Quantitative analysis of long‐chain trans‐monoenes originating from hydrogenated marine oil

Gas chromatography (GC) is used for the analysis of trans‐fatty acids in partially hydrogenated vegetable oils. Although trans‐isomers of C18 carbon length predominate in partially hydrogenated vegetable oils, trans‐isomers of C20 and C22 carbon length occur in partially hydrogenated fish oil. We re...

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Bibliographic Details
Published in:Lipids 2000-06, Vol.35 (6), p.681-687
Main Authors: Wilson, Robert, Lyall, Karin, Payne, J. Anne, Riemersma, Rudolph A.
Format: Article
Language:English
Subjects:
Adipose Tissue - chemistry
Adult
Chromatography, Gas
Chromatography, Thin Layer
Fatty acids
Fish oils
Fish Oils - chemistry
Humans
Margarine - analysis
Middle Aged
Reference Standards
Reproducibility of Results
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Summary:Gas chromatography (GC) is used for the analysis of trans‐fatty acids in partially hydrogenated vegetable oils. Although trans‐isomers of C18 carbon length predominate in partially hydrogenated vegetable oils, trans‐isomers of C20 and C22 carbon length occur in partially hydrogenated fish oil. We report a simple silver ion chromatographic combined with capillary GC technique for quantitative analysis of trans‐monoenes derived from partially hydrogenated fish oil. Silver nitrate thinlayer chromatographic (TLC) plates are developed in toluene/hexane (50∶50, vol/vol). Fatty acid methyl esters are separated into saturates (Rf 0.79), trans‐monoenes (Rf 0.49), cis‐monoenes (Rf, 0.27), dienes (Rf, 0.10), and polyunsaturated fatty acids with three or more double bonds remaining at the origin. The isolated trans‐monoenes are quantitatively analyzed by capillary GC. The technique of argentation TLC with GC analysis of isolated methyl esters is highly reproducible with 4.8% variation (i.e., coefficient of variation, CV%) in Rf values and 4.3 and 6.9% CV% in quantification within batch and between batch, respectively. Furthermore, the combined technique revealed that direct GC analysis underestimated the trans‐content of margarines by at least 30%. In this study, C20 and C22trans‐monoenes were found in relatively large quantities; 13.9% (range 10.3–19.6%) and 7.5% (range 5.3–11.5%), respectively, in margarine purchased in 1995, but these C20 and C22trans‐monoenes were much reduced (0.1%) in a fresh selection of margarine purchased in 1998. Compositional data from labels underestimated the trans‐content of margarines, especially those dervied from hydrogenated marine oil. Low levels of C20trans‐monoenes (range 0.1–0.3%) and C22trans‐monoenes (range 0.0–0.1%) were identified in adipose tissue obtained from healthy volunteers in 1995, presumably indicating consumption of partially hydrogenated fish oil.
ISSN:0024-4201
1558-9307
DOI:10.1007/s11745-000-0573-3