Agilent 7890b 5977b gc ms system

Gas chromatography–mass spectrometry (GC-MS) was used for the metabolic analysis of cecum contents. The processed samples were prepared as previously mentioned [23 (link)] and then analyzed using an Agilent 7890B-5977B GC-MS system (Agilent, Santa Clara, CA, USA). Metabolites were identified by NIST and further analyzed.
For the quantitative analysis of SCFAs in cecum contents, the samples were mixed with water, vortexed, centrifuged, and mixed with ethyl acetate. After centrifugation, the supernatant was incubated and then transferred to sample tubes for further analysis [20 (link)].

Petunia flower volatiles were collected by a closed-loop stripping method and analyzed by GC-MS as described previously^{66 (link)} with minor modifications. Briefly, volatiles were collected from 20:00 to 21:00 h from a minimum of three 2-day-old flowers per biological replicate. Absorbed volatiles were eluted from collection traps containing 20 mg of Porapak Q (80-100 mesh) (Waters, Milford, MA) with 200 μl DCM supplemented with 1 μg of naphthalene as internal standard. For the analysis of internal pools, 100 mg of ground tissue was extracted twice at 4 °C with 500 μL DCM containing 1 μg naphthalene as internal standard. The extracts were pooled together and concentrated to about 200 μL under a mild stream of nitrogen gas. Samples were analyzed on an Agilent 7890B-5977B GC-MS system using an analytical method translated from established method with Agilent 6890N-5975B GC-MS system as previously described^{66 (link)}. Quantitation of different volatile compounds was performed based on standard curves generated with authentic standards.