Gc 6890

Measurements were carried out on a gas chromatograph-mass selective detector (Hewlett Packard GC 6890, HP MSD 5973) equipped with an automatic injector unit. The injection volume was 1 µL in splitless mode with helium (6.0) as a carrier gas at a flow rate of 1 mL/min. For the M. brassicae and O. nubilalis samples, a RESTEC (Rxi-5SI) column (0.25 mm internal diameter × 30 m and 0.25 µm film thickness) was used. The GC separation conditions were as described in Moustafa et al. [80 (link)] for M. brassicae and Fodor et al. [32 (link)] for O. nubilalis. The selected ion monitoring (SIM) method was used, and calculations were performed with MSD ChemStation ver. D.01.02.16. For S. littoralis samples, the same GC-MS unit was used, but with an Agilent J&W VF WAXms (60 m × 0.25 mm × 0.25 µm) polar capillary column. Running conditions were as described by Moustafa et al. [81 (link)]. Authentic standards were initially injected in scan mode. The SIM method was used for both quantitative mass spectrometric detection and to confirm compound identity by utilizing the NIST 17 mass spectral database. For quantitative evaluation, Mass Hunter Workstation Quantitative Analysis B.09.00 was used.

A 1 μL aliquot of each sample was injected via an automatic splitless mode into a GC-MS unit (Hewlett Packard GC 6890, HP MSD 5973) equipped with a RESTEC (Rxi-5SI) column (0.25 mm internal diameter × 30 m and 0.25 μm film thickness) using helium (6.00) as a carrier gas at a flow rate of 1 mL/min. The running and heating conditions used were as described in Moustafa et al. [39 (link)] and Hull et al. [45 (link)]. The Selective Ion Method (SIM) was used for the rapid but sensitive fractionation of the main (Z11-hexadecenyl acetate) and minor (hexadecenyl acetate) pheromone components. Quantification was performed using MSD Chemstation ver. D.01.02.16. An authentic standard (E11-tetradecenyl acetate) was injected in scan mode to build the standard curve using Z11-hexadecenyl acetate and hexadecenyl acetate (Pherobank BV, The Netherlands) for six representative concentrations.

Gas chromatography experiments were carried out with a GC 6890 gas chromatograph coupled with a Hewlett Packard GC 5975B mass spectrometer (Agilent 5975B, Santa Clara, CA, USA). The GC-MS operation was performed according to the procedure described by (Chen et al., 2020 (link)). To obtain the resin component content, 0.05 g resin was dissolved in 0.5 mL of ethyl alcohol containing 50 µL tetramethylammonium hydroxide. The GC column temperature conditions were as follows: the initial column temperature was 60°C, held for 2 min, increased at 8°C min^-1 to 80°C, and reached a maximum of 280°C at a rate of 2°C per min for 5 min. The helium gas flow was set at 1 ml min^-1. The temperature of the injector was 260°C, and the volume was 1 µL with a 1/50 split ratio. Mass spectra were recorded under electron impact ionization at an electron energy of 70 eV in the range from m/z 30 to 600 along with solvent delay for 3 min.
Resin compositions were identified by matching experimental fragmentation patterns in mass spectra with the NIST08 database through the data processing system of Agilent Chem Station and then comparing with the relevant literature. Monoterpene and sesquiterpene content were determined by isobutylbenzene content, and diterpene content was determined by heptadecanoic acid content. We calculated the resin component content by comparing their peak areas.

Headspace Solid Phase Micro Extraction (SPME) was performed to collect and characterize the chemical composition of volatiles released from P. halepensis needles and roots (Jassbi, Zamanizadehnajari, & Baldwin, 2010). A SPME fiber coated with Polydimethylsiloxane/Divinylbenzene (PDMS/DVB, fiber diameter 65 μm, needle size 24 ga, StableFlexTM) was exposed for 4 hr to 10.0 g DM of suspended plant material in each microcosm 1 hr after the pine material was put into the microcosm (Figure 1). The SPME fibers were analyzed on a Hewlett‐Packard GC6890 coupled with a HP5973N Mass Selective Detector and equipped with a HP‐5MS capillary column (30 m × 0.25 mm × 0.25 µm, J&W Scientific). Data were acquired in scan mode from 40 to 300 uma. Retention indexes of compounds were determined relative to Wisconsin Diesel Range Hydrocarbon injection (C8‐C20, Interchim) and compared with those reported in the literature (Adams, 2007). The identification of some terpenes was done by comparison of mass spectra (MS) to those of reference standards (Sigma‐Aldrich®, Appendix 1). Database searches in the NIST 2014 mass spectral library were also conducted to tentatively annotate unidentified components.