Study on retention factor and resolution of tocopherols by supercritical fluid chromatography

To develop a process for separation of natural α-tocopherol from γ- and δ-tocopherols by supercritical fluid chromatography, the effects of pressure, temperature and the ethanol concentration in the mobile phase on the retention factor and resolution of tocopherols were studied comprehensively. The ranges of the studied pressure, temperature and ethanol concentration were 12 to 20 MPa, 30 to 90 °C and 0 to 6.54 wt% respectively. It was found that the retention factors of the tocopherols decrease as the ethanol concentration in the mobile phase increases. The resolution of tocopherols increases as the temperature increases and as the pressure decreases, and there is a maximum of the ethanol concentration curve at a definite temperature and pressure. A simplified model of the retention factor ln k′=A+BT+Cρ−D(ρT)+E(ρ2T) based on the unified molecular theory was proposed. The experimental data were correlated by the model with the AARD% less than 14.70%.