二苯甲醇类结构异构体的胶束纸色谱法分离及其色谱行为

Micellar Paper Chromatographic Separation of Structural Isomers of Diphenylmethyl Alcohols and Their Chromatographic Behaviour

应用胶束纸色谱法使９种二苯甲醇的结构异构体得到了分离，Ｃｍ对Ｒｆ／（１－Ｒｆ）的曲线不仅偏离了Ａｒｍｓｔｒｏｎｇ理想曲线，而且呈锯齿状，其原因在于二苯甲醇类化合物具有大的立体效应。溶质的分子结构与胶束空穴的形状、大小适配，是色谱分离的主要驱动力。

Structural isomers of nine diphenylmethyl alcohols (DPMA) have been separated by paper chromatography with sodium dodecylsulfate(SDS) micellar pure water solution as mobile phase and their R f  data are measured in different concentrations of SDS surfactant aqueous solution with no other additives. However, the curves of C m  vs R f /(1-R f)  deviate considerably from the Armstrong′s ideal curve and are sawtoothed. The reason is that there is a big stereoscopic effect of DPMA compounds. The partly antibinding behaviour of the sawtoothed shapes comes from the effect which decides that DPMA cannot enter micellar core, otherwise the entropy of micellar system would be reduced or micellar will be broken, although both of them have hydrophobic property. One of the Armstrong′s equations is shown as:R f 1-R f =1Kθ+K m C m KθIn this case, K m  in the equation is negative. The above equation comes from a special condition in which there is only one type of micelle, however, there are several kinds of micelles for real system which is in dynamic equilibrium. Armstrong gave the correct pseudophase retention equation for 2∶1 complexesR f 1-R f =1Kθ+K 1C m Kθ+K 1K 2C m 2KθThe DPMAs′ chromatographic behaviour is the synthetic results of K 1 and K 2, both of which can be more than or less than zero, respectively or simultaneously, so the curves show sawtoothed shapes. The suitability of the relationship between the solutes′ molecular structures and the micellar shapes and sizes is the main driving force of chromatographic separation.