Plocková Jana, Chmelík Josef
Institute of Analytical Chemistry, AS CR, 611 42 Brno, Czech Republic.
J Chromatogr A. 2006 Jun 23;1118(2):253-60. doi: 10.1016/j.chroma.2006.03.124. Epub 2006 May 11.
In previous papers, several approaches to programming of the resulting force field in GFFF were described and investigated. The experiments were dealing with flow-velocity and channel thickness, i.e. factors influencing hydrodynamic lift forces (HLF). The potential of density and viscosity of carrier liquid for field programming was predicted and demonstrated by preliminary experiments. This work is devoted to experimental verification of the influence of carrier liquid density and viscosity. Several carrier liquid density and simultaneously viscosity gradients using water-methanol mixtures are in this work implemented in the separation of a model silica mixture. Working with the water-methanol gradients, one is not able to separate the influence of density from the contribution of viscosity. However, we found experimental conditions to show the isolated effect of carrier liquid density (two water-methanol mixtures of equal viscosity differing in their densities). In order to demonstrate the isolated effect of viscosity, we implemented in this work a new system of (hydroxypropyl)methyl cellulose (HPMC) carrier liquids. Three different HPMC compositions enabled to vary the viscosity more than two times at almost constant density. With increasing carrier liquid viscosity, the focusing and elevating trend was clearly pronounced for 5 and 10 microm silica particles. By the isolated effect of increased viscosity, the centre of the 10 microm particle zone was elevated to the streamline at 16% of the channel height. These experiments have shown that the influence of carrier liquid viscosity on HLF should be taken into account even at higher levels above the channel bottom, i.e. beyond the near-wall region. Further, it is shown that higher value of carrier liquid viscosity improves the separation of the model mixture in terms of time and resolution.
在之前的论文中，描述并研究了几种在重力场流分聚焦（GFFF）中对所得力场进行编程的方法。实验涉及流速和通道厚度，即影响流体动力升力（HLF）的因素。通过初步实验预测并证明了载液密度和粘度对场编程的潜力。这项工作致力于对载液密度和粘度影响的实验验证。在模型二氧化硅混合物的分离中，使用水 - 甲醇混合物实现了几种载液密度以及同时的粘度梯度。使用水 - 甲醇梯度时，无法区分密度的影响和粘度的贡献。然而，我们找到了实验条件来展示载液密度的孤立效应（两种粘度相同但密度不同的水 - 甲醇混合物）。为了证明粘度的孤立效应，我们在这项工作中采用了一种新的（羟丙基）甲基纤维素（HPMC）载液体系。三种不同的HPMC组成能够在几乎恒定的密度下使粘度变化超过两倍。随着载液粘度的增加，对于5微米和10微米的二氧化硅颗粒，聚焦和提升趋势明显。通过增加粘度的孤立效应，10微米颗粒区的中心升高到通道高度16%处的流线。这些实验表明，即使在通道底部上方较高的位置，即超出近壁区域，也应考虑载液粘度对HLF的影响。此外，结果表明，较高的载液粘度值在时间和分辨率方面改善了模型混合物的分离效果。
