Institute of Thermal Separation Processes, Hamburg University of Technology, Eißendorfer Straße 38, 21073 Hamburg, Germany.
Institute of Thermal Separation Processes, Hamburg University of Technology, Eißendorfer Straße 38, 21073 Hamburg, Germany.
J Chromatogr A. 2019 Mar 15;1588:127-136. doi: 10.1016/j.chroma.2018.12.053. Epub 2018 Dec 26.
In this work, inverse supercritical fluid chromatography was applied to characterize the surface of four silica materials (three commercial Kromasils and one silica aerogel) from chromatographic retention data. Retention factors at various pressures (150-300 bar), temperatures (25-60 °C) and modifier concentrations (5-20 vol.% methanol in CO) for a set of representative 17 solutes were correlated with the solute properties by the linear solvation energy relationships (LSER). Two types of the LSER models were identified based on different criteria. Firstly, a generally valid model with two descriptors concerning dipolarity/polarizability and solute hydrogen-bonding acceptor ability was constructed. Secondly, a group of specific models for each particular silica material was proposed. According to the statistical analysis of the modeling results, the acid-basic interactions were demonstrated to have a major contribution to the retention for all studied silicas. The intensity of these interactions decreases with increasing methanol concentration in the mobile phase, possibly due to the mixed mechanism of competitive adsorption of the modifier on silanol groups and modification of mobile phase property. Moreover, retention factors measured under constant conditions (p, T, methanol concentration) for a pair of the materials were found to be proportional in logarithmic scale implying the transferability of the adsorption free energies and the adsorption constants across four studied silica materials.
在这项工作中,反超临界流体色谱法被应用于从色谱保留数据来表征四种硅胶材料(三种商业 Kromasil 和一种硅胶气凝胶)的表面。在各种压力(150-300 巴)、温度(25-60°C)和改性剂浓度(CO 中的 5-20 体积%甲醇)下,一组代表性的 17 种溶质的保留因子与溶质性质通过线性溶剂化能关系(LSER)相关联。根据不同的标准,确定了两种类型的 LSER 模型。首先,构建了一个具有两个描述符(偶极矩/极化率和溶质氢键接受能力)的通用有效模型。其次,为每种特定的硅胶材料提出了一组特定的模型。根据建模结果的统计分析,表明对于所有研究的硅胶,酸-碱相互作用对保留有主要贡献。随着流动相甲醇浓度的增加,这些相互作用的强度降低,这可能是由于改性剂在硅醇基团上的竞争吸附和流动相性质的改性的混合机制所致。此外,在恒定条件(p、T、甲醇浓度)下测量的一对材料的保留因子在对数尺度上呈比例关系,这意味着吸附自由能和吸附常数在四种研究的硅胶材料之间具有可转移性。