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High performance liquid chromatography and glass capillary gas chromatography of geometric and positional isomers of long chain monounsaturated fatty acids
Author(s) -
Svensson Lennart,
Sisfontes Leslie,
Nyborg Göran,
Blomstrand Rolf
Publication year - 1982
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02535122
Subject(s) - chemistry , chromatography , structural isomer , high performance liquid chromatography , cis–trans isomerism , fatty acid , gas chromatography , organic chemistry
Positional and geometrical isomers of monounsaturated long chain fatty acids were analyzed by the combination of high performance liquid chromatography (HPLC) and glass capillary gas chromatography (GC). A preparative group separation of cis and trans isomers of the monounsaturated fatty acid methyl esters was achieved according to chain length by reversed‐phase HPLC, and using a highly sensitive interference refractive index detector. After collection of the different fractions containing cis and trans forms of the monounsaturated fatty acid methyl esters, the fractions were analyzed for their content of positional isomers using glass capillary GC with Silar‐5 CP as stationary phase. The preparative step in the HPLC was also used analytically for the determination of the ratio between the cis and trans monounsaturated fatty acids. A comparison was made between the results obtained with the HPLC technique and the results of a GLC technique with a packed OV‐275 column. There was a good correlation between the 2 techniques with a tendency to higher trans values with the HPLC technique (4%). It was shown with reference substances that 18∶1ω6‐ cis to ω11‐ cis and 18∶1ω5‐ trans to ω12‐ trans , the most common monounsaturated fatty acid isomers in partially hydrogenated vegetable oils, could be almost quantitatively recovered in the HPLC step. Most of the individual positional isomers of monounsaturated fatty acids of varying chain length could be separated and determined in the glass capillary GC step with the exception of those isomers containing the double bond in a relatively high ω‐position. The relative standard deviation of the technique as determined with reference substances was better than 4%. The described technique was applied to the analysis of the isomeric monounsaturated fatty acid content in partially hydrogenated vegetable and marine oils, and about 5 samples a day could be executed.