Abstract
The results of the quantitative determination of fatty acid methyl esters of vegetable oils, (soybean, flaxseed, and palm oils) by eight basic and acid catalysis esterification methods were compared. The selected methods were described by Metcalfe, 1966 (MET, ref. 17); Bannon, 1982 (BAN, ref. 18); Joseph and Ackman, 1992 (JAC, ref. 3); Hartman and Lago, 1973 (HLA, ref. 19); Jham, 1982 (JHA, ref. 20); ISO 5509, 1978 (ISO, ref. 21); Bannon, 1982 (BBA, ref. 15) and Schuchardt and Lopes, 1988 (SLO, ref. 22). Despite the large variation in the determination of unsaturated fatty acids, all the methods were efficient in the analysis of saturated fatty acids. The results obtained show that fatty acid analysis may be affected by oil composition and that JAC, ISO, and BBA methods are more efficient. ISO, and BBA are recommended for low acidity samples due to their low reagent toxicity and cost. The JAC method is recommended only for high acidity samples, as the ISO and BBA methods are carried out in basic medium and cannot analyze the free fatty acids.
Highlights
Advancements in gas chromatography (GC) have furthered the study of lipids and provided knowledge on fatty acid composition in a short span of time
This comparative study evaluated commonly used esterification methods applied to different vegetable oils to determine the most adequate one in relation to analysis frequency, reagent consumption and toxicity, the cost‐benefit ratio, and the amount of fatty acid methyl esters (FAME) determined in the analyzed oils
Saturated FAME was used to verify the analysis optimization. It is recommended the use of theoretical factors in quantitative determinations of polyunsaturated fatty acids.[28]
Summary
Advancements in gas chromatography (GC) have furthered the study of lipids and provided knowledge on fatty acid composition in a short span of time. Several researchers investigate esterification procedures in search of an efficient method to obtain fatty acid methyl esters (FAME). These studies have been supported by advances in gas chromatography. The addition of an internal standard has been used in the analysis of fatty acid. This method is less sensitive to errors as the internal standard and the sample are injected together. It allows expressing fatty acid results in weight.[5,6,7]
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