Institute of Physical Chemistry, Justus Liebig University of Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany.
J Chromatogr A. 2011 Jun 10;1218(23):3624-35. doi: 10.1016/j.chroma.2011.04.008. Epub 2011 Apr 12.
Monolithic silica capillary columns with i.d. 100 μm and monolithic silica rods were prepared with tetramethoxysilane (TMOS) or a mixture of TMOS and metyltrimethoxysilane (MTMS) using different hydrothermal treatments at T=80 °C or 120 °C. Nitrogen physisorption was applied for the pore characterization of the rods and inverse size exclusion chromatography (ISEC) for that of the capillary columns. Using nitrogen physisorption, it was shown change of pore size and surface area corresponds to that of hydrothermal treatment and silica precursor. The results from ISEC agreed well with those from nitrogen physisorption regarding the pore size distribution (PSD). In addition, the retention factors for hexylbenzene with the ODS-modified capillary columns in methanol/water=80/20 at T=30 °C could also support the results from nitrogen physisorption. Furthermore, column efficiency for the columns was evaluated with alkylbenzenes and three kinds of peptides, leucine-enkephalin, angiotensin II, and insulin. Column efficiency for alkylbenzenes was similar independently of the hydrothermal treatment at T=120 °C. Even for TMOS columns, there was no significant difference in column efficiency for the peptides despite the difference in hydrothermal treatment. In contrast, for hybrid columns, it was possible to confirm the effect on hydrothermal treatment at T=120 °C resulting in a different column efficiency, especially for insulin. This difference supports the results from both nitrogen physisorption and ISEC, showing the presence of more small pores of ca. 3-6 nm for a hybrid silica without hydrothermal treatment at T=120 °C. Consequently, the results suggest that hydrothermal treatment for a hybrid column with higher temperature or longer time is necessary, compared to that for a TMOS column, to provide higher column efficiency with increase in molecular size of solute.
使用四甲氧基硅烷（TMOS）或 TMOS 与甲基三甲氧基硅烷（MTMS）的混合物，分别在 80°C 或 120°C 下进行不同的水热处理，制备了内径为 100μm 的整体式硅胶毛细管柱和整体式硅胶棒。采用氮气物理吸附法对棒材的孔结构进行了表征，采用反相尺寸排阻色谱（ISEC）对毛细管柱的孔结构进行了表征。氮气物理吸附表明，孔径和比表面积的变化与水热处理和硅烷前体相对应。ISEC 的结果与氮气物理吸附的结果在孔径分布（PSD）方面非常吻合。此外，在 30°C 下甲醇/水=80/20 时，用 ODS 修饰的毛细管柱对己基苯的保留因子也支持氮气物理吸附的结果。此外，还使用烷基苯和三种肽（亮啡肽、血管紧张素 II 和胰岛素）评估了柱的柱效。在 120°C 下水热处理时，烷基苯的柱效相似。即使对于 TMOS 柱，尽管水热处理条件不同，但肽的柱效也没有显著差异。相比之下，对于杂化柱，可以确认在 120°C 下水热处理的效果，导致柱效不同，尤其是对胰岛素。这种差异支持了氮气物理吸附和 ISEC 的结果，表明在未经 120°C 水热处理的杂化硅胶中存在更多约 3-6nm 的小孔。因此，与 TMOS 柱相比，对于具有更高温度或更长时间的水热处理的杂化柱，需要进行水热处理，以提供更高的柱效和增加溶质的分子尺寸。
