Australian Centre for Research on Separation Science, University of Western Sydney, NSW, Australia.
Analyst. 2010 Feb;135(2):222-9. doi: 10.1039/b908633c. Epub 2009 Dec 21.
Understanding the nature of viscosity contrast induced flow instabilities is an important aspect in the design of two-dimensional HPLC separations. When the viscosity contrast between the sample plug and the mobile phase is sufficiently large, the phenomenon known as viscous fingering can be induced. Viscous fingering is a flow instability phenomenon that occurs at the interface between two fluids with different viscosities. In liquid chromatography, viscous fingering results in the solute band undergoing a change in form as it enters into the chromatography column. Moreover, even in the absence of viscous fingering, band shapes change shape at low viscosity contrasts. These changes can result in a noticeable change in separation performance, with the result depending on whether the solvent pushing the solute plug has a higher or lower viscosity than the solute plug. These viscosity induced changes become more important as the solute injection volume increases and hence understanding the process becomes critical in the implementation of multidimensional HPLC techniques, since in these techniques the sample injection plug into the second dimension is an order of magnitude greater than in one-dimensional HPLC. This review article assesses the current understanding of the viscosity contrast induced processes as they relate to liquid chromatographic separation behaviour.
理解粘度对比引起的流动不稳定性的本质是二维 HPLC 分离设计的一个重要方面。当样品塞与流动相之间的粘度对比足够大时，会引起所谓的粘性指进现象。粘性指进是一种发生在两种粘度不同的流体界面处的流动不稳定性现象。在液相色谱中，粘性指进导致溶质带在进入色谱柱时发生形态变化。此外，即使没有粘性指进，在低粘度对比下，带形也会发生变化。这些变化会导致分离性能的显著变化，具体取决于推动溶质塞的溶剂的粘度是否高于或低于溶质塞。随着溶质进样体积的增加，这些由粘度引起的变化变得更加重要，因此，在多维 HPLC 技术的实施中，理解这一过程至关重要，因为在这些技术中，进入第二维的样品进样塞比一维 HPLC 中的进样塞大一个数量级。本文综述了目前对与液相色谱分离行为有关的粘度对比诱导过程的理解。
