Liapis Athanasios I, Grimes Brian A
Department of Chemical and Biological Engineering and Biochemical Processing Institute, University of Missouri-Rolla, Rolla, Missouri 65409-1230, USA.
J Sep Sci. 2007 Mar;30(5):648-57. doi: 10.1002/jssc.200600421.
Most often, in bioseparations involving charged macromolecules, the chromatographic systems have low Reynolds and high Peclet numbers. For such systems, an expression is developed and presented in this work for evaluating the throughput in polymeric monoliths where ion-exchange adsorption occurs, as a function of (i) the pressure drop along the length of the monolith, (ii) the functional form and width of the throughpore-size distribution of the monolith, and (iii) the magnitude of the zeta potential on the surface of the throughpores of the monolith. Gaussian and log-normal throughpore-size distributions whose mean throughpore-size and standard deviation values are based on experimentally measured throughpore-size distribution data by mercury porosimetry employed on polymeric monoliths are used in this work, and their effect on the throughput relative to that obtained from a polymeric monolith having a uniform throughpore-size distribution is studied for different values of the ratio of the standard deviation to the mean throughpore-size. The results indicate that relatively modest increases in the throughput, when compared with the throughput that could be achieved in a polymeric monolith having a uniform throughpore-size distribution, could be obtained in polymeric monoliths having disperse throughpore-size distributions, and the magnitude of the increase becomes larger when the disperse distribution is skewed to larger throughpore sizes. Furthermore, the results of this work indicate that, under certain conditions, relatively modest increases in the throughput of a charged analyte could also be achieved by altering the value of the zeta potential on the surface of the throughpores of the monolith. Due to the difficulties inherent in controlling the functional form and width of the throughpore-size distribution during the synthesis of polymeric monoliths, it would appear to be more practical to increase the value of the throughput of a charged analyte by altering the value of the zeta potential through prudent selection of the ion-exchange surface functional groups and fine-tuned with the pH of the mobile phase. Thus, for ion-exchange chromatography systems, the zeta potential could be considered an important parameter for column designers and operators to manipulate, since its alteration could increase the through-put of a charged analyte in polymeric monoliths or in columns packed with charged particles.
在涉及带电大分子的生物分离过程中，色谱系统的雷诺数通常较低，而佩克莱数较高。对于此类系统，本文推导并给出了一个表达式，用于评估发生离子交换吸附的聚合物整体柱中的通量，该通量是以下因素的函数：(i) 沿整体柱长度方向的压降；(ii) 整体柱通孔尺寸分布的函数形式和宽度；(iii) 整体柱通孔表面zeta电位的大小。本文使用了高斯和对数正态通孔尺寸分布，其平均通孔尺寸和标准偏差值基于通过聚合物整体柱压汞法实验测量得到的通孔尺寸分布数据，并针对标准偏差与平均通孔尺寸之比的不同值，研究了它们相对于具有均匀通孔尺寸分布的聚合物整体柱所获得的通量对通量的影响。结果表明，与具有均匀通孔尺寸分布的聚合物整体柱相比，具有分散通孔尺寸分布的聚合物整体柱的通量会有相对适度的增加，并且当分散分布向较大通孔尺寸倾斜时，增加的幅度会更大。此外，本文的结果表明，在某些条件下，通过改变整体柱通孔表面的zeta电位值，也可以实现带电分析物通量的相对适度增加。由于在聚合物整体柱合成过程中控制通孔尺寸分布的函数形式和宽度存在固有困难，通过谨慎选择离子交换表面官能团并通过流动相pH值进行微调来改变zeta电位值，似乎是增加带电分析物通量更实际的方法。因此，对于离子交换色谱系统，zeta电位可被视为柱设计者和操作者可操控的一个重要参数，因为改变它可以增加聚合物整体柱或填充带电颗粒的柱中带电分析物的通量。
