Fluid dynamics in capillary and chip electrochromatography
Fluid dynamics in capillary and chip electrochromatography
复制标题
DOI：
10.1002/elps.200600625
复制
发表时间：
2007-02
期刊：
影响因子：
2.9
通讯作者：
I. Nischang;U. Tallarek
中科院分区：
文献类型：
--
作者：
I. Nischang;U. Tallarek
本文综述了高比表面积随机多孔介质作为固定相的毛细管和芯片电色谱（EC）中的唯象流体动力学。具体而言，相对于局部和宏观的不均匀性，以及可实现的分离效率的填充床和整料的孔隙空间形态进行了分析。首先指出，通过填充床和整料的孔隙级速度分布通常是不均匀的。这与单一均匀通道中的塞状微扰分布形成对比，并且是由于连续会聚和发散孔导致多孔介质中局部电场强度的不均匀分布引起的。几何和电动性质的壁效应形成了填充床中颗粒不均匀性的另一个来源，这是由硬颗粒对着具有不同zeta电位的硬壁填充引起的。在低的柱-颗粒直径比下，在几个颗粒直径的距离上靠近限制壁的系统孔隙度波动的影响变得更加严重。由于填充床和基于二氧化硅的整料中的孔隙空间的分级结构（其特征在于离散的颗粒内（骨架内）介孔和颗粒间（骨架间）大孔空间域），在大多数一般条件下，多孔颗粒和整料骨架内普遍存在电荷选择性传输。它形成了电场诱导浓差极化（CP）的基础。同时，在这些分层结构的材料中实现了有限的并且-取决于形态学-通常是显著的灌注性微结构。在这篇评论中收集的数据表明，CP的存在和它的相对强度相比，灌注式的基本成分，调整EC采用整料和填充床作为固定相的流体动力学。这解决了（电）流体动力学，相关的流体动力学分散，以及带电分析物的迁移和保留。
This review is concerned with the phenomenological fluid dynamics in capillary and chip electrochromatography (EC) using high‐surface‐area random porous media as stationary phases. Specifically, the pore space morphology of packed beds and monoliths is analyzed with respect to the nonuniformity of local and macroscopic EOF, as well as the achievable separation efficiency. It is first pointed out that the pore‐level velocity profile of EOF through packed beds and monoliths is generally nonuniform. This contrasts with the plug‐like EOF profile in a single homogeneous channel and is caused by a nonuniform distribution of the local electrical field strength in porous media due to the continuously converging and diverging pores. Wall effects of geometrical and electrokinetic nature form another origin for EOF nonuniformities in packed beds which are caused by packing hard particles against a hard wall with different zeta potential. The influence of the resulting, systematic porosity fluctuations close to the confining wall over a distance of a few particle diameters becomes aggravated at low column‐to‐particle diameter ratio. Due to the hierarchical structure of the pore space in packed beds and silica‐based monoliths which are characterized by discrete intraparticle (intraskeleton) mesoporous and interparticle (interskeleton) macroporous spatial domains, charge‐selective transport prevails within the porous particles and the monolith skeleton under most general conditions. It forms the basis for electrical field‐induced concentration polarization (CP). Simultaneously, a finite and – depending on morphology – often significant perfusive EOF is realized in these hierarchically structured materials. The data collected in this review show that the existence of CP and its relative intensity compared to perfusive EOF form fundamental ingredients which tune the fluid dynamics in EC employing monoliths and packed beds as stationary phases. This addresses the (electro)hydrodynamics, associated hydrodynamic dispersion, as well as the migration and retention of charged analytes.