Model 5975c mass spectrometer

The essential oil from dried powdered Thymus algeriensis aerial parts was isolated by steam distillation in a Clevenger-type apparatus according to Procedure III of the Yugoslav Pharmacopoeia IV [23 ]. Essential oil yield was 2.3% (w/w). Freshly isolated essential oil was a yellow liquid with an intense, necrotic odor.
Samples of 1 μl (dilution in hexane 10%) were subjected to analysis by GC-MS. GC analysis was performed on a model 7890 A (series II) gas chromatograph, with a flame ionization detector (FID) and a split ratio of 1:50 using a fused silica capillary column, HP5-MS (30 m × 250 μm i.d., 0.25 μm film thickness). Injector or detector temperature for each analysis was about 250°C, and the carrier gas was helium with a flow rate of 0.8 ml/min. Peak areas were measured by electronic integration, and relative amounts of the individual components were based on the peak areas. GC-MS was carried out on an Agilent model 5975 C mass spectrometer operating at ionizing energy mode at 70 eV, combined with the GC described above.

For the silylation derivatization method, 5 mg of extract was weighed into a glass tube and mixed with 50 µL of pyridine plus 75 µL of bis—(trimethylsilyl) trifluoracetamide (BSTFA). The mixture was sealed and heated at 100 °C for 60 min. Subsequently, the residue of the solvent was evaporated and dissolved in 500 µL of hexane. One microlitre of the final solution was injected into the GC–MS instrument. For the analysis, a gas chromatograph 6850 network GC system (Agilent Technologies, Santa Clara, CA, USA) was coupled to a Model 5975 C mass spectrometer equipped (Agilent Technologies) with an HP-5MS column that was 30 m in length, 0.25 mm in internal diameter and 0.25 µm in thickness (Agilent Technologies). The programmed temperature was varied from 100 to 300 °C with an increase rate of 5 °C/min, and helium was used as the carrier gas with a run flow rate of 0.7 mL/min. Injection was conducted in split mode with a split ratio of 1:20 and an injector temperature of 280 °C. The range of detected masses was m/z 35–600 with an ionization voltage of 70 eV and an interface temperature of 300 °C. The total running time was 40 min. 1—Octene and octadecane (Sigma—Aldrich; St. Louis, MO, USA) were injected as hydrocarbon standards [86 (link)].

The ethanolic extract was analyzed by gas chromatography‒mass spectrometry using a Model 6850 chromatograph (Agilent Technologies, Santa Clara, CA, USA) coupled with a Model 5975C mass spectrometer (Agilent Technologies) and HP-5MS column (30 m × 0.25 mm, 0.25 μm Agilent Technologies).
The ethanolic extract sample (1 µl of the sample from a solution of 1 mg/ml) was injected in split mode. The initial temperature was 70 °C for 2 min followed by one heating ramp up from 15 °C min⁻¹ to 290 °C and then maintained for 6 min. Helium was the carrier gas. The total analysis time was 31.0 min. The detected mass range was 35–600 m/z, the sample was ionized by electronic impact at 70 eV, and the ionization source temperature was 230 °C. The compounds were identified by comparison with the NIST version 8.0 library database (National Institute of Standards and Technology, Gaithersburg, MD, USA).