Study of relationship among solution concentration-boiling point-saturation vapor pressure for glycyrrhizic acid solution / 中草药

ABSTRACT

Objective Based on the theory of dynamic method for measuring the boiling point-saturated vapor pressure, the functional relationship between the boiling point and saturation vapor pressure was studied for the glycyrrhizic acid solution. To build the relationship among the mass fraction of glycyrrhizic acid solution, boiling point and saturation vapor pressure, in order to provide the experimental data and theoretical basis for the related studies of traditional Chinese medicine concentration process. Methods The concentration of glycyrrhizic acid was determined by UPLC for different concentration of glycyrrhizic acid solution. Also, the surface tension of glycyrrhizic acid solution was measured by platinum plate method. Based on dynamic method, the boiling point was measured with the changing saturated vapor pressure at the different mass fractions of solution. Results The concentration of glycyrrhizin in the original extract was 99.25 mg/mL, which accounted for 21.5% of the total solid soluble substance. The dilution process is fully even and conforms to the gradient ratio. When the solution mass fraction was more than 18%, the micelle was formed gradually in the liquid, reducing the surface tension of the solution. It can be found that the boiling point showed the downward trend with increasing solution concentration of glycyrrhizic acid, while the pressure was maintained constant in the environment. When the temperature of solution was hold constant, the saturation vapor pressure of the solution increased with increasing solution concentration of glycyrrhizic acid, but the trend of this interaction was not obvious between the temperature range (313.0—343.0 K). Conclusion According to the experimental results, the functional relationship among the concentration, boiling point and saturated vapor pressure of glycyrrhizic acid solution was constructed. While maintaining the concentration vacuum and the heating energy consumption unchanged in the production process, the glycyrrhizic acid solution temperature should slowly decrease and the evaporation rate should be moderately accelerated with the increasing mass fraction of solution.