Improved separation of conjugated fatty acid methyl esters by silver ion-high-performance liquid chromatography

Operating from one to six silver ion‐high‐performance liquid chromatography (Ag+‐HPLC) columns in series progressively improved the resolution of the methyl esters of conjugated linoleic acid (CLA) isomeric mixtures from natural and commercial products. In natural products, the 8 trans, 10 cis‐octad...

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Bibliographic Details
Published in:	Lipids Vol. 34; no. 4; pp. 407 - 413
Main Authors:	Sehat, N, Rickert, R, Mossoba, M.M, Kramer, J.K.G, Yurawecz, M.P, Roach, J.A.G, Adlof, R.O, Morehouse, K.M, Fritsche, J, Eulitz, K.D
Format:	Journal Article
Language:	English
Published:	Berlin/Heidelberg Springer‐Verlag 01-04-1999 Springer Nature B.V
Subjects:	8 trans. 10 cis-octadecadienoic (18:2) acid Chromatography Chromatography, High Pressure Liquid - methods Esters Esters - chemistry fatty acid esters Fatty acids Fatty Acids - chemistry Fatty Acids - isolation & purification food analysis Fourier transform infrared spectroscopy Fourier transforms Gas chromatography high performance liquid chromatography Infrared spectroscopy Ionization Isomerism isomers linoleic acid Liquid chromatography Mass spectrometry separation Silver
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Summary:	Operating from one to six silver ion‐high‐performance liquid chromatography (Ag+‐HPLC) columns in series progressively improved the resolution of the methyl esters of conjugated linoleic acid (CLA) isomeric mixtures from natural and commercial products. In natural products, the 8 trans, 10 cis‐octadecadienoic (18∶2) acid was resolved from the more abundant 7 trans, 9 cis‐18∶2, and the 10 trans, 12 cis‐18∶2 was separated from the major 9 cis, 11 trans‐18∶2 peak. In addition, both 11 trans, 13 cis‐18∶2 and 11 cis, 13 trans‐18∶2 isomers were found in natural products and were separated; the presence of the latter, 11 cis, 13 trans‐18∶2, was established in commercial CLA preparations. Three Ag+‐HPLC columns in series appeared to be the best compromise to obtain satisfactory resolution of most CLA isomers found in natural products. A single Ag+‐HPLC column in series with one of several normal‐phase columns did not improve the resolution of CLA isomers as compared to that of the former alone. The 20∶2 conjugated fatty acid isomers 11 cis, 13 trans‐20∶2 and 12 trans, 14 cis‐20∶2, which were synthesized by alkali isomerization from 11 cis, 14 cis‐20∶2, eluted in the same region of the Ag+‐HPLC chromatogram just before the corresponding geometric CLA isomers. Therefore, CLA isomers will require isolation based on chain length prior to Ag+‐HPLC separation. The positions of conjugated double bonds in 20∶2 and 18∶2 isomers were established by gas chromatography‐electron ionization mass spectrometry as their 4,4‐dimethyloxazoline derivatives. The double‐bond geometry was determined by gas chromatography‐direct deposition‐Fourier transform infrared spectroscopy and by the Ag+‐HPLC relative elution order.
Bibliography:	http://hdl.handle.net/10113/25467 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0024-4201 1558-9307
DOI:	10.1007/s11745-999-0379-3