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Direct methylation of long‐chain fatty acids in feeds, digesta and faeces without prior extraction
Author(s) -
Outen George E.,
Beever David E.,
Fenlon John S.
Publication year - 1976
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740270505
Subject(s) - saponification , chemistry , chromatography , methylation , extraction (chemistry) , saponification value , hexane , fatty acid , gas chromatography , fatty acid methyl ester , organic chemistry , biochemistry , biodiesel , gene , catalysis
Four feeds, two duodenal digesta samples, two ileal digesta samples and two faecal samples were analysed in quintuplicate for their long‐chain fatty acid content by a new method (direct methylation) whereby the dried samples were heated with benzene and 5% w/v methanolic HCl in screw‐capped bottles at 70°C for 2 h. The methyl esters, were extracted with hexane, purified by thin‐layer chromatography, and measured by gas–liquid chromatography. The values obtained were compared with those obtained using an established method (saponification) in which the dried samples were refluxed with ethanolic KOH, the fatty acids liberated by acidification, extracted and methylated by refluxing with 5% w/v methanolic HCl and the methyl esters extracted, purified and measured as before. Statistical analysis indicated no particular bias for either method though in general the direct methylation appeared to have a lower variance than saponification. A regression analysis of the direct methylation means ( d ) against the saponification means ( s ) gave the equation:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} \mathop d\limits^ - = 0.0073{\rm + 0}{\rm .988 }\mathop s\limits^ - {\rm = }r^2 = {\rm 0}{\rm .994 (}n{\rm = 96)} \\ {\rm (} \pm {\rm 0}{\rm .0255) (} \pm {\rm 0}{\rm .0079)} \\ \end{array} $$\end{document} .