胆酸在5种溶剂中的溶解度测定及关联

Measurement and correlation of cholic acid solubility in five solvents

采用重量法测定了胆酸在甲醇、乙醇、乙酸乙酯、冰醋酸和正丙醇中的溶解度数据,并采用ModifiedApelblat模型、λh模型、二次多项式模型和三参数van't Hoff模型对溶解度数据进行了拟合。通过修正的van't Hoff方程分析溶解过程的热力学参数(吉布斯自由能变ΔmixG、焓变ΔmixH和熵变ΔmixS),并计算了焓相对贡献ζH和熵相对贡献ζTS。结果表明,二次多项式模型对溶解度的关联效果最好。在研究所采用的溶剂体系中,ΔmixH>0,ΔmixS>0,ΔmixG>0,说明胆酸的溶解是非自发、不可逆的吸热过程。焓的相对贡献ζH远大于熵的相对贡献ζTS,说明胆酸在所选的溶剂的溶解过程中,溶解焓变ΔsolH对溶解吉布斯能变ΔsolG的贡献大于溶解熵变ΔsolS。这些溶解度和热力学性质可为胆酸结晶工艺提供重要的依据。

The solubility data of cholic acid in methanol,ethanol,ethyl acetate,acetic acid and n-propanol were measured by weighting and fitted by the Modified Apelblat model,λh model,quadratic polynomial model and three-parameters van't Hoff model.The thermodynamic parameters of the dissolution process(Gibbs free energy variationΔmixG,enthalpy variationΔmixH,and entropy variationΔmixS)were analyzed by modified van't Hoff equation,and the relative contribution of enthalpyζH and entropy contributionζTS were also calculated.The results show that the quadratic polynomial model has the best correlation effect for solubility.The results ofΔmixH>0,ΔmixS>0 andΔmixG>0 for solvents studied indicate that the dissolution of cholic acid is a non-spontaneous and irreversible endothermic process.The relative contribution of enthalpyζH was larger than that of entropyζTS,which indicates that the dissolved enthalpy variableΔsolH contributes more to the dissolved Gibbs energy variableΔsolG than that of the dissolved entropy variableΔsolS.The obtained solubility and thermodynamic properties can provide basic data for crystallization studies of cholic acid.