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首页> 外文期刊>Chemistry: A European journal >Revealing the Fine Details of Functionalized Silica Surfaces by Solid-State NMR and Adsorption Isotherm Measurements: The Case of Fluorinated Stationary Phases for Liquid Chromatography
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Revealing the Fine Details of Functionalized Silica Surfaces by Solid-State NMR and Adsorption Isotherm Measurements: The Case of Fluorinated Stationary Phases for Liquid Chromatography

机译：通过固态NMR和吸附等温线测量揭示功能化二氧化硅表面的精细细节：液相色谱氟化固定相的情况

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摘要

The structural and chromatographic characterization of two novel fluorinated mesoporous materials prepared by covalent reaction of 3-(pentafluorophenyl)propyldimethylchlorosilane and perfluorohexylethyltrichlorosilane with 2.5 mm fully porous silica particles is reported. The adsorbents were characterized by solid state ~(29)Si, ~(13)C, and ~(19)F NMR spectroscopy, low-temperature nitrogen adsorption, elemental analysis (C and F), and various chromatographic measurements, including the determination of adsorption isotherms. The structure and abundance of the different organic surface species, as well as the different silanol types, were determined. In particular, the degree of so-called horizontal polymerization, that is, Si-O-Si bridging parallel to the silica surface due to the reaction, under "quasi-dry" conditions, of trifunctional silanizing agents with the silica surface was quantified. Significant agreement was found between the information provided by solid-state NMR, elemental analysis, and excess isotherms regarding the amount of surface residual silanol groups, on the one hand, and the degree of surface functionalization, on the other. Finally, the kinetic performance of the fluorinated materials as separation media for applications in near-ultrahigh-performance liquid chromatography was evaluated. At reduced velocities of about 5.5 (ca. 600 bar backpressure at room temperature) with 3 mm diameter columns and toluene as test compound, reduced plate heights on the order of 2 were obtained on columns of both adsorbents.
机译：报道了通过3-（五氟苯基）丙基二甲基氯硅烷和全氟己基乙基三氯硅烷与2.5 mm全多孔二氧化硅粒子共价反应制备的两种新型氟化介孔材料的结构和色谱特性。吸附剂的特征在于固态〜（29）Si，〜（13）C和〜（19）F NMR光谱，低温氮吸附，元素分析（C和F）以及各种色谱测量，包括测定吸附等温线。确定了不同有机表面物种的结构和丰度，以及不同的硅​​烷醇类型。特别地，定量了所谓的水平聚合度，即，由于在准干燥条件下三官能硅烷化剂与二氧化硅表面反应而平行于二氧化硅表面的Si-O-Si桥接。固态NMR，元素分析和过量等温线提供的信息一方面与表面残留硅烷醇基团的数量有关，另一方面与表面官能化程度有关。最后，评估了氟化材料作为分离介质的动力学性能，用于近超高效液相色谱。用直径为3 mm的色谱柱和甲苯作为测试化合物，在约5.5的降低速度下（室温下约600 bar的背压），在两种吸附剂的色谱柱上均获得了约2数量级的塔板高度降低。

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