The analyses were performed with the Gas Chromatograph Perkin-Elmer AutoSystem XL equipped with an automatic sampler for liquid sample injections and with the TotalChrom™ chromatography software (Perkin Elmer Italia S.p.A., Milano (MI), Italy).

To obtain the separation of the enantiomeric monoterpenes, an Elite-Betacydex Betacyclodextrin capillary column (Perkin Elmer Italia S.p.A., Milano (MI), Italy), 30 m long and 0.25 mm in diameter, was used. GC analysis was carried out using hydrogen as a carrier gas at 2.0 mL·min–1 by a flame ionization detector at 250 °C and at injector temperature of 230 °C. The oven temperature programming started at 40 °C for 3 min and increased to 200 °C, at 1 °C·min–1, and the final temperature of 200 °C was maintained for 10 min. Volatile terpenes were identified by comparison of their retention times with those of standards under the same conditions. High-purity components were obtained from Sigma-Aldrich (Steinheim, Germany). Absolute amounts of terpenoids (total concentrations) were determined by comparison with the tridecane internal standard, and expressed as mg g–1 fresh weight (FW). Relative amount (proportion or percentage) of each monoterpene was expressed as a percentage of total monoterpenes (monoterpene profiles), while each sesquiterpene was calculated as a percentage of total monoterpenes plus sesquiterpenes (terpene profiles).

Headspace Gas Chromatography/Mass Spectrometry (HS-GC/MS) was then performed on a GC/MS system (Perkin Elmer Italia S.p.A., Milano (MI), Italy) composed of a GC AutoSystem XL coupled to a TurboMass mass spectrometer and combined with a TurboMatrix 40 automatic headspace sampler. The gas chromatograph was equipped with the column described above, operating with helium as a carrier gas at a constant flow of 3 mL min−1. The oven program was as follows: the initial temperature was 40 °C for 3 min, then a ramp of 1 °C min−1 brought the final temperature to 200 °C. The inlet temperature was 200 °C. The mass spectrometer was operating with an electron ionization of 70 eV, scanning the mass range from 35 to 350 m/z. Ion source temperature was 200 °C. The GC/MS control and data elaboration were performed by Perkin-Elmer Technologies TurboMass ver. Chemstation software. The mass spectrometer was calibrated using perfluorotributhylamine, as the calibration standard, with the Chemstation software.

Headspace gas chromatography (HS-GC) analyses were performed using the following conditions: He (carrier gas) at 3 mL min−1, pressurization time, 5 min, injection time set at 0.05 min to minimize peak broadening, thermostatting temperatures 80 °C, thermostatting times 30 min.

The MS spectral database (Wiley library) confirmed the elution sequence of the rosemary terpenes obtained by comparing the retention times of recorded peaks with those obtained by injecting pure compounds.

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