Table 4.

Methods based on use of fat retainers for n-alkane determination in vegetable oils.

Sample Amount—Internal Standard (I.S.)	Column Chromatography	Analysis (Injection Mode)—Column Type—Chromatographic Conditions	Ref.
100 mg oil sample in 5 mL hexane + I.S. mixture	A glass column (46 cm3) filled with silica gel heated al 550 °C for 18 h, pre-washed with 100 mL of hexane. After the sample was loaded, the n-alkane fraction was eluted with hexane (100 mL) and concentrated to 150 µL, followed by HPLC separation from aromatics on a 25 × 0.46 cm Lichrosorb Si-60, 5 µm.	GC-FID (on-column injection). Fused silica capillary column (25 cm × 0.25 mm i.d.), coated with 0.33 µm film of Ultra 1. Oven temperature: 60 °C (3 min) to 280 °C at 4 °C/min and held at this temperature until the end of the run. Injector and detector: 300 °C; carrier gas: nitrogen.	[24]
500 mg of oil sample + I.S. mixture in 5 mL of isohexane	A glass column (2.0 cm i.d. × 11cm) filled with silica gel heated at 550 °C for 18 h and deactivated with 1% water, was washed with iso-hexane (100 mL). After loading the sample, the n-alkane fraction was eluted with isohexane (130 mL) and concentrated to 0.3 mL. Followed HPLC separation from aromatics on a 25 × 0.46 cm Lichrosorb Si-60, 5 µm.	GC-FID (on-column injection). Fused silica capillary column (25 cm × 0.25 mm i.d.), coated with Ultra 1, 0.33 µm film thickness. Oven temperature: 60 °C (3 min) to 280 °C at 4 °C/min and held at this temperature until the end of the run. Injector and detector: 300 °C; carrier gas: nitrogen.	[5]
60 mg of oil sample + I.S. (n-C13, C14:1) in pentane	Online LC-GC-FID.	LC column: silica (Spherisorb), 100 × 4.6 mm i.d; wire interface; GC column: fused silica capillary column (12 m × 0.25 mm i.d.), coated with immobilized PS-255, 0.3 µm of film thickness. Transfer occurred at 49 °C; 8 min after the transfer the temperature was programmed at 15 °C/ min to 320 °C. The carrier gas (helium) inlet pressure was 70 kPa.	[11]
75 mg of oil sample + I.S. (n-C15) in 0.5 mL of hexane	A glass Pasteur pipette (145 mm × 9 mm, packed with activated silica gel, was loaded with the sample and eluted with 5 mL of hexane. Each oil sample was extracted twice, and the eluents were combined and concentrated to 0.5 mL.	GC-FID (splitless mode) GC. Fused silica capillary column (30 m × 0.32 mm), coated with DB-5, 0.25 µm film thickness. Oven temperature: 50 °C (1 min) to 150 °C at 20 °C/min, then to 230 °C (10 min) at 8 °C/min. Injector: 300 °C; detector 280 °C; carrier gas: helium (1.2 mL/min). As an additional tool for [12], stable carbon and hydrogen isotope analyses of n-alkanes were performed using an isotope ratio mass spectrometer interfaced with GC.	[12,28]
1 g of oil sample + I.S. (n-C15)	A glass column (1.5 cm i.d. × 50 cm) was filled with 40 mL hexane. About 18.5 g of silver-silica gel was poured slowly, avoiding bubbles. Later, a 1 cm layer of anhydrous sodium sulfate followed by a 1 cm layer of washed sand was added. Finally, the remaining solvent above the sand was discarded. After the sample was loaded, saturated hydrocarbons were eluted with 55 mL of hexane, concentrated and re-dissolved in 1 mL of heptane.	GC-FID (PTV). Fused silica capillary column (10 m × 0.32 mm) coated with CP-9070, 0.10 µm film thickness. Oven temperature: 60 °C (1 min) to 288 °C at 12 °C/min, then to 340 °C (4 min) at 6 °C/min. Detector temperature: 350 °C. Injection temperature program: 70 °C (1 min) to 300 °C (1 min) at 200 °C/min, and then back to 70 °C. Carrier gas: hydrogen at 15 mL/min.	[34]