Analysis of alpha-linolenic acid and docosahexaenoic acid in mackerel fish oil (Rastrelliger Kanagurta) using gas chromatography

Objective: This study aimed to obtain the levels of alpha-linolenic acid (ALA) and docosahexaenoic acid (DHA) in mackerel fish oil by pressing and extraction with solvent methods. Methods: The optimum conditions were determined, and validation methods were performed for a mixture of ALA and DHA to obtain a valid method for the determination of the levels of ALA and DHA in mackerel fish oil. Derivatization was performed by the Lepage esterification method using methanol:toluene 4:1 (v/v) and an acetyl chloride catalyst. Gas chromatography with the Shimadzu GC-17A with a DB-5 column and flame ionization detector was used to analyze samples at a column temperature of 200°C with an increase of 2°C/min up to 230°C (maintained for 20 min). Injector and detector temperatures of 250°C were used with a flow rate of 1.00 mL/min. Results: The retention time of ALA and DHA was 11.440 min and 22.337 min with a Tf of 0.949 and 1.006, respectively. The validation results fulfilled the acceptance criteria with r values of 0.99953 and 0.99934, respectively. Total levels of ALA and DHA in mackerel fish oil were 0.39521% by pressing and 0.33014% by extraction with solvents. Conclusion: This method could be used as an alternative method to analyze ALA and DHA level in fish oil.