Submitted to: International Symposium on High Performance Liquid Phase Separations
Publication Type: Abstract Only
Publication Acceptance Date: 8/8/1998
Publication Date: N/A
Technical Abstract: Tocotrienols occur in plants as a complex mixture of 2-methyl-6-chromanol homologues and aromatic ring position isomers. Accurate quantification of the tocotrienol components provides information on antioxidant levels in lipids. We report the first separation of tocotrienols by silver-ion high-performance liquid chromatography with fluorescence detection. Alpha-, beta-, gamma-, and delta-tocotrienols were analyzed with a silver-ion treated spherical silica column. Mobile phases employed variable proportions of hexane- isopropanol-ethyl acetate. Separations of geometrical isomers and and homologous tocotrienols were readily achieved under optimized conditions. However, it was difficult to separate position isomers, beta-, and gamma- tocotrienols, and their acetate derivatives. Presence of an ester or an ether in hexane- isopropanol mobile phases favored separation of position isomers. Because of the intrinsic difference in polarity and hydrophobicity of geometrical isomers, analyte peaks were found to interpose with one another among early-, and later-eluting homologous peaks. The elution order beta->gamma- >delta- >alpha- tocotrienols observed in silver ion HPLC was not the same as found in reversed-phase or normal-phase HPLC. Silver-ion HPLC technique facilitates structural analyses of the sixteen tocotrienol components by HPLC-NMR and HPLC-MS.