Isq mass spectrometer

The analysis of volatile constituents from the HD and nanoemulsions of S. satureioides essential oil was performed using a GC–MS apparatus. A trace GC ultra-chromatography system equipped with an ISQ-mass spectrometer and a 60 m × 0.25 mm × 0.25 μm-thick TG-5MS capillary column (Thermo Scientific, Waltham, MA, USA) was programmed from 50 °C with a holding time of 3 min, and then the temperature was increased at a rate of 4 °C per min to 140 °C with a holding time of 5 min. Consequently, the temperature was increased at a rate of 6 °C per minute to 260 °C for a 5-min isothermal holding time. The injector temperature was 180 °C, the ion source temperature was 200 °C, and the transition line temperature was 250 °C. The carrier gas was helium with a constant flow rate of 1.0 mL min⁻¹. The mass spectrometer had a scan range from m/z 40–450, and the ionization energy was set at 70 Ev. The identification of compounds was based on matching with the MS computer library (NIST library, 2005 version) and comparison with those of authentic compounds and published data [3 (link),4 (link),5 (link),10 ,16 ]. The relative percentage of the identified constituents was calculated from the GC peak areas, and Kovats index was calculated for each compound using the retention times of a homologous series of C₆–C₂₆ n-alkanes and by matching with the literature [16 ].

A 200 μl aliquot of the aqueous layer was dried down completely under N₂ (g). The dried samples were resuspended in 50 μl of pyridine containing 25 mg/ml of methoxyamine hydrochloride (Sigma), incubated at 60°C for 45 min, vigorously vortexed for 30 s, sonicated for 10 min, and incubated for an additional 45 min at 60°C. Next, samples were cooled to room temperature and briefly centrifuged. Then, 50 μl of N‐methyl‐N‐trimethylsilyltrifluoroacetamide with 1% trimethylchlorosilane (MSTFA + 1% TMCS, Thermo Fisher Scientific) was added and the samples were vigorously vortexed for 30 s and then incubated at 60°C for 30 min. Metabolites were separated and detected using a Trace 1310 GC coupled to an ISQ mass spectrometer (Thermo Fisher Scientific). Samples (1 μl) were injected at a 10:1 split ratio onto a 30 m TG‐5MS column (0.25 mm i.d., 0.25 μm film thickness; Thermo Fisher Scientific) with a 1.2 ml/min helium gas flow rate. The gas chromatography inlet was held at 285°C. The oven program started at 80°C for 30 s, followed by a ramp of 15°C/min to 330°C, and an 8‐min hold. Masses between 50–650 m/z were scanned at 5 scans/s under electron impact ionization. Transfer line and ion source were held at 300 and 260°C, respectively.

In citrus fruit, volatile compounds are mainly accumulated in the oil glands of the peel [38 (link)]. Thus, citrus peel was used for volatile compound extractions. In accordance with Liu et al. [21 (link)], 3 g of peel powder was extracted in 15 mL MTBE containing 400 μg of methyl nonanoate as an internal standard. The extraction was carried out in an ultrasonic cleaner FS60 (Fisher Scientific, Pittsburgh, PA, USA) for 1 h and the supernatant was collected and concentrated to 1.4 mL under a gentle N₂ stream.
An aliquot of 1 μL was analyzed by TRACE GC Ultra GC coupled with an ISQ mass spectrometer (Thermo Fisher Scientific, Waltham, MA, USA) and equipped with a TRACE^TM TR-5 MS column (30 m × 0.25 mm × 0.25 μm, Thermo Scientific, Bellefonte, PA, USA). The temperatures of the injection port, ion source, and MS transfer line were maintained at 250, 260, and 280 °C, respectively. Helium was used as a carrier gas with a split ratio of 50:1 at 1 mL/min. The column temperature program was initiated with 40 °C for 3 min, followed by a ramp of 3 °C/min until 160 °C for 1 min, then at a rate of 5 °C/min until 200 °C for 1 min, and finally, the temperature was raised to 240 °C at a rate of 8 °C/min and maintained for 3 min. The m/z range of the MS scan was from 45 to 400 in positive electron ionization mode at an ionization energy of 70 eV.

The analyses were performed using a trace 1300 series GC ultra gas chromatograph (Thermo Scientific). The chromatographic separation was performed on a “BPX70” cyanopropyl polysilene–siloxane based capillary column (30 m × 0.25 mm i.d., 0.25 mm) from SGE. The GC was interfaced with an ISQ mass spectrometer (Thermo Scientific). Compound identification and corresponding structural formulae were assigned using the National Institutes of Standards (NIST) library.