title: 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.
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 20-70MPa 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∼-90mL/mol) resulting in a large increase in retention (up to 100% for an increase of 50MPa) 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.
authors.affiliation: GL Sciences Inc., Iruma, Saitama 358-0032, Japan.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Okusa
authors.affiliation: GL Sciences Inc., Iruma, Saitama 358-0032, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Iwasaki
authors.affiliation: GL Sciences Inc., Iruma, Saitama 358-0032, Japan.
authors.forename: Ikuma
authors.initials: I
authors.lastname: Kuroda
authors.affiliation: GL Sciences Inc., Fukushima, 960-8201, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Miwa
authors.affiliation: GL Sciences Inc., Iruma, Saitama 358-0032, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Ohira
authors.affiliation: Tsukishima Foods Industry Co., Edogawa-ku, Tokyo 134-8520, Japan.
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Nagai
authors.affiliation: Tsukishima Foods Industry Co., Edogawa-ku, Tokyo 134-8520, Japan.
authors.forename: Hoyo
authors.initials: H
authors.lastname: Mizobe
authors.affiliation: Tokyo University of Marine Science and Technology, Minato-ku, Tokyo, 108-8477, Japan.
authors.forename: Naohiro
authors.initials: N
authors.lastname: Gotoh
authors.affiliation: Kyoto Institute of Technology, Kyoto 606-8585, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Ikegami
authors.affiliation: University of the West of England, Bristol BS16 1QY, UK.
authors.forename: David V
authors.initials: DV
authors.lastname: McCalley
authors.affiliation: GL Sciences Inc., Iruma, Saitama 358-0032, Japan. Electronic address: n-tanaka@gls.co.jp.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Tanaka
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods; D056148:Chromatography, Reverse-Phase / Q000295:instrumentation / Q000379:methods; D004952:Esters; D004958:Estradiol / Q000737:chemistry; D005227:Fatty Acids / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D007536:Isomerism; D011312:Pressure; D013696:Temperature; D024505:Tocopherols / Q000737:chemistry*; D014280:Triglycerides / Q000737:chemistry*
chemical_list: D004952:Esters; D005227:Fatty Acids; D014280:Triglycerides; D004958:Estradiol; D024505:Tocopherols
keywords: C30; Fatty acid methyl esters; High pressure; Polymeric ODS; Tocopherols; Triacylglycerols