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Remarks on official methods employing boron trifluoride in the preparation of methyl esters of the fatty acids of fish oils
Author(s) -
Ackman R. G.
Publication year - 1998
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-998-0263-9
Subject(s) - saponification , transesterification , boron trifluoride , organic chemistry , chemistry , fish oil , methanol , fatty acid methyl ester , fish <actinopterygii> , biodiesel , catalysis , biology , fishery
Some “official methods” for preparing methyl esters of the fatty acids from oils or fats may be referred to by users as the boron trifluoride (BF 3 ) method and invariably have two stages. The first stage, brief treatment with alkali [commonly NaOH in methanol (MeOH), sometimes NaOCH 3 ] and heat has been popularly described as a saponification step for over 30 yr. In fact, the disappearance of visible fat or oil is mostly transesterification, which can be accomplished in a few minutes under mild conditions. Free fatty acids (FFA) originally present, or produced by saponification, are not converted to methyl esters at this stage. The second stage, heating in BF 3 ‐MeOH, has in practice been as short as 2 min. It can convert all FFA to methyl esters, but this step requires at least 30 min. Examples from the recent literature illustrate the necessity of extending the time for BF 3 ‐MeOH transesterification of lipids or oils and methylation of FFA. No alkali transesterification is needed.