Study of separation conditions of active components in licorice with two-dimensional liquid chromatography

Licorice, an important natural plant, mainly contains triterpenoids and flavonoids. Glycyrrhizic acid ( glycyrrhizin), 18 beta-glycyrrhetinic acid, liquiritin, isoliquiritigenin, and licochalcone B are typical active components in the two groups. The combination of the RP-RP system was constructed for studying the separation conditions of the above five active components. The different retention characteristics of the five components were exhibited in different two dimensional phase systems. The influences of flow rates, injection concentrations, and temperatures on the separation of these components were studied. The results show that a proper decrease of flow rate is good for gaining high purity of the product. The influences of injection concentration on the separation of active components in a two-dimensional system are not obvious; in the chosen concentration range the nonlinearity of adsorption isotherm for liquiritin is weaker. The study on the influence of temperature and the corresponding thermodynamic analysis show the influence of temperature on the second column is not obvious, but is obvious on the first column; adjusting temperature properly will improve the efficiency of two-dimensional separation and decrease the consumption of organic solvent.