van den Heuvel Remco, Sutherland Ian
Brunel Institute for Bioengineering, Brunel University, Uxbridge, UK.
J Chromatogr A. 2009 May 8;1216(19):4252-7. doi: 10.1016/j.chroma.2008.11.069. Epub 2008 Nov 30.
Flow visualisation is essential when trying to understand hydrodynamic equilibrium in continuous counter-current extraction (CCCE) (also known as dual-flow counter-current chromatography). The technique allows two immiscible liquid phases to be pumped through the spinning coil simultaneously in opposite directions. When this process was described previously it was assumed that the phases were evenly distributed throughout the coil. Visualisation studies by van den Heuvel and Sutherland in 2007 showed that this was not the case. A special centrifuge, where the coil is cantilevered so that the coil and the fluids inside the coil can be visualised, was used to study the distribution of the phases. Factorial experimental design was used to systematically study the effect of the starting conditions inside the coil on the phase distribution at equilibrium. For each experiment the eluted volumes and the volume of upper phase in the coil at the end of the experiment (at equilibrium) were recorded. In addition, two photographs were taken when the phases in the coil had reached equilibrium. One of these photographs was taken during the experiment when the phases were still being pumped through and one when the flow was stopped. The systematic experiments showed that the initial phase inside the coil has no effect on the phase distribution achieved at equilibrium. Statistical analysis also showed that the lower phase flow rate has double the effect on the phase distribution compared to the upper phase flow rate. From these visualisation studies, it can be concluded that the balance of the phases flowing through the coil at equilibrium is complex. The volumes of upper and lower phase and how they are distributed does influence the separation. It is important therefore to understand the relationship between respective flow rates and the phase distribution if peak elution is to be accurately predicted.
在试图理解连续逆流萃取（CCCE）（也称为双流逆流色谱法）中的流体动力学平衡时，流动可视化至关重要。该技术允许两种互不相溶的液相同时以相反方向泵入旋转盘管。先前描述此过程时，假定各相在盘管中均匀分布。2007年范登·霍伊维尔和萨瑟兰的可视化研究表明情况并非如此。使用一种特殊的离心机，其中盘管呈悬臂式，以便可以观察盘管及其内部的流体，来研究各相的分布。采用析因实验设计来系统研究盘管内部的起始条件对平衡时相分布的影响。对于每个实验，记录洗脱体积以及实验结束时（平衡时）盘管中上层相的体积。此外，当盘管中的相达到平衡时拍摄两张照片。其中一张照片是在实验过程中各相仍在泵送时拍摄的，另一张是在流动停止时拍摄的。系统实验表明，盘管内部的初始相对平衡时实现的相分布没有影响。统计分析还表明，下层相流速对相分布的影响是上层相流速的两倍。从这些可视化研究可以得出结论，平衡时流经盘管的各相的平衡是复杂的。上层相和下层相的体积及其分布方式确实会影响分离。因此，如果要准确预测峰洗脱，则了解各自流速与相分布之间的关系很重要。
