A Study of Chromatographic Resolution of Enantiomers: Solvent Characteristics of Supercritical Fluid and Liquefied Gas

本文研究了超临界二氧化碳和液化丙烷作为流动相在色谱拆分有机活性异构体中的分离特性。用手性纤维素衍生物包覆在硅胶上的色谱柱拆分了两个对映体--反式二苯乙烯氧化物和1-(9-蒽基)-2，2，2-三氟乙醇。实验结果如下：(1)二氧化碳、丙烷、己烷的拆分顺序较高，且与各溶剂中的扩散系数平行。(2)三种溶剂的容量比随醇浓度的增加而减小。在超临界流体情况下，它也随着压力的增加而减小。这些现象可能是由于溶质和溶剂分子在活性中心上的竞争吸附所致。(3)分离因子随温度的降低而显著增大，并且随主要流体和添加…的组合而变化不大更多的酒精。吸附对映体的相对稳定性主要受吸附相中溶质-聚合物相互作用的影响，其次受吸附相中溶质-溶剂相互作用的影响。(4)随着超临界流体压力的增加，对映体的分离因子略有增加，与吸附相中乙醇浓度的降低相对应。(5)在以分子扩散和流体混合为主的低速区域，聚合物涂层硅胶的总传质阻力小于裸胶，而在高速区域，聚合物涂层硅胶表现出比裸胶更高的阻力。可能有两种合理的解释：1)由于聚合物的夹杂而增加了多孔颗粒中的弯曲因子；2)由于聚合物附着在颗粒的外部而导致颗粒的聚集。为了提高柱效，有必要对聚合物包覆方法进行基础性研究。较少

The present work concerns with the separation characteristics of the supercritical carbon dioxide and liquified propane as a mobile phase in chromatographic resolution of potically active isomers. Two enantiomers, trans-stilbene oxide and 1-(9-anthryl)-2,2,2-trifluoroethanol, were resolved by a column with a chiralcellulose derivative coated on a silica gel. The experimental results are summarized as follows.(1) Carbon dioxide, propane and hexane are in the order of high resolution; the order is in parallel to the diffusivity in each solvent.(2) The capacity ratio decreases with increasing the concentration of alcohols for the three solvents. It also decreases with increasing pressure in case of the supercritical fluid. These observations may be explained by the competitive adsorptions of solute and solvent molecules on active sites.(3) The separation factor significantly increases with decreasing temperature, and it changes a little according to the combination of major fluids and add … More ed alcohols. The relative stability of adsorbed enantiomers may be controlled majorly by the solutes-polymer interactions and secondly by the solutes-solvents interactions in the adsorbed phase.(4) The separation factor of enantiomers increases slightly with increasing pressure of the supercritical fluid, which corresponds to the decrease of alcohol concentration in the adsorbed phase.(5) In a low velocity region where molecular diffusion and fluid-mixing are predominant, the overall mass transfer resistance for polymer-coated silica gel is smaller than that for the naked gel; however, in a high velocity region, the polymer-coated silica gel shows higher resistance than the naked. There may be two plausible explanations: 1) increase of the tortuosity factor in the porous particle due to the inclusion of polymers 2) particle coalescence due to the polymers attached on the outside of particles. The fundamental research on polymer coating method will be necessary for improving column efficiency. Less