytes was introduced into the split–splitless injector of the gas chromatograph (GC 6890 N; Agilent, Santa Clara, CA, United States) coupled to the mass spectrometer (MS 5973 N; Agilent, Santa Clara, California, United States). The thermal desorption of the analytes occurred at 250 ° C for 10 min. The oven temperature was maintained at 50°C for 2 min and increased from 50°C to 150°C at 10°C/min and from 150°C to 280°C at 15°C/min. The injection and ion source temperatures were 250°C and 230°C, respectively, and helium (99.999%) was used as a carrier gas with a flow rate of 1 ml min⁻¹. The gas chromatograph was equipped with a capillary column (30 m × 0.250 mm) coated with a 0.25 μm 5% diphenyl/95% dimethylpolysiloxane film (Supelco^®, Bellefonte, PA, United States). The mass spectrometer was set at 70 eV. Identification of VOCs identification was performed using the National Institute of Standards and Technology (NIST) Atomic Spectra Database version 1.6 (U.S. Department of Commerce, Gaithersburg, Maryland, United States).

SCFA and BCFA levels were determined in the fecal supernatants by means of gas chromatography, as described by Moris et al.^{77 (link)} Briefly, 250 μl of cell free-supernatants were mixed with 100 μl methanol, 50 μl internal standard solution (2-ethylbutyric 1.05 mg/ml), and 50 μl of 20% v/v formic acid. The mix was then centrifuged, and the supernatant was injected into a system composed of a 6890NGC injection module (Agilent Technologies Inc., USA) connected to a flame injection detector (FID) and a mass spectrometry detector (MS, 5973 N) (Agilent) for quantification of both SCFA and BCFA.

An Agilent 6890N gas chromatograph coupled with a mass spectrometer (MS 5973N, Agilent Technologies, Santa Clara, CA) was used in this study. First, one μL of SAFE extracts or SPME fiber extracts was injected in splitless mode onto both DB-wax column (60 m length, 0.25 mm i.d., 0.25 μm film thickness, J&W Scientific, Folsom, CA, USA) and DB-5ms column (60 length, 0.25 mm i.d., 0.25 μm film thickness, J&W Scientific, Folsom, CA, USA), respectively. Helium was used as the carrier gas with flow rate of 1 mL/min. The temperature program parameters of mass spectrometer were the same as our newly published paper [26 (link)].