Agilent 5975c mass selective detector

GC-MS analyses were performed using Agilent 5975C mass selective detector coupled to a 7890A gas chromatograph (Agilent Technologies, Santa Clara, CA, United States) with 7693 autosampler and a DB-5MS DG capillary column (30 m plus 10 m Duraguard^®) with a diameter of 0.25 mm, film thickness of 0.25 μm (Agilent J &W, Santa Clara, CA, United States) as described by Mamer et al. (2013) (link). The GC-MS was run in electron ionization mode (70 eV) and Selected Ion Monitoring (SIM) mode. Data acquisition was done in Scan and SIM modes using MassHunter (Agilent) software. The spectra obtained were compared against the NIST (National Institute of Standards) database. The root samples had large amounts of malic and citric acids, and were diluted 1:40 before being run again in Scan mode. While root exudates did not require dilution. Data were represented as normalized area which is the area of peak divided by amount of sample in mg (roots) or μL (root exudates).

Relative abundances of essential oil components and esterified diterpene acids were studied using gas chromatography with mass spectrometric detection (GC-MS). GC-MS analyses were performed using an Agilent Technologies 7890A GC-System coupled with an Agilent 5975C mass selective detector (triple-Axis detector, Agilent Technologies, Wilmington, DE, USA). An autosampler unit (Agilent Technologies 7693-100 positions) held samples. Separation of 1-μL injections used an HP-5MS Agilent column (30 m × 250 μm × 0.25 μm). Operating conditions were as follows: injector split ratio 25:1, temperature 250 °C, carrier gas helium, 1.0 mL/min, and constant flow. Column temperature was 50 °C (no hold) and 5 °C per minute. Then, at 280 °C, it was held at 5 min. Mass fragmentation patterns were acquired at −70 eV using a mass scan range of m/z 30–400.
Primary identifications were performed by comparison of mass spectra with an electronic library database [54 ] and confirmed using arithmetic indices, calculated relative to n-alkanes, when compared with values published in Adams [55 ] by visual comparison against mass spectral images [55 ]. Semi-quantification was achieved by the GC-MS operating software, using data with a minimum peak area of 0.1%, by calculating the area under the curve.
HRESIMS spectra were recorded using an AB Sciex 5600 TripleTOF mass spectrometer in positive mode.

The EO was analyzed by an Agilent 6890 gas chromatograph (GC) equipped with a flame ionization detector (FID). Capillary column: HP-5MS (60 m × 0.25 mm, 0.25 μm film thickness). The injection volume was 1 μL and split injection was used (split ratio 1:20). The flow rate of carrier gas helium was set at 1 mL/min. The following GC oven temperature was used: kept at 70 °C (2 min), 2 °C per min to 180 °C (55 min), 10 °C per min to 310 °C (13 min), and held at 310 °C (4 min). The GC-MS analysis was carried out using an Agilent 6890 gas chromatograph equipped with an Agilent 5975C mass selective detector (Agilent Technologies Inc., CA, USA). GC column and parameters were the same as in GC-FID. The mass spectra operated in the mass range (m/z 29 to 500) and EI mode (70 eV). The interface temperature and ion source temperature were 280 °C and 230 °C, respectively. The relative percentage of chemical constituents was determined by the peak area. The retention index (RI) was determined by referring to a series of n-alkanes (C₈–C₂₁). The constituents of the EO were identified by comparison of their retention index and mass spectrum with those listed in NIST 2017 and Wiley 275 databases.