Fatty acids of cows' milk. A. Techniques employed in supplementing gas-liquid chromatography for identification of fatty acids |
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Authors: | Paul Magidman S F Herb R A Barford R W Riemenschneider |
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Affiliation: | (1) Eastern Regional Research Laboratory, Philadelphia 18, Pennsylvania |
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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 ascis-trans, trans-trans or both. Isolatedtrans 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 C15 to C23.
Presented at the 53rd Meeting of the American Oil Chemists' Society, October 17–19, 1960, New York.
Eastern Utilization Research and Development Division, Agricultural Research Service, United States Department of Agriculture. |
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