2.3. Gas chromatography–mass spectrometry (GC–MS)
GC analysis was performed on a Shimadzu GCMS-QP 2010Ultra gas chromatograph fitted with flame ionization detector (FID)and RTX–5 column (30 m × 0.25 mm, film thickness 0.25 m) withhelium as carrier gas at 1.33 ml/min. The injection port was main-tained at 210◦C, the detector temperature was 230◦C. The splitratio was 1:10 and ionization voltage maintained at 70 eV. OneL sample was injected. The oven was programmed as follows:at 40◦C for 2 min and then increased to 210◦C at 5◦C/min at whichthe column was maintained for 5 min. Identification of volatileswas based on retention indices calculated by using n-hydrocarbons(C9C22) and mass spectra by computerised matching of essentialoil compounds with NIST 2008 and Wiley libraries. 1,8-Cineole and-terpinyl acetate were confirmed and quantified by co-injectionof external standard compounds. In order to evaluate the amount of1,8-cineole and -terpinyl acetate in samples, standards at differ-ent concentration levels were selected according to their relativeamounts in the sample, ranging from 400 to 800 mg/dL. Linear cal-ibration curves were obtained with correlation coefficients R2of0.999 and 1.000 for -terpinyl acetate and 1,8-cineole, respectively.