Solvent viscosity mismatch between the solute plug and the mobile phase: Considerations in the applications of two-dimensional HPLC

摘要

Understanding the nature of viscosity contrast induced flow instabilities is an important aspect innthe design of two-dimensional HPLC separations. When the viscosity contrast between the sample plugnand the mobile phase is sufficiently large, the phenomenon known as viscous fingering can be induced.nViscous fingering is a flow instability phenomenon that occurs at the interface between two fluids withndifferent viscosities. In liquid chromatography, viscous fingering results in the solute band undergoingna change in form as it enters into the chromatography column. Moreover, even in the absence ofnviscous fingering, band shapes change shape at low viscosity contrasts. These changes can result inna noticeable change in separation performance, with the result depending on whether the solventnpushing the solute plug has a higher or lower viscosity than the solute plug. These viscosity inducednchanges become more important as the solute injection volume increases and hence understanding thenprocess becomes critical in the implementation of multidimensional HPLC techniques, since in thesentechniques the sample injection plug into the second dimension is an order of magnitude greater than innone-dimensional HPLC. This review article assesses the current understanding of the viscosityncontrast induced processes as they relate to liquid chromatographic separation behaviour.