Behavior of tocopherol homologues in silica-gel liquid chromatography

A general rate model, in which axial dispersion, liquid film mass transfer and effective diffusion in particles were taken into consideration, was adopted to investigate the chromatography process for tocopherols. The finite element and orthogonal collocation method were used to transform these equations to ordinary differential equations and to solve them. The simulation results agreed well with the experimental data. The relationship between the film mass-transfer coefficient and the interstitial velocity and the effective diffusion coefficient were measured. The scale-up of separation of the tocopherols from analytical to preparative scale was achieved. Total tocopherols were separated with n-hexane-isopropanol as the mobile phase using a silica-gel column. Effects of composition and the flow rate of the mobile phase on separation were investigated. As the concentration of isopropanol in the mobile phase increases, the capacity factor and the resolution decrease. The best concentration of isopropanol in the mobile phase is 1%.