Poe Donald P, Schroden Jonathan J
Department of Chemistry and Biochemistry, University of Minnesota Duluth, 10 University Drive, Duluth, MN 55812, USA.
J Chromatogr A. 2009 Nov 6;1216(45):7915-26. doi: 10.1016/j.chroma.2009.08.089. Epub 2009 Sep 6.
The effects of particle size and thermal insulation on retention and efficiency in packed-column supercritical fluid chromatography with large pressure drops are described for the separation of a series of model n-alkane solutes. The columns were 2.0mm i.d.x150mm long and were packed with 3, 5, or 10-mum porous octylsilica particles. Separations were performed with pure carbon dioxide at 50 degrees C at average mobile phase densities of 0.47g/mL (107bar) and 0.70g/mL (151bar). The three principal causes of band broadening were the normal dispersion processes described by the van Deemter equation, changes in the retention factor due to the axial density gradient, and radial temperature gradients associated with expansion of the mobile phase. At the lower density the use of thermal insulation resulted in significant improvements in efficiency and decreased retention times at large pressure drops. The effects are attributed to the elimination of radial temperature gradients and the concurrent enhancement of the axial temperature gradient. Thermal insulation had no significant effect on chromatographic performance at the higher density. A simple expression to predict the onset of excess efficiency loss due to the radial temperature gradient is proposed.
描述了粒径和热绝缘对具有大压降的填充柱超临界流体色谱中保留和效率的影响，用于分离一系列正构烷烃模型溶质。色谱柱内径为2.0mm，长150mm，填充有3、5或10μm的多孔辛基硅胶颗粒。在50℃下用纯二氧化碳进行分离，平均流动相密度为0.47g/mL（107bar）和0.70g/mL（151bar）。谱带展宽的三个主要原因是范德姆特方程描述的正常扩散过程、由于轴向密度梯度导致的保留因子变化以及与流动相膨胀相关的径向温度梯度。在较低密度下，使用热绝缘可显著提高效率，并在大压降下缩短保留时间。这些影响归因于径向温度梯度的消除和轴向温度梯度的同时增强。热绝缘在较高密度下对色谱性能没有显著影响。提出了一个简单的表达式来预测由于径向温度梯度导致的额外效率损失的起始点。
