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Use of a polar‐embedded stationary phase for the separation of tocopherols by CEC
Author(s) -
CarabiasMartínez Rita,
RodríguezGonzalo Encarnacion,
Smith Norman W.,
RuanoMiguel Luis
Publication year - 2006
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.200600223
Subject(s) - polar , chemistry , phase (matter) , alkyl , selectivity , elution , structural isomer , amide , resolution (logic) , chromatography , methanol , hydrophilic interaction chromatography , analytical chemistry (journal) , organic chemistry , high performance liquid chromatography , physics , astronomy , artificial intelligence , computer science , catalysis
A polar‐embedded stationary phase (ULTIMA C18) has been investigated for the separation of α‐, β‐, γ‐ and δ‐tocopherols by CEC in comparison with commercially available C 18 and C 30 n ‐alkyl RPs. The behavior of this stationary phase was tested for different mobile phases based on methanol, ACN, or mixtures thereof and different separation parameters such as retention factors and resolution were evaluated. The main feature of this stationary phase is the improved selectivity for the separation of β‐ and γ‐tocopherols (positional isomers) when compared with the pure n ‐alkyl C 18 material, which was unable to resolve these compounds. Additionally, it is possible to observe a reversal in the elution order of the β‐ and γ‐tocopherol isomers with respect to that obtained on the C 30 column. The resulting data indicate that the enhanced selectivity obtained with the polar‐embedded stationary phase, with respect to the conventional C 18 material, is due to the participation of both hydrophobic and polar interactions: these latter are of the hydrogen bridge type with the amide group of the polar‐embedded stationary phase, which increases the retention of the tocopherols and facilitates the discrimination between the β‐ and γ‐isomers. Adequate separation of the four tocopherols was obtained by CEC using the polar‐embedded stationary phase and 95:5 v/v methanol/water (5 mM Tris, final concentration) as the mobile phase.