Vrije Universiteit Brussel, Department of Chemical Engineering (CHIS-IR), Pleinlaan 2, 1050 Brussels, Belgium.
J Chromatogr A. 2010 Mar 26;1217(13):2022-31. doi: 10.1016/j.chroma.2010.01.072. Epub 2010 Jan 29.
A generic solution is proposed for the deleterious viscous heating effects in adiabatic or near-adiabatic systems that can be expected when trying to push the column operating pressures above the currently available range of ultra-high pressures (i.e., 1200 bar). A set of proof-of-principle experiments, mainly using existing commercial equipment, is presented. The solution is based on splitting up a column with given length L into n segments with length L/n, and providing an active cooling to the capillaries connecting the segments. In this way, the viscous heat is removed at a location where the radial heat removal does not lead to an efficiency loss (i.e., in the thin connection capillaries), while the column segments can be operated under near-adiabatic conditions without suffering from an unacceptable rise of the mobile phase temperature. Experimental results indicate that the column segmentation does not lead to a significant efficiency loss (comparing the performance of a 10 cm column with a 2 cm x 5 cm column system), whereas, as expected, the system displays a much improved temperature stability, both in time (because of the shortened temperature transient times) and in space (reduction of the average axial temperature rise by a factor n). The method also prevents a large backflow of heat along the column wall that would lead to large efficiency losses if one would attempt to operate columns at pressures of 1500 bar or more. A real-world pharmaceutical example is given where this improved temperature robustness could help in moderating the changes in selectivity during method transfer from a low to a high pressure operation, although the complex non-linear behavior of the viscous heating and high pressure effects result in lower than expected improvement.
提出了一种通用的解决方案，用于解决在试图将柱操作压力推高到目前可用的超高压力范围（即 1200 巴）以上时，绝热或近绝热系统中可能出现的有害粘性加热效应。本文介绍了一组原理验证实验，主要使用现有的商业设备。该解决方案基于将具有给定长度 L 的柱分成 n 段，每段长度为 L/n，并对连接段的毛细管进行主动冷却。这样，粘性热就会在径向热移除不会导致效率损失的位置（即在薄连接毛细管中）被移除，而柱段可以在近绝热条件下运行，而不会遭受流动相温度不可接受的升高。实验结果表明，柱分段不会导致明显的效率损失（比较 10cm 柱和 2cmx5cm 柱系统的性能），而正如预期的那样，该系统显示出更好的温度稳定性，无论是在时间上（由于缩短了温度瞬变时间）还是在空间上（通过因子 n 降低平均轴向温度升高）。该方法还防止了大量的热沿着柱壁回流，如果试图在 1500 巴或更高的压力下操作柱，这将导致大量的效率损失。本文提供了一个实际的制药示例，其中这种改进的温度鲁棒性可以帮助在从低压到高压操作的方法转移过程中缓和选择性的变化，尽管粘性加热和高压效应的复杂非线性行为导致的改进低于预期。
