Zb 5ms column

Chromatographic analyses were performed using an Agilent 7890B (Bydgoszcz, Poland), equipped with a split/splitless injector and multipurpose autosampler, and an Agilent 5977B mass-selective detector. The GC was fitted with a ZB-5-MS column (Zebron, Phenomenex Inc., Torrance, CA, USA), 30 m × 0.25 mm 0.25 µm, containing (5% phenyl)-methylpolysiloxane.
The injector port was held at 270 °C and used in the split mode (5:1), and 1 µL injections were made. The temperature program used for the analysis was as follows: 80 °C (2 min), ramped at 15 °C/min to 250 °C, and held for 15 min. Helium was used as the carrier gas at a flow rate of 1 mL min⁻¹.
Full-scan mass spectra were recorded with an m/z range of 50–400 in electron-impact mode at 70 eV.
The transfer line and ion source temperatures were set at 280 and 230 °C, respectively. The scan rate was 2.9 scan/s, with a cathode delay time of 5 min. The SCAN mode was used for identification of analytes.

Compounds were identified by gas chromatography-mass spectrometry (GC-MS) analysis. The mixture was separated using ZB-5ms column (Phenomenex) and then the single constituents were identified using GC-MS-QP2010 SE mass spectrometer (Shimadzu). The injection volume was 1 µL (split ratio 200:1) and the oven temperature profile was as follows: 50 °C for 2 min followed by an increase of 4 °C min⁻¹ to 280 °C; 280 °C for 2 min; an increase of 40 °C min⁻¹ to 320 °C; 320 °C for 5 min. Helium with the flow of 2 mL min⁻¹ was used as the carrier gas.

Volatile constituents were analyzed by Shimadzu GC-MS QP 2010 (Shimadzu Corporation, Kyoto, Japan) fitted with AOC 5000 autoinjector system, and operated in the EI mode at 70 eV, equipped with ZB-5MS column, (Phenomenex, USA). The following conditions were maintained: the initial temperature at 70°C for 3.0 min, ramped at 4.0°C/min to 220°C, and held for 5.0 min. Helium gas was used as a carrier at a flow rate of 1.05 mL/min. The sample volume 1.0 μL was injected in split mode ratio (1:10). The injector and detector temperature were set at 240°C and 250°C, respectively. The identity of each compound was assigned by comparing their relative retention index (RRI) relative to the n-alkane mixture (C₉-C₂₄). Compounds were also characterized by a comparison of their spectra with those available from MS libraries such as National Institute of Standards and Technology (NIST) database (McLafferty, 2000 ).

The Asteraceae essential oils were analyzed by GC–MS using a Shimadzu GC–MS-QP2010 Ultra fitted with a Phenomenex ZB-5ms column as previously described [104 (link)]. Identification of the essential oil components was determined by comparison of their retention indices, determined with respect to a homologous series of n-alkanes and their mass spectral fragmentation patters with those from available databases (Adams [105 ], NIST17 [106 ], and FFNSC 3 [107 ]) or in our in-house library [108 ].

Sesquiterpene quantification was performed with GC‐MS. The chloroform: methanol: acetone 2:1:0.5 (v/v/v) extracts were dried by passing them through a Pasteur pipette filled with anhydrous sodium sulphate (Sigma‐Aldrich). Samples were analysed on an Agilent 7890A gas chromatograph connected to a 5795C mass selective Triple‐Axis Detector (Agilent Technologies, United States). For that purpose, 1 μL of extract was injected at 250 °C in splitless mode on a ZB‐5MS column (Phenomenex, 30 m × 0.25 mm; ID 0.25 μm) with 5 m guard column with a constant flow of helium at 1 mL/min. The oven was programmed for 1 min at 45 °C and then subsequently ramped at 10 °C/min to 300 °C and kept for a final time of 5 min with a solvent delay of 5.5 min. The ionization potential was set at 70 eV, and scanning was performed from 45 to 400 atomic mass units, with a scanning speed of 3.99 scans/sec. Quantification was performed with an external calibration curve from α‐bisabolol (Sigma‐Aldrich). The Henry's law constants were calculated with the HENRYWIN program available online (https://www.epa.gov/tsca-screening-tools/epi-suitetm-estimation-program-interface) at 25 °C [HENRYWIN v3.10] Bond Method.

The hydrolysis reaction was performed according to a previous study [17 (link)]. Compound 3 or 4 (1 µg) was hydrolyzed with 40 µL of 2 mol/L TFA at 100 °C for 2 h. The hydrolysate mixture was concentrated to dryness in vacuo. The residue was trimethylsilylated with 50 µL of BSTFA + TMCS (99:1) at 70 °C for 3 h. The trimethylsilylated sample (2 µL) was subjected to GC-MS analysis. GC separation was carried out on a Zebron ZB-5MS column (30 m × 0.25 mm i.d., 0.25 µm film thickness, Phenomenex) under the following conditions: injector temperature, 280 °C; carrier gas, helium; and flow rate, 1.0 mL/min. The temperature program of the column oven was set to hold at 70 °C for 1 min, then increase at 10 °C/min to 300 °C, and finally hold at 300 °C for 3 min. The conditions used for the mass spectrometer were as follows: ionization mode, EI (70 eV); ion source temperature, 200 °C; scan range, m/z 61–760; and scan rate, 1 s/scan.