Division of Metabolomics, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan; Vrije Universiteit Brussel, Department of Chemical Engineering, Pleinlaan 2, B-1050, Brussels, Belgium.
Vrije Universiteit Brussel, Department of Chemical Engineering, Pleinlaan 2, B-1050, Brussels, Belgium.
J Chromatogr A. 2018 Jun 1;1552:87-91. doi: 10.1016/j.chroma.2018.03.050. Epub 2018 Mar 29.
We report on a modification in the hydrothermal treatment process of monolithic silica layers used in porous-layered open tubular (PLOT) columns. Lowering the temperature from the customary 95 °C to 80 °C, the size of the mesopores reduced by approximately about 35% from 12-13.5 nm to 7.5-9 nm, while the specific pore volume essentially remains unaltered. This led to an increase of the specific surface area (SA) of about 40%, quasi-independent of the porous layer thickness. The increased surface area provided a corresponding increase in retention, somewhat more (48%) than expected based on the increase in SA for the thin layer columns, and somewhat less than expected (34%) for the thick layer columns. The recipes were applied in 5 μm i.d.-capillaries with a length of 60 cm. Efficiencies under retained conditions amounted up to N = 137,000 for the PLOT column with a layer thickness (d) of 300 nm and to N = 109,000 for the PLOT column with d = 550 nm. Working under conditions of similar retention, the narrow pore/high SA columns produced with the new 80 °C recipe generated the same number of theoretical plates as the wide pore size/low SA columns produced with the 95 °C recipe. This shows the 80 °C-hydrothermal treatment process allows for an increase in the phase ratio of the PLOT columns without affecting their intrinsic mass transfer properties and separation kinetics. This is further corroborated by the fact that the plate height curves generated with the new and former recipe can both be well-fitted with the Golay-Aris equation without having to change the intra-layer diffusion coefficient.
我们报告了一种用于多孔层开管（PLOT）柱的整体硅胶层的水热处理工艺的改进。将温度从通常的 95°C 降低到 80°C，介孔的尺寸从 12-13.5nm 减小到 7.5-9nm，而比孔体积基本保持不变。这导致比表面积（SA）增加了约 40%，几乎与多孔层厚度无关。增加的表面积提供了相应的保留增加，比基于薄层柱的 SA 增加（48%）略高，比厚层柱（34%）略低。该配方应用于内径为 5μm 的毛细管中，长度为 60cm。在保留条件下，厚度为 300nm 的 PLOT 柱的效率高达 N=137,000，厚度为 550nm 的 PLOT 柱的效率高达 N=109,000。在相似保留条件下工作时，用新的 80°C 配方制备的窄孔径/高 SA 柱与用 95°C 配方制备的宽孔径/低 SA 柱产生的理论塔板数相同。这表明 80°C 的水热处理过程允许在不影响其内在传质性能和分离动力学的情况下增加 PLOT 柱的相比例。这进一步得到了以下事实的证实，即新配方和旧配方生成的板高曲线都可以用 Golay-Aris 方程很好地拟合，而无需改变层内扩散系数。
