van de Ven H C, Gargano A F G, van der Wal Sj, Schoenmakers P J
University of Amsterdam, Faculty of Science, Science Park 904, 1098 XH Amsterdam, The Netherlands; TA-COAST, Science Park 904, Amsterdam, The Netherlands.
University of Amsterdam, Faculty of Science, Science Park 904, 1098 XH Amsterdam, The Netherlands; TA-COAST, Science Park 904, Amsterdam, The Netherlands.
J Chromatogr A. 2016 Jan 4;1427:90-5. doi: 10.1016/j.chroma.2015.11.082. Epub 2015 Nov 30.
A novel approach to achieve solvent switching and focusing of sub-column-volume analyte fractions in liquid chromatography is presented. By altering the temperature between loading and elution in back-flush mode, solvent transfer of analytes and focusing occurs, provided that the analytes exhibit temperature dependent retention on a given trap column. When retention on the trap decreases with increasing temperature, which is almost always the case, the loading of the trap-column takes place at a higher temperature than the elution. This principle is demonstrated using three small aromatic molecules (toluene, p-xylene and benzophenone) on a capillary monolithic column. On this column, the analytes show a traditional van't Hoff dependence on temperature with enthalpy effects of, -15, -16 and -18 kJ mol(-1), respectively, for a mobile phase of 25% acetonitrile in water. The column was loaded at 110 °C, cooled in an ice bath and eluted in back-flush mode at 0 °C. When operated in this way, the analytes are transferred from the loading solvent to the elution solvent, achieving solvent switching. Substantial focusing can also be obtained if the desorption solvent is stronger than the loading solvent.
本文提出了一种在液相色谱中实现亚柱体积分析物馏分的溶剂切换和聚焦的新方法。通过在反冲模式下改变进样和洗脱之间的温度，只要分析物在给定的捕集柱上表现出温度依赖性保留，就会发生分析物的溶剂转移和聚焦。当捕集柱上的保留随着温度升高而降低时（几乎总是这种情况），捕集柱的进样在比洗脱更高的温度下进行。使用毛细管整体柱上的三种小芳香族分子（甲苯、对二甲苯和二苯甲酮）证明了这一原理。在该柱上，对于25%乙腈水溶液的流动相，分析物分别表现出传统的范特霍夫温度依赖性，焓效应分别为-15、-16和-18 kJ mol(-1)。柱子在110℃进样，在冰浴中冷却，并在0℃以反冲模式洗脱。以这种方式操作时，分析物从进样溶剂转移到洗脱溶剂，实现溶剂切换。如果解吸溶剂比进样溶剂更强，也可以获得显著的聚焦。
