Comparison of six methylation methods for analysis of the fatty acid composition of albacore lipid

Abstract
Summary: Six methods widely used to produce methyl esters for the gas chromatographic determination of the fatty acid composition of a marine lipid were compared. Four acid‐catalyzed methods (1% H2SO4: CH3OH; 5% HCl: CH3OH; 7% and 14% BF3: CH3OH) and two base‐catalyzed methods [0.5M NaOCH3: CH3OH; (1:4) tetramethylguanidine: CH3OH] were used.The use of BF3: CH3OH (7% and 14%) gave a lower content of 18:1 n9 than the other methods and produced an artefact (2.7–3.2% of total fatty acid content) eluting between the 20:5 and 24:1 fatty acid methyl esters. No significant differences were obtained between the other four methods.Accordingly the use of BF3: CH3OH for transmethylation of marine lipids is not recommended. Results obtained in the other four methods showed that all are comparable.

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