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Fatty acids of cows' milk. A. Techniques employed in supplementing gas‐liquid chromatography for identification of fatty acids
Author(s) -
Magidman Paul,
Herb S. F.,
Barford R. A.,
Riemenschneider R. W.
Publication year - 1962
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/bf02632746
Subject(s) - degree of unsaturation , chemistry , chromatography , gas chromatography , polyunsaturated fatty acid , conjugated system , double bond , distillation , fatty acid , silicic acid , spectrophotometry , organic chemistry , polymer
Abstract Milk fat methyl esters were subjected to distillation and silicic acid column chromatography to provide fractions of less complexity for gas‐liquid chromatographic analysis. It was still necessary however to employ supplemental techniques for identification. Chromatograms were obtained with polyester columns of different polarity on all the fractions and necessary reference samples. While many of the components were identified in the usual way by plots of relative retention time versus number of carbon atoms, iodine values for total unsaturation and ultraviolet spectrophotometry for conjugated and nonconjugated polyunsaturated acids were essential for positive identification of some components. Similarly, examination by infrared spectrophotometry confirmed the presence or absence of conjugated diene as cis‐trans, trans‐trans or both. Isolated trans or terminal double bonds were also determined in this way. Gas‐liquid chromatograms of some fractions showed incompletely resolved peaks attributable to the presence of methyl esters of odd‐carbon atom, branched‐chain, and unsaturated acids. Hydrogenation and rechromatographing provided more positive determination of the structure of these components. Further confirmation of identity of some peaks on the chromatogram was achieved by collection of the appropriate fractions and examination of the collected material. At least 60 fatty acids were identified, including several not previously reported, such as odd‐numbered carbon chain length monoethenoid acids from C 15 to C 23 .