Table 1.

The application of GC-FID and GC-MS for analysis of ω-3 and ω-6 FAs in fish oils contained in numerous products.

ω-3 and ω-6 FAs (Samples)	Sample Preparation	GC Condition	Results	Ref.
ALA and DHA in mackerel fish oil	The fish was subjected to boiling, and the separated oils were extracted using ethanol-chloroform. Fish oils were subjected to derivatization to provide FAMEs with BF3.	Capillary column with DB-5 stationary phase (30 m × 0.32 mm, 0.25 μm film thickness), carrier gas: helium; splitness; oven was programmed at temperature 160–200 °C with flow rate 1.0, detector FID and the injector temperatures were set at 250 °C.	APA and DHA were well separated with good efficiency as indicated with low high equivalent theoretical plate. The recovery obtained was in the range of 100.36 ± 0.31 (APA) to 100.58 ± 0.32. The levels of APA and DHA found were 0.181–0.214% (APA) and 0.010–0.321%.	[51]
EPA and DHA in fish oil capsules	The fish oil was taken from fish oil capsules then used for derivatization of the polyunsaturated fatty acids into FAMEs.	Capillary column of nitroterephthalic acid-modified polyethylene glycol, PEG bonded (30 m × 0.32 mm ID × 0.25 µm), carrier gas: helium, oven temperature was programmed at temperature of 100–240 °C with total running time of 38 min using flow rate of 0.8 mL/min; injector temperature was 240 °C in split mode (20:1); the detector temperature (ion trap mass spectrometer) was 240 °C.	The combined concentrations of EPA and DHA ranged from 160.6–360.4 mg/g, with an average result of 197.3 ± 50.7 mg/g. The limit of detection and limit of quantification were 0.16–0.18 mg/g and 0.46–0.63 mg/g, respectively, with recoveries above 76%.	[52]
EPA and DHA in fish oil capsules	The fish oil from fish oil capsules was pipetted, weighed, and subjected to derivatization to form FAMEs using BF3.	Capillary column of RTX-5SM (60 m × 0.25 mm, layer thickness 0.25 μm), carrier gas: helium with flow rate of 0.73 mL/min, oven temperature was programmed from 80–280 °C, injector temperature was 250 °C with split ratio 1:200, the temperature of the electron impact source was set at 200 °C	The EPA and DHA in fish oil capsules were determined in relative areas. All tested products had relative content of EPA and DHA in accordance with the respective labels.	[53]
EPA and DHA in fish oil nutritional capsules	The fish oil nutritional samples were subjected to derivatization to obtain FAMEs using BF3.	A DB5-MS capillary column (30 m × 0.32 mm ID × 0.25 µm) was used, carrier gas: helium (0.8 mL/min), oven temperature was programmed at 80–280 °C, injector temperature was 250 °C with a split ratio of 10:1, ion source temperature of EI was 200 °C.	The GC-MS method had good sensitivity, accuracy, and precision. The LoDs for EPA and DHA were 0.08 ng and 0.21 ng, respectively. The content of EPA was 39.52 to 509.16 mg/g, and the content of DHA was 35.14 to 645.70 mg/g. The obtained recovery was 100.50% and 103.83% for EPA and DHA, respectively, with RSD less than 1.05% for both EPA and DHA.	[49]
EPA and DHA in fish	Fish samples were divided into three groups: raw, baking, and steaming. The fat content was extracted using the Bligh and Dyer method. The obtained fats were then subjected to derivatization to provide FAMEs using BF3.	A capillary column with high polarity of GC HP-88 (60 m length, 0.25 mm ID, 0.2 µm DF) was used, carrier gas: helium with flow rate of 1 mL/min, the oven temperature was programmed from 40 °C to 230 °C, the temperature of the injector was 250 °C with a split ratio of 20:1, the FID temperature was 250 °C.	The method could separate EPA and DHA with good resolution. The method had a high accuracy shown by the recovery (>95%) and good precision (RSD ≤ 2%).	[48]
EPA and DHA in commercial omega-3 dietary supplements	Supplements of cod liver oils, algal oils, krill oils, and fish oils were subjected to derivatization to obtain FAMEs using BF3.	A capillary column of wax CP-52CB (CP 8843, 30 m × 0.32 mm I.D., DF-25 coating thickness 0.25 μm) was used. The oven temperature was programmed from 170–240 °C. Carrier gas was helium at a flow rate of 2.5 mL/min. The temperature of the injector was set at 250 °C, whereas FID was operated at 300 °C.	The contents of EPA and DHA for fish and krill-based supplements were 81.8–456.4 mg/g oil and 51.6–220.4 mg/g oil, respectively. For algal oil, the content of EPA was 7.7–151.1 mg/g and the content of DHA was 237.8–423.5 mg/g oil.	[54]
EPA and DHA in South Pacific fish and shellfish species	Samples were subjected to total lipids extraction applying the Folch method then used for the derivatization of the fatty acids to obtain FAMEs using BF3.	Analysis was performed using GC-FID using programmed temperature with helium as the carrier gas.	Red cusk eel contained EPA and DHA levels of 40.8 and 74.4 mg/100 g, respectively. Mackerel contained 414.7 and 956.0 mg/100 g of EPA and DHA, respectively. Sea squirt (shellfish species) contained EPA and DHA levels of 375.0 and 165.7 mg/100 g, respectively. In addition, EPA + DHA content in Chilean abalone was 63.6 mg/100 g.	[55]
EPA and DHA in Irish microalgal isolates (three marine strains: diatom cf. Stauroneis sp. LACW24, chrophyte cf. Phaeothamnion sp. LACW34, and haptophyte Diacronema sp. GMC30)	The total lipids of microalgal isolates were extracted using the Bligh and Dyer method. The lipids were further processed and used in derivatization to obtain FAMEs using BF3.	A capillary column of BPX70 120 m length and 0.22 mm internal diameter was used. The oven temperature was programmed from 50–240 °C. The carrier gas was helium operated at 2 mL/min. The sample was injected at a split ratio of 100:1 at an injector temperature of 250 °C. The detector temperature of the MS source was set at 230 °C, and the MS Quad was at 150 °C.	The average yields of EPA were 3.9, 11.9, and 1.3 mg EPA/g DW for GMC30, LACW24, and LACW34, respectively. The average yields of DHA were 3.0 and 2.0 mg DHA/g DW for GMC30 and LACW34, respectively.	[56]
EPA and DHA in marine fish species in Turkish waters	The total lipids from twelve marine fish species in Turkey were extracted, and the fatty acids content was further derivatized to provide FAMEs.	A fused silica capillary column (25 m × 0.2 mm ID) was used, and the oven temperature was set from 170–300 °C. The carrier gas was hydrogen. The injector temperature was 250 °C, whereas the detector temperature (FID) was 300 °C.	DHA ranged from 43.7 to 75.2%. The n-3/n-6 FA ratio ranged from 2.67 to 12.61.	[57]
EPA and DHA in sardine oil	The lipids of sardine oil were subjected to derivatization to obtain FAMEs.	Analysis was performed using a capillary column (EC-wax, 30 m × 0.25 mm i.d.) at oven temperature programmed from 50 °C to 220 °C. The split ratio of sample injection was 100:1 with an injector temperature of 250 °C. The detector (FID) temperature was set at 270 °C.	The unhydrolyzed oil contained EPA and DHA levels of 26.86% and 13.62%, respectively. The hydrolyzed oil contained 33.74% EPA and 29.94% DHA.	[58]