J w gc column

The cholesterol in yolk samples was determined using a Perkin-Elmer gas chromatograph (Shelton, MA, USA) according to AOAC [35 ]. Dried yolk samples (65 °C) were saponified with methanolic KOH solution (50 mL) in a water bath for 1 h. Next, the samples were treated with petroleum ether, concentrated on a rotary evaporator, and brought to neutral pH with distilled water. After removing the petroleum ether, the residue was treated with chloroform (5 mL). Aliquots of 1 μL of the obtained extracts were injected into an HP-5 GC fused silica capillary column (30 m × 0.32 mm ID, 0.1 µm film thickness; J&W GC Columns, Agilent, Santa Clara, CA, USA) and analyzed on a detector with flame ionization (FID). Cholesterol was identified by comparing the peak areas with those obtained from the laboratory standard solution. The cholesterol concentration is expressed as g/100 g yolk.

For FA determination, we used a Perkin Elmer–Clarus 500 gas chromatograph (Boston, MA, USA), fitted with a flame ionization detector (FID) and capillary separation column with high polar stationary phase Agilent J&WGC Columns (Santa Clara, CA, USA), DB-23 with dimensions of 60 m × 0.250 mm × 0.25 μm, as previously described by Hăbeanu et al. [31 ].

Automated sampling of amino acid derivatives was conducted using a Trace 1310 GC (Thermo Scientific) in combination with a TriPlus RSH autosampler (Thermo Scientific). A sample volume of 0.1 μl was injected into an injection port held at 240°C in splitless mode onto a capillary column (DB‐35, 30 m × 0.320 mm ID × 0.50 μm film thickness, Agilent J&W GC Columns). The GC oven temperature program for a single injection is detailed in Appendix S2.
All eluting compounds off the column were oxidized inside a GC Isolink II (Thermo Scientific) combustion interface containing a reactor held at 1,000°C. Water was removed through a Nafion membrane downstream of the reactor while CO₂ was cryogenically trapped in tubing submerged in liquid nitrogen before transfer to the IRMS (DELTA V; Thermo Scientific) through a Conflo IV (Thermo Scientific) universal interface.
High purity N₂ (>99.9997% N₂, Airgas) was used as reference gas to initially calculate the isotopic composition. Raw data were drift‐corrected (for drift correction procedure see Appendix S3). Average precision across all amino acids was 0.33‰. Individual precision of each amino acid is given in Appendix S4.

Cholesterol content of dried yolk samples (65 °C) was determined using a gas chromatograph Perkin-Elmer Clarus 500 (Shelton, MA, USA) according to AOAC Official Method 994.10: Cholesterol in foods [40 ]. The egg yolk samples were subjected to saponification using 50 mL of methanolic KOH solution (0.5 M) for one hour in a water bath. The next step is the extraction of cholesterol in petroleum ether, followed by concentration in a rotary evaporator and wash with distilled water to neutral pH. After removing the petroleum ether, the residue was taken up again with 3–5 mL of chloroform. Cholesterol was separated on a HP-5 GC capillary column (30 m × 0.32 mm id, 0.1 µm film thickness), Agilent J&W GC Columns, USA and detected on a flame ionization detector (FID). An 1 μL aliquot was injected in the GC column. Concentrations were calculated by comparing peak areas with those obtained from the standard solutions and were expressed as g cholesterol/100 g dried egg yolk.

Material test discs for studying leaching of eugenol were made using teflon rings (d = 8 mm, h = 2.8 mm). Test discs were immersed in sterile Milli-Q water (3 ml/disc) and kept at 37 °C. Every week for 18 weeks the water was changed and the amount of eugenol was analysed in the aliquot removed after week 1, 4 and 18.
Gas chromatography–mass spectrometry (GC-MS) was used to perform quantification of eugenol in the aliquots [Agilent Technologies 780 A GC System-5975 Series- with a mass selective detector, model number 63170 A with a HP 5MS UI column installed (Agilent J&W GC Columns, Santa Barbara, CA., USA)].
Five, individually prepared, samples of eugenol of known concentration (Sigma Chemical Co., St. Louis, MI, USA) , together with an internal standard were analysed at 150 °C for 6 min. The MS Scan parameters were set to 40–600 m/z. Linear regression was used to establish the calibration curve in the range (6–90) µg/ml. The calibration curve had a correlation coefficient of 0.998 without forcing zero. The MS limit of quantification of eugenol was 0.1 µg/ml.

Analyses of the oils were carried out on a GC-MS Thermo-Electron model Focus DSQ II (Thermo Fisher Scientific, Waltham, MA, USA), under the following conditions: DB-5ms (30 m × 0.25 mm; 0.25 mm film thickness) fused-silica capillary column (Agilent J&W GC Columns, Santa Clara, CA, USA); programmed temperature, 60–240 °C (3 °C/min); injector temperature, 250 °C; carrier gas, helium, adjusted to a linear velocity of 32 cm/s (measured at 100 °C); injection type, split (1.0 μL), from 1:1000 hexane solution; split flow was adjusted to yield a 20:1 ratio; septum sweep was a constant 10 mL/min; EIMS, electron energy, 70 eV; temperature of the ion source and connection parts, 200 °C. The quantitative data regarding the volatile constituents were obtained by peak area normalization using a FOCUS GC/FID (Thermo Fisher Scientific, Waltham, MA, USA) operated under similar conditions for the GC–MS, except the carrier gas, which was nitrogen. The retention index was calculated for all the volatile constituents using a homologous series of n-alkanes (C₈-C₃₂, Sigma–Aldrich, St. Louis, MO, USA), according to Van den Dool and Kratz (1963) [21 (link)].

DEL was determined with an Agilent Technologies 7890B GC coupled to an ECD detector. The quantitative analysis was done on an HP-5 column (30 m × 0.320 mm × 0.25 μm film thickness, Agilent J&W GC columns). The oven temperature program was ramped from 100°C (2 min hold time) to 270°C at 6°C/min with a hold time of 10 min. The injection and detector were at 250 and 300°C, respectively. The nitrogen carrier gas was maintained at a flow rate of 1.0 mL/min. A sample of 1 μL was injected in splitless mode.
Percentages of DEL in the bioaccessible fraction (%) were calculated as follows: BIO × 100/BD, where BIO is the DEL amount detected in the bioaccessible fraction and BD is the DEL amount detected in the same sample before digestion.