反相液相色谱中同系物保留过程中的等焓点  

Iso-enthalpy Point of Homologues in High Performance Reversed Phase Liquid Chromatography

作　　者：张维平[1] 郭鸿[1] 耿信笃[1] 

机构地区：[1]西北大学现代分离科学研究所,西安710069

出　　处：《分析化学》2000年第4期480-485,共6页Chinese Journal of Analytical Chemistry

基　　金：国家自然科学基金!29675017

摘　　要：依据液相色谱中溶质计量置换保留模型，从理论上分别推导出了在反相高效液相色谱（RPLC）中同系物端基和重复结构单元对Z（1mol）溶剂化溶质被固定相吸附时，在其接触表面释放出溶剂的摩尔总数）与绝对温度倒数间的线性关系式。也从分子结构参数推导出了同系物端基对总焓变的贡献△Hi和同系物非端基（或链长）对总焓变的贡献△HsNc的表达式。从而建立了等焓点的坐标方程，阐明了等焓点的纵坐标相等是溶质在等焓点处的焓变为零，等焓点的横坐标是当流动相中有机溶剂的浓度为10％时同系物端基的保留焓变。它们的物理意义为在此点溶质的焓变相等。其各溶质自由能变的差别完全取决于熵变，并以实验数据对该坐标方程进行了验证，两者符合较好。还用分值△Hi和△HsNe对总焓变面△H进行了估算，其估算值与实验值符合程度尚可，其相对偏差小于±8％。Based on stoichiometric displacement model for retention(SDM-R) in liquid chromatography,two linear relations for the plots of i (the total contributions of the end and branched groups of one molehomologue to the total Z value of the homologue) and s (the contribution of one mole of repeatedstiuctural unit of the hamologue to the Z value of the homologue) in reversed-phase high performanceliquid chromatogrpahy (RPLC) were theoretically derived, respectively. The total enthalpy change of thehomologue can he divided into two parts, the total contributions of one mole of the end and branchedgroups △Hi and one mole of total numbers of the repeaed strctural units of the homologue △HsNerespectively. A genetal equation was derived to calculate the coordinates of the iso-enthalpy point. Theordinate of the iso-enthalpy equals to zero. Its corresponding abscissca equals to the nagative enthalpychange of its end and branched groups of the homologue, as the concentration of organic solvent is oftenth of the emplyoyed pure sovent in the mobile phase. The physical meaning of the iso-enthalpy pointis of the same for various member of the homologue. In this circumstance, the different free energychange of each member only depends on their enthpy changes. The derived equations were tested withexperimental data and found to fit very well. The △Hi and the △HsNc were used to evaluate △H. Withthe comparison s between the experimental and evaluated results, the standard deviation was found to beless than ±8%.

关 键 词：反相液相色谱 等焓点 同系物 计量置换保留模型 

分 类 号：O657.7[理学—分析化学]