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AG + ‐hPLC of conjugated linoleic acids on a silica‐based stationary phase. Part III: Model compounds
Author(s) -
Cross Reginald F.,
Zackari Henrik
Publication year - 2002
Publication title -
journal of separation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.72
H-Index - 102
eISSN - 1615-9314
pISSN - 1615-9306
DOI - 10.1002/1615-9314(20021001)25:14<897::aid-jssc897>3.0.co;2-o
Subject(s) - stearic acid , chemistry , silanol , linoleic acid , conjugated linoleic acid , oleic acid , acetic acid , phase (matter) , organic chemistry , hydrogen bond , double bond , high performance liquid chromatography , chromatography , fatty acid , molecule , biochemistry , catalysis
During the development of a method for the direct analysis of the conjugated linoleic acids (CLAs) in their free fatty acid form, it was necessary to include a competing acid (acetic acid) in the hexane‐based mobile phase in order to achieve resolution of the isomers in a reasonable time. Thus it was clear that the CLAs were retained by two mechanisms. In this study we examine the relative retentions of the CLAs, their methyl esters (CLAMEs, which is the form generally analyzed), and oleic and stearic acids. The primary aim was to investigate the nature of CLA retention in terms of the Ag + ‐π bond interactions (that might be approximated by the retention of the CLAMEs) and the —COOH‐surface silanol hydrogen bonding that should be the same as stearic acid, if the retention mechanisms are independent. Allowing for some retention of the ester group in the CLAMEs on the silica, it may have been expected that the sum of the retention of the CLAMEs and stearic acid would slightly exceed that of the CLAs. On the contrary, it was found that the retention of the CLAs far exceeded the sum for the CLAMEs and stearic acid. Some synergy is suggested, rather than a third retention mechanism.