反相液相色谱中同系物收敛的热力学表征

以液相色谱中的溶质计量置换保留模型(SDM-R)为理论基础,从热力学角度进一步对反相液相色谱中同系物的收敛性进行了研究。建立了溶质平均收敛点坐标的计算方程,并从自由能变的角度表征了收敛点坐标的物理意义,阐明了收敛点的纵坐标相等的原因是溶质在收敛点处的自由能变为零。浓度收敛点的横坐标是1mol纯溶剂的解吸附自由能;而碳数收敛点的横坐标为当流动相中有机溶剂的浓度为纯有机溶剂浓度的十分之一时的同系物端基的保留自由能的负值。并以实验数据对该方程进行了验证,两者符合程度甚佳。

Thermodynamic characterization of convergence coordinates of homologues in reversed-phase liquid chromatography

According to stoichiometric displacement model for retention (SDM - R), the covergent phenomenon of homologues in reversed - phase liquid chromatography (RPLC) was studied. A general equation was derived for calculating the coordinates of the convergent point. The physical meaning of the coordinates was discussed from the point of view of thermodynamics. The ordinates of the two kinds of convergence are the same, i. e. the free energy change of the solutes is equal to zero. The abscissa of the concentration convergence equals to the changes in the desorbed free energy of 1mol pure organic solvent, while that of carbon number convergence equals to the negative free energy change of its end group of the homologue, when the concentration of organic solvent is one tenth in the mobile phase. The derived equation was compared with experimental data and found to fit very well.