SEPARATION OF VITAMIN-E AND GAMMA-ORYZANOLS FROM RICE BRAN BY NORMAL-PHASE CHROMATOGRAPHY

Five commercial silicas [Nova Pak, mu Porasil (Waters, Milford, MA), Kromasil (Eka Nobel, Bohus, Sweden) Spherisorb (Sigma, St. Louis, MO) and Select-KP (Biotage, Charlottesville, VA)] were tested for their efficiency in separating vitamin E and gamma-oryzanol components from saponified rice bran extracts, with the perspective of future large-scale purification of the various compounds. The effects of mobile phase composition, eluent flow rate, column temperature and the physical properties of the silica on the selectivity and analysis time were studied. All silicas except Select-KP gave baseline separation of the vitamin E components with isooctane/ethyl acetate (97.5:2.5) at room temperature. However, only the 4-mu m Nova Pak spherical silica gave adequate resolution of the oryzanols into two distinct fractions with an analysis time of circa 20 min. Other analytical conditions, i.e., the content of the polar modifier in the mobile phase, temperature and flow rate, can be used to optimize the separation once the silica had been chosen. Speed of separation is enhanced by increasing the polarity of the eluent, temperature and flow rate, while the selectivity is reduced only slightly The Nova-Pak silica appears resistant to deactivation from both residual water in the mobile phase and polar components left over after sample clean up and is suitable for preparative separation of the target compounds.