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Analysis of alpha‐linolenic acid geometrical isomers in deodorized oils by capillary gas‐liquid chromatography on cyanoalkyl polysiloxane stationary phases: A note of caution
Author(s) -
Wolff Robert L.
Publication year - 1994
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02540472
Subject(s) - isomerization , chemistry , chromatography , elution , fatty acid , gas chromatography , cis–trans isomerism , capillary action , linolenic acid , organic chemistry , linoleic acid , catalysis , materials science , composite material
Analysis of alpha‐linolenic acid geometrical isomers in deodorized or heated oils by capillary gas‐liquid chromatography (GLC) on polar cyanoalkyl polysiloxane stationary phases requires some care to avoid interferences with other fatty acids. Depending on the temperature of the column, the cis ‐11 20∶1 acid may elute before, with or after the cis ‐9, cis ‐12, cis ‐15 18∶3 acid during GLC. In some instances [temperature higher than 180°C with a CP Sil 88 column (Chrompack, Middelburg, The Netherlands)], the 20∶1 acid coelutes with the trans ‐9, cis ‐12, cis ‐15 18∶3 acid, leading to abnormally high levels of this last isomer. Consequently, the degree of isomerization of alpha‐linolenic acid will be over‐estimated under such conditions. It is recommended that the behavior of cis ‐11 20∶1 acid relative to temperature be checked carefully prior to the determination of alpha‐linolenic acid geometrical isomers by GLC. Temperatures lower than 160°C seem appropriate to separate all of these components from each other and from cis ‐11 20∶1 acid in a 50 m×0.25 mm i.d. CP Sil 88 capillary column.