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The relative FID responses for Iatroscan analyses ofcis andtrans isomers of methyl esters of 18∶1†6, 18∶1†9 and 18∶1†11 on Chromarods-S impregnated with AgNO3 were studied at load levels ranging from 0.5 to 20 μg, using methyl stearate as internal standard. The FID response correction
factors were greater for thecis than for thetrans isomers. The correction factors were relatively constant in the 10–20 μg interval, but increased in the range 0.5–5 μg.
Separation of tristearin, triolein, trilinolein and trilinolenin also was obtained on Chromarods-S impregnated with AgNO3 using a mixture of benzene: chloroform: acetic acid (90∶8∶2) as the solvent system. The relative FID responses for the triolein,
trilinolein and trilinolenin were determined at load levels ranging from 0.5 to 14.3 μg using tristearin as an internal standard.
The FID response correction factors of these three triglycerides differed significantly for load levels of 1.0, 2.5 and 5.0
μg. However, the factors could be considered as being equal in the range 10 to 14.3 μg.
Correction factors were not affected by repeated re-use of the same set of Chromarods. Several hundred separations and scans
appeared feasible. 相似文献
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Susanne Bech Pedersen Gunhild Hølmer 《Journal of the American Oil Chemists' Society》1995,72(2):239-243
The fatty acid specificity of the lipase fromRhizomucor miehei toward 20:1n-9, 20:5n-3, 22:1n-9 and 22:6n-3 has been determined by comparing the alcoholysis (byn-propanol) of various mixtures of C20 and C22 fatty acids (FFA) or the corresponding ethyl esters (FAEE) inn-heptane. For all the fatty acids examined, the degree of conversion was much higher when using FFA rather than FAEE. When
comparing the experiments with either single FAEE or FAEE mixtures, it was found for all four fatty acids that the degree
of conversion depended on whether the FAEE was alone or together with other fatty acids in the reaction mixture. The lipase
showed a strong specificity toward 20:1n-9, whereas the polyunsaturated fatty acids were much poorer substrates, especially
22:6n-3. The degrees of conversion for the two n-3 fatty acids show a clear preference for 20:5n-3 over 22:6n-3, not only
when present alone but also in the different mixtures examined. The results obtained in the present experiments therefore
suggest that when using the lipase fromR. miehei for enrichment of fish oils with n-3 fatty acids, it should not only be possible to diminish the content of 20:1 and 22:1
present in the outer positions in the triacylglycerols, but also to incorporate relatively more 20:5n-3 than 22:6n-3 into
the triglycerides. 相似文献
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Antti Aro Truus Kosmeijer-Schuil Peter van de Bovenkamp Paul Hulshof Peter Zock Martijn B. Katan 《Journal of the American Oil Chemists' Society》1998,75(8):977-985
Trans fatty acids in foods are usually analyzed by gas-liquid chromatography (GLC) of fatty acid methyl esters (FAME). However,
this method may produce erroneously low values because of insufficient separation between cis and trans isomers. Separation can be optimized by preceding silver-ion thin-layer chromatography (Ag-TLC), but this is laborious. We
have developed an efficient method for the separation of 18-carbon trans fatty acid isomers by combining GLC of FAME with GLC of fatty acid 4,4-dimethyloxazoline (DMOX) derivatives. We validated
this method against conventional GLC of FAME, with and without preceding Ag-TLC. Fatty acid isomers were identified by comparison
with standards, based on retention times and mass spectrometry. Analysis of DMOX derivatives allowed the 13t, 14t, and 15t isomers to be separated from the cis isomers. The combination of the GLC analyses of FAME and DMOX derivatives gave results comparable with those obtained by
GLC of FAME after preceding Ag-TLC, while saving about 100 h of manpower per 25 samples. It allowed the identification and
quantitation of 11 trans and 8 cis isomers and resulted in 25% higher values for total C18:1
trans, compared with the analysis of FAME alone. The combination of DMOX and FAME analyses, as applied to the analysis of 14 foods
that contained ruminant fat and partially hydrogenated vegetable and fish oils, indicated that the most common isomers were
11t in ruminant fats, 9t in partially hydrogenated fish fats, and either 9t or 10t in partially hydrogenated vegetable fats. The combination of GLC analyses of FAME and DMOX derivatives of fatty acids improves
the quantitation of 18-carbon fatty acid isomers and may replace the laborious and time-consuming Ag-TLC. 相似文献
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The influence of additives such as calcium sulfate hemi-hydrate, sodium sulfate, sodium carbonate, calcium carbonate, citric acid and surface active agent upon the hydration at 20°C of the mixture of C11A7.CaF2, C3S and CaSO4 was investigated. Some discussions were made on the behaviors of additives which affected the properties of the hardened paste. 相似文献