GC-MS (gas chromatography-mass spectrometry) analysis of the essential oils extracted from German and Roman chamomile flowers

The essential oils of German chamomile and Roman chamomile flowers were extracted using steam distillation. Dried samples (50 g) were crushed and were then refluxed for 8 h in a round bottom flask containing 1000 ml of pure water. We analyzed samples with three biological replicates. GC conditions: The analytes were separated using an HP-5MS column (30 m × 0.25 mm I.D. × 0.25 μm film thickness; Agilent Technologies, USA); the carrier gas was high-purity helium (99.999%, Airgas Inc.); the flow rate was 1 mL/min; the injector temperature was 280 °C; The injection mode was split, and the split ratio was 10:1. The oven temperature was maintained at 70 °C for 3 min, then programmed to rise from 70 °C to 180 °C at the rate of 5.5 °C/min, and was then held at 180 °C for 4 min. The temperature was programmed to rise to 280 °C at the rate of 4 °C/min, and was then held at 280 °C for 2 min. MS conditions: the transfer line temperature was 280 °C; ionization mode, electron impact (EI) at 70 eV; the quadrupole temperature was 150 °C; scan range, m/z 29–420; scan rate, 3.75 scans/s; with an ion source temperature of 230 °C. Compounds were identified by comparing the mass spectra and retention indices with spectra in the NIST database [51]. We used ethyl caprate as the internal standard to calculate relative peak ratios (peak area of compounds/ peak area of ethyl caprate) in German chamomile and Roman chamomile.