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Effect of pressure on the selectivity of polymeric C18 and C30 stationary phases in reversed-phase liquid chromatography. Increased separation of isomeric fatty acid methyl esters, triacylglycerols, and tocopherols at high pressure

Okusa, Kensuke; Iwasaki, Yuki; Kuroda, Ikuma; Miwa, Shohei; Ohira, Masayoshi; Nagai, Toshiharu; Mizobe, Hoyo; Gotoh, Naohiro; Ikegami, Tohru; McCalley, David V.; Tanaka, Nobuo

Authors

Kensuke Okusa

Yuki Iwasaki

Ikuma Kuroda

Shohei Miwa

Masayoshi Ohira

Toshiharu Nagai

Hoyo Mizobe

Naohiro Gotoh

Tohru Ikegami

Nobuo Tanaka



Abstract

A high-density, polymeric C18 stationary phase (Inertsil ODS-P) or a polymeric C30 phase (Inertsil C30) provided improved resolution of the isomeric fatty acids (FAs), FA methyl esters (FAMEs), triacylglycerols (TAGs), and tocopherols with an increase in pressure of 20-70. MPa in reversed-phase HPLC. With respect to isomeric C18 FAMEs with one cis-double bond, ODS-P phase was effective for recognizing the position of a double bond among petroselinic (methyl 6Z-octadecenoate), oleic (methyl 9Z-octadecenoate), and cis-vaccenic (methyl 11Z-octadecenoate), especially at high pressure, but the differentiation between oleic and cis-vaccenic was not achieved by C30 phase regardless of the pressure. A monomeric C18 phase (InertSustain C18) was not effective for recognizing the position of the double bond in monounsaturated FAME, while the separation of cis- and trans-isomers was achieved by any of the stationary phases. The ODS-P and C30 phases provided increased separation for TAGs and β- and γ-tocopherols at high pressure. The transfer of FA, FAME, or TAG molecules from the mobile phase to the ODS-P stationary phase was accompanied by large volume reduction (-30. ~. -90. mL/mol) resulting in a large increase in retention (up to 100% for an increase of 50. MPa) and improved isomer separation at high pressure. For some isomer pairs, the ODS-P and C30 provided the opposite elution order, and in each case higher pressure improved the separation. The two stationary phases showed selectivity for the isomers having rigid structures, but only the ODS-P was effective for differentiating the position of a double bond in monounsaturated FAMEs. The results indicate that the improved isomer separation was provided by the increased dispersion interactions between the solute and the binding site of the stationary phase at high pressure. © 2014 Elsevier B.V.

Journal Article Type Article
Publication Date Apr 25, 2014
Journal Journal of Chromatography A
Print ISSN 0021-9673
Electronic ISSN 1873-3778
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 1339
Pages 86-95
APA6 Citation Okusa, K., Iwasaki, Y., Kuroda, I., Miwa, S., Ohira, M., Nagai, T., …Tanaka, N. (2014). Effect of pressure on the selectivity of polymeric C18 and C30 stationary phases in reversed-phase liquid chromatography. Increased separation of isomeric fatty acid methyl esters, triacylglycerols, and tocopherols at high pressure. Journal of Chromatography A, 1339, 86-95. https://doi.org/10.1016/j.chroma.2014.02.077
DOI https://doi.org/10.1016/j.chroma.2014.02.077
Keywords fatty acid methyl esters, triacylglycerols, tocopherols, high performance liquid chromatography, isomers
Publisher URL http://dx.doi.org/10.1016/j.chroma.2014.02.077
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