GC-MS Analysis of Derivatized Samples

Derivatized samples were analyzed by GC-MS (Agilent 5977 Series GC/MSD, Agilent Technologies, Santa Clara, CA, USA) [15 (link)]. Trimethylsilyl derivatives (1 μL) were injected into an injector at 230 °C in splitless mode. The oven temperature ramp applied was 80 °C (initial temperature), held for 2 min, heated at 15 °C.min⁻¹ to 330 °C, and held for 6 min. The electron impact ionization mass spectrometer was set at ionization voltage 70 eV; ion source temperature 250 °C; injection port temperature 250 °C; and mass scan range 70–600 m/z at 20 scans.s⁻¹. The column used was an HP5ms column (30 m × 0.25 m × 0.25 μm). The flow rate of helium gas was 2 mL.min⁻¹. Acquisition, deconvolution, and analyses of experimental data were processed by MassHunter Quantitative Analysis software (Agilent, CA, EUA). The NIST mass spectral library (NIST 2011, Gaithersburg, MD, USA) was used for retention index (RI) comparison and data validation. Some of the identified metabolites were also confirmed by mass spectral comparison with the authentic external standards previously described.