Zebron zb 5ms

The extraction of aroma volatile compounds was performed through the in-tube extraction technique (ITEX) and the analysis was carried out on a GCMS QP-2010 gas chromatograph-mass spectrometer instrument (Shimadzu Scientific Instruments, Kyoto, Japan) as described in our previous works [77 (link),78 (link)]. Briefly, 3 g of each sample was introduced into a headspace vial of 20 mL, incubated for 20 min at a temperature of 60 °C, and the volatile compounds in the gas phase were absorbed through a fiber syringe (ITEX-2TRAPTXTA, Tenax TA 80/100 mesh) and directly desorbed into the GC-MS injector.
A Zebron ZB-5MS (Phenomenex) capillary column was used for the separation of the volatile compounds with helium as the carrier gas, a split ratio of 1:5, and a flow rate of 1 mL/min. The chromatographic column program was as follows: 35 °C (for 5 min) rising to 155 °C with 7 °C/min and then heated to 260 °C with 10 °C/min and held for 5 min. NIST27 and NIST147 mass spectra libraries were used for identifying the spectra of the reference compounds and checked by comparison with retention indices drawn from www.pherobase.com or www.flavornet.org [79 ,80 ]. The peaks that were identified at least in two of the three total ion chromatograms (TIC) were considered in calculating the total area of peaks (100%) and the relative areas of the volatile compounds [44 (link)].

A TRACE gas chromatograph [18 (link)] with an ISQ™ mass spectrometer (MS) from Thermo Fisher (Waltham, MA, USA) was used. The chromatographic separations were conducted on a Zebron™ ZB-5MS (30 m × 0.25 mm i.d., 0.25 µm film thickness) from Phenomenex (Torrance, CA, USA). Helium at a flow rate of 1.43 mL/min was the carrier gas. The inlet temperature was 250 °C, the split ratio was 50:1, and the injection volume was 1 μL. The oven temperature was held for 4 min at 60 °C; then it was increased to 280 °C at a rate of 10 °C/min and held for 5 min; finally, it was ramped to 300 °C at a rate of 10 °C/min and held for 10 min. The following MS settings were used: m/z: 50 to 350 amu; ionization energy: 70 eV; transfer line temperature: 320 °C; and source temperature: 230 °C. The linear retention indices were determined for each peak using a C8–C20 standard mixture of n-alkanes and compared with those of the literature. Furthermore, the recorded mass spectral information was compared with that from the NIST11 database. All measurements were performed in triplicate.

Chemical trail and control extracts were concentrated to approximately 10 µl under gentle helium flow, and 2 µl were analysed by GC/MS. All injections were performed on a Clarus 600 GC/MS apparatus (Perkin Elmer Inc., Wellesley, PA, USA) equipped with a 30 m × 0.25 × 0.25 fused-silica capillary column (Zebron ZB-5MS, Phenomenex Inc., Torrance, CA, USA). Extracts were injected in splitless mode with the oven programmed at 100°C for 1 min, raised at 10°C min⁻¹ up to 180°C, maintained for 1 min and then 5°C min⁻¹ up to 280°C with 20-min hold. Injector temperature was set at 250°C and helium at 1 ml min⁻¹ was used as carrier gas. The detection was performed in EI mode at 70 eV with ionization source and the transfer line set at 180°C and 250°C, respectively. Scan mode was employed (m/z 35–500), and tentative identification was based on retention indices according to alkane standards and diagnostic ions reported in the literature, as there is no commercial sources for these cuticular hydrocarbons [35 (link)–39 (link)].

The analyses were performed on a TRACE gas chromatograph (GC) coupled to an ISQ™ mass spectrometer (MS) from Thermo Fisher (Waltham, MA, USA). The column was Zebron™ ZB-5MS (30 m × 0.25 mm i.d., 0.25 µm film thickness) from Phenomenex (Torrance, CA, USA); Carrier gas—helium; flow rate—1.43 mL/min; inlet temperature—250 °C; split ratio—50:1; injection volume—1 μL. The oven temperature was programmed as follows: 4 min held at 60 °C; then ramped up to 280 °C at a rate of 10 °C/min and held at 280 °C for 5 min; then ramped to 300 °C at 10 °C/min and held at 300 °C for 10 min. The MS was set in full scan mode from 50–350 amu, with the following parameters: ionization energy—70 eV; source temperature—230 °C; transfer line temperature—320 °C. Linear retention indices (LRI) were calculated for the individual compounds using a standard mixture of C8–C20 n-alkanes. The compounds were identified by comparing their mass spectra with those from the NIST 11 Mass Spectra Library and their LRI with literature data. Each analysis was performed in triplicate.

The technique was used for initial identification of analytes by comparing their retention characteristics and mass spectra with those of synthetic standards and for quantification of the FA-derived compounds. The following conditions were employed using a 6890N gas chromatograph (Agilent Technologies) coupled to a Pegasus IV D time-of-flight (TOF) mass selective detector (LECO Corp.): helium carrier gas, 250°C injector temperature, 1 mL.min⁻¹column flow, modulation time of 4 s (hot pulse time 0.8 s, cool time 1.2 s), modulator temperature offset of +20°C (relative to secondary oven) and secondary oven temperature offset of +10°C (relative to primary oven). Zebron ZB-5ms (30 m × 250 μm I. D. × 0.25 μm film thickness, Phenomenex) was used as a non-polar primary column and BPX-50 (1.5 m × 100 μm I. D. × 0.10 μm film thickness, SGE) was used as a more polar secondary column. The primary oven temperature program was as follows: 100°C (1 min), then a single ramp to 320°C at a rate of 4 °C.min⁻¹ with a final hold for 5 min at 320°C.
The mass selective detector was operated in electron ionization mode (electron voltage −70 V) with a transfer line temperature of 260°C, ion source temperature of 220°C, 100 Hz acquisition rate, mass scan range of 30–600 u and 1800 V detector voltage. ChromaTOF software (LECO Corp.) was used to collect and analyze the data.