5977b mass selective detector

GC-MS analysis was performed using an Agilent 7890 B gas chromatograph equipped with a 5977B mass selective detector (GC/MSD) (Agilent Technologies, Santa Clara, CA, USA). Chromatographic separation was achieved using a Rxi-5HT capillary column (30 m × 0.25 mm I.D., 0.25 μm film thickness; RESTEK, Bellefonte, PA, USA). An autosampler (Agilent Technologies; 7683B) was used for all experiments. The temperature of the injector was 280 °C. Using split mode, 1 µL of each extract was injected at a ratio of 1/50. The carrier gas was helium C-60 at a constant flow rate of 1 mL/min. The GC oven temperature was initially 60 °C for 1 min, increased to 160 °C in 3 °C/min increments, and then increased to 320 °C in 10 °C/min increments, followed by a hold for 10 min. The mass spectrometer used the electron ionization mode at 70 eV with the ion source temperature set at 250 °C. The running time was 30 min. Scan mode was used in the range of 30–600 m/z with a scan rate of 2.6 scan/s. Agilent Mass Hunter Qualitative Analysis B.04.00 software was used for data analysis. Single compounds were identified by comparing mass spectra with NIST mass spectral libraries (National Institute of Standards, 2020 version) and the Wiley Registry 12th Edition.

The GC/MS analysis was performed on an Agilent 7820A GC System Plus gas chromatograph coupled with 5977B Mass Selective detector and flame-ionization detector (Agilent Technologies, Palo Alto, CA, USA). A fused silica capillary column, a mid-polar DB-17HT (J&W Scientific, Folsom, CA, USA) with 60 m column length, 0.25 mm i.d., 0.25 μm film thickness, was used. The oven temperature was programmed from 60 °C (2.5 min held) to 100 °C at a rate of 5 °C/min, from 100 to 225 °C at a rate of 2.5 °C/min and from 225 to 275 °C at a rate of 5 °C, 10 min held at the final temperature was applied. Helium (99.999%) was used as a carrier gas at a constant flow rate of 0.8 mL/min. The split ratio was 1:125, the inlet temperature was set to 260 °C and the transfer line temperature was 280 °C. Mass selective detector operated in electron impact ionization (EI) mode at 70 eV electron energy, the ion source temperature was set to 230 °C and the quadrupole temperature was 150 °C. The mass scan range was 45–1050 m/z.

GC–MS analysis was performed using an Agilent 7890 B gas chromatograph equipped with a 5977B mass selective detector (GC/MSD) (Agilent Technologies, Santa Clara, CA, USA). Chromatographic separation was achieved using a Rxi-5HT capillary column (30 m × 0.25 mm I.D., 0.25 μm film thickness; RESTEK, Bellefonte, PA, USA). An automatic autosampler (Agilent 7683B) was used for all experiments. The temperature of the injector was 280 °C. One microliter of each extract was injected in split mode with a ratio of 1/50. The carrier gas was helium C-60 at a constant flow of 1 mL/min. The GC oven temperature was initially 60 °C for 1 min, increased to 160 °C in 3 °C/min increments, and then increased to 320 °C in 10 °C/min increments, followed by a hold for 10 min. The mass spectrometer was tuned on electron ionization mode at 70 eV with the ion source temperature set at 250 °C. The running time was 30 min. Scan mode was used in the range of 30–600 m/z with a scan rate of 2.6 scan/s. The Agilent Mass Hunter Qualitative Analysis B.04.00 software was used for data analysis. Single compounds were identified by comparing mass spectra with NIST mass spectral libraries (National Institute of Standards, 2005 version) and the Wiley Registry 8th Edition.

Volatile compounds in the peel were extracted using the same method as non-volatiles, except dichloromethane (VWR, Pennsylvania, USA) was used as the extraction solvent instead of methanol. The chromatographic and spectrometric parameters were adapted from Goh et al. 2019 and operated on a 7890B GC system coupled with a FID and the 5977B mass selective detector (all from Agilent Technologies, California, USA) [22 ]. For each analysis, a 1 μL splitless injection was used, and 2-octanol (VWR, Pennsylvania, USA) was used as an internal standard. Spectra of compounds detected were matched against an in-house library and the NIST 14 library, and linear retention indices were determined using C7-40 alkane standards (Supelco, Pennsylvania, USA). Data analysis was carried out on the MSD Chemstation software (ver. F.01.03.2357) (Agilent Technologies, California, USA). PCA biplots were constructed using concentrations of key volatiles as well as volatiles categorised by functional group using RStudio (Version 1.3.1093) and accompanying packages (ggbiplot).