Hp 6890 series gc

Moisture was measured by oven drying at 105 °C to a constant weight. Total lipids (TL) were extracted according to Folch [48 (link)] and determined gravimetrically. Fatty acids were transesterified to methyl ester (FAMEs) according to the procedure described by Prato [49 (link)]. FAMEs were analyzed by gas chromatography (GC) using an HP 6890 series GC (Hewlett Packard, Wilmington, DE, USA) equipped with a flame ionization detector. FAMEs were separated with an Agilent HP-88 column (60 m × 0.25 mm id, film thickness 0.25 µm) by Agilent Technologies (Santa Clara, CA, USA). Helium was used as the carrier gas at a flow rate of 1 mL/min. FAMEs were identified by comparing retention times with reference standards (Supelco 37 Component FAME Mix, and PUFA N° 1). The relative quantities of FAs were calculated as percentages (% of total FAs). Quantification (mg/100 ww) was made using methyl nonadecanoate (50 µg/mL) as an internal standard.

Chromatographic analyses were conducted using a Hewlett-Packard HP 6890 series GC/MS device. HP-5MS (5% phenyl methyl siloxane, 30 m × 250 μm × 0.25 μm) was used as the capillary column. Helium was used as the carrier gas, at a flow rate of 1.0 mL/min. The column’s initial temperature was 180 °C 1 min after injection. The temperature was increased to 250 °C with an 8 °C/min heating ramp and a 1 min hold time, and the temperature was increased to 300 °C, with a 2 °C/min heating ramp over 10 min. The injection was performed in split mode (split ratio: 10:1). For analysis, the interface temperature was 250 °C, the injector temperature was 280 °C, and the running time was 49 min. The MS scan range was m/z 20–1000 using electron impact (EI) ionization (70 eV) and an ion source temperature of 250 °C. The components were identified by the comparison of their mass spectra with those of Wiley 9 and the NIST library. The relative percentages of the separated compounds were calculated with total ion chromatography using the computerized integrator. The retention indices (RI) were recognized externally using a series of n-alkanes (C6–C22), under the same chromatographic conditions [24 (link)].

Hydrocarbon analysis was performed according to a previously established protocol [22 (link),29 (link),40 (link)]. Briefly, the samples were spiked with a mixture of deuterated standards (dodecane-d₂₆, hexadecane-d₃₄, naphthalene-d₈, phenanthrene-d₁₀ and pyrelene-d₁₂) and extracted three times with 15 mL dichloromethane. The extracts were combined and passed through a chromatographic column with 20 g anhydrous sodium sulfate to remove excess water. Finally, the extracts were concentrated by rotary evaporator to 500 μl.
Alkanes, polycyclic aromatic hydrocarbons (PAH), and alkylated PAHs were analyzed using HP-6890 Series GC (Hewlett Packard) interfaced with an Agilent 5973 inert mass selective detector (MSD), and operated in a selective ion monitoring (SIM) mode. The hydrocarbons were resolved in the Agilent DB-5MS column (30-m long, 0.25-mm I.D., 0.25-μm thick). The operating conditions were as follows: 40°C for 1 min, ramped at 20°C/min to 180°C, ramped at 5°C/min to 300°C and held for 28 min. The detection limit of the instrument was 2.5 μg/L and the surrogate recoveries varied between 55–112%. The hydrocarbons were quantified using the deuterated standards. Reported concentrations of target analytes were recovery-corrected. The efficiency of biodegradation was computed relative to the residual concentration in the sterile control as mentioned elsewhere [41 ].