Split splitless injector

Essential oils from savory (Satureja montana L.) and thyme (Thymus vulgaris L.) were purchased as commercial preparations with 99% purity from Soave (Turin, Italy). The compositional analyses were performed using a gas chromatograph Shimadzu (Kyoto, Japan) GC-2010 Plus equipped with a mass spectrometer GCMS-QP (Shimadzu, Kyoto, Japan) and a split-splitless injector (Shimadzu, Kyoto, Japan) [17 (link)]. A 10% stock emulsion (10% essential oil, 88% sterilized water, and 2% Tween 20, Merck, Darmstadt, Germany) was prepared from each essential oil. Emulsions of 1%, 0.5%, and 0.1% (vol/vol) were prepared for each essential oil application by diluting the stock emulsion with distilled water. All the resultant emulsions were shaken for 30 s before application to ensure a homogeneous essential oil mixture.

The composition of CEOs was analysed by gas chromatography using a flame ionization detector (GC-FID) without any derivatisation. Before GC analysis, CEOS were diluted 10 mg in 1 mL chloroform. Analyses were carried out on a Shimadzu GC-2010 system equipped with an AOC-20i auto sampler, split/split less injector, and a FID detector (Shimadzu, Milan, Italy). Experimental conditions were as follows: The column was a fused-silica capillary column (SLB^™-5 ms, Supelco, Milan, Italy) coated with 5% diphenyl −95% dimethyl siloxane (30 m × 0.25 mm id × 0.25 μm d_f); the oven temperature increased from 50 up to 250 °C, with a rate of 3.0 °C min⁻¹; and the injection volume was 1.0 μL in the split mode (30:1). Helium was used as carrier gas at 30.1 cm s⁻¹ of linear velocity (u), with an inlet pressure of 99.8 kPa. The detector temperature was set at 280 °C. The hydrogen flow rate was 50.0 mL min⁻¹; the air flow rate was 400 mL min⁻¹; and the make-up flow rate (N₂/Air) was 50 mL min⁻¹. The identification of the compounds was based on the comparison of their retention times with those of authentic standards available in our laboratory. The quantification of each compound identified in CEOs was performed using the peak area normalization and the results were expressed as the means of three experiments.