Gustavus Adolphus College, 800 West College Avenue, St. Peter, MN 56082, United States of America.
Agilent Technologies R&D and Marketing GmbH & Co KG, Hewlett-Packard-Str. 8, Waldbronn, 76337, Germany.
J Chromatogr A. 2015 Jan 23;1378:50-7. doi: 10.1016/j.chroma.2014.12.019. Epub 2014 Dec 12.
Users of online comprehensive two-dimensional liquid chromatography (LCxLC) frequently acknowledge that the mechanical instability of HPLC columns installed in these systems, particularly in the second dimension, is a significant impediment to its use. Such instability is not surprising given the strenuous operating environment to which these columns are subjected, including the large number (thousands per day) of fast and large pressure pulses resulting from interface valve switches (on the timescale of tens of milliseconds) associated with very fast second dimension separations. There appear to be no published reports of systematic studies of the relationship between second dimension column lifetime and any of these variables. In this study we focused on the relationship between the lifetimes of commercially available columns and the pressure pulses observed at the inlet of the second dimension column that occur during the switching of the valve that interfaces the two dimensions of a LCxLC system. We find that the magnitude of the pressure drop at the inlet of the second dimension column during the valve switch, which may vary between 10 and 95% of the column inlet pressure, is dependent on valve switching speed and design, and has a dramatic impact on column lifetime. In the worst case, columns fail within the first few hours of use in an LCxLC system. In the best case, using a valve that exhibits much smaller pressure pulses, the same columns exhibit much improved lifetimes and have been used continuously under LCxLC conditions for several days with no degradation in performance. This result represents a first step in understanding the factors that affect second dimension column lifetime, and will significantly improve the usability of the LCxLC technique in general.
使用在线二维液相色谱（LCxLC）的用户经常会承认，安装在这些系统中的 HPLC 柱（尤其是二维柱）的机械不稳定性是其使用的一个重大障碍。考虑到这些柱子所处的恶劣操作环境，包括接口阀切换（在几十毫秒的时间尺度上）产生的大量（每天数千个）快速且高压脉冲，这种不稳定性并不奇怪，这些快速且高压脉冲与非常快速的二维分离有关。似乎没有关于二维柱寿命与这些变量之间关系的系统研究的已发表报告。在这项研究中，我们专注于商业上可用的柱子的寿命与在 LCxLC 系统的二维接口处的阀切换期间观察到的第二维柱入口处的压力脉冲之间的关系。我们发现，在阀切换期间第二维柱入口处的压降幅度（可能在柱入口压力的 10%到 95%之间变化）取决于阀切换速度和设计，并且对柱寿命有重大影响。在最坏的情况下，柱子在 LCxLC 系统中使用的前几个小时内就会失效。在最好的情况下，使用表现出较小压力脉冲的阀，相同的柱子的寿命大大提高，并且在 LCxLC 条件下连续使用数天而没有性能下降。这一结果代表了理解影响二维柱寿命的因素的第一步，将大大提高 LCxLC 技术的可用性。
