The modeling of overloaded elution band profiles in supercritical fluid chromatography

Three methods were used to analyze elution bands of methanol on silica, using pure CO2 as the eluent. The results of these analyses were applied to calculate overloaded elution band profiles in supercritical fluid chromatography. The results obtained are compared. To ensure that the mobile phase density varies widely along the column bed, high volumetric flow rates of the mobile phase (CO2) were applied to two columns packed with neat, porous silica. Then, even a slight error made in the determination of the isotherm parameters or during the numerical calculations should be magnified compared to those obtained with a low pressure drop along the column. During the determination of the isotherms of adsorption of methanol from liquid carbon dioxide onto silica, the inlet and outlet pressure of the column, the mass flow rate and the temperature were monitored continuously. Based on these parameters, overloaded elution bands were calculated numerically using three calculation methods. The results are compared with experimental ones.