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首页> 外文学位 >Mixed-mode separations of cationic analytes on polybutadiene coated zirconia and octadecyl silane bonded silica phases.
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Mixed-mode separations of cationic analytes on polybutadiene coated zirconia and octadecyl silane bonded silica phases.

机译：聚丁二烯涂覆的氧化锆和十八烷基硅烷键合的硅胶相上阳离子分析物的混合模式分离。

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摘要

Octadecyl bonded silica-based (ODS) columns are by far the most popular stationary phases used in reversed phase liquid chromatography (RPLC) for the separations of basic compounds. The two major modes of interactions of such analytes on silica-based columns are hydrophobic and ion-exchange (Coulombic) interactions. The hydrocarbon of the bonded chains and the ionized residual silanol groups account for the hydrophobic and ion-exchange interactions, respectively.; Polybutadiene coated zirconia (PBD-ZrO2) is a new type of stationary phase characterized by its excellent chemical and thermal stability, as well as high efficiency. When hard Lewis bases, such as phosphate, are added to the eluent, they are adsorbed on the Lewis acid sites on zirconia's surface and cause the surface to become highly negatively charged. Under these conditions, the stationary phase acquires both reversed-phase and ion-exchange characteristics, qualitatively similar to silica-based phases, but quantitatively quite different.; Although the influence of hydrophobic and Coulombic interactions on the chromatography of cationic species is qualitatively well recognized, the quantitative relationship between hydrophobic and ion-exchange interactions remains unclear. The retention mechanisms on ODS and PBD-ZrO 2 phases were studied with a specific set of judiciously selected basic compounds, namely a homologous series of p-alkylbenzylamines (R-C6H4-CH2-NH2). Various quantitative models of mixed-mode retention mechanism on the two types of phases were compared and evaluated. The one-site model in which hydrophobic and Coulombic interactions combine has been disproved. Furthermore, the model equations developed allow us to, for the first time, quantify the relative amount of hydrophobic and Coulombic contributions to retention of any solute on any stationary phase. The data on both ODS and PBD-ZrO2 point to a multi-site model. The results clearly show that while ion-exchange plays an important but minor role (1--10%) on retention of bases on ODS phases, it is by far the dominant factor (>90% in some cases) in retention on PBD-ZrO2. The results also explain the very high sensitivity of PBD-ZrO2 phases compared to silica-based phases to the structure and type (primary, etc.) of the amine solute.
机译：迄今为止，十八烷基键合硅胶基（ODS）色谱柱是反相液相色谱（RPLC）中用于分离碱性化合物的最受欢迎的固定相。此类分析物在硅胶柱上的相互作用的两种主要模式是疏水和离子交换（库仑）相互作用。键合链的烃和离子化的残留硅烷醇基分别负责疏水和离子交换相互作用。聚丁二烯包覆的氧化锆（PBD-ZrO2）是一种新型固定相，具有出色的化学和热稳定性以及高效率。当将硬的路易斯碱（例如磷酸盐）添加到洗脱液中时，它们会吸附在氧化锆表面的路易斯酸位上，并使表面带高负电荷。在这些条件下，固定相既具有反相特性又具有离子交换特性，在质量上与二氧化硅基相相似，但在数量上完全不同。尽管疏水性和库仑性相互作用对阳离子物质色谱的影响已得到定性公认，但疏水性和离子交换相互作用之间的定量关系仍不清楚。使用一组经过慎重选择的特定碱性化合物（即对烷基苄胺的同源系列（R-C6H4-CH2-NH2））研究了ODS和PBD-ZrO 2相的保留机理。比较和评估了两种类型的混合模式保留机制的各种定量模型。疏水和库仑相互作用结合的单点模型已被证明。此外，开发的模型方程式使我们首次可以量化疏水性和库仑性对固定相上任何溶质保留的相对量。 ODS和PBD-ZrO2上的数据都指向一个多站点模型。结果清楚地表明，尽管离子交换对碱在ODS相上的保留作用起着重要但次要的作用（1--10％），但到目前为止，它仍是对PBD-保留的主导因素（在某些情况下> 90％）。氧化锆结果也解释了与基于二氧化硅的相相比，PBD-ZrO2相对胺溶质的结构和类型（伯等）具有很高的敏感性。

著录项

  • 作者

    Yang, Xiqin.;

  • 作者单位

    University of Minnesota.;

  • 授予单位 University of Minnesota.;
  • 学科 Chemistry Analytical.
  • 学位 Ph.D.
  • 年度 2004
  • 页码 262 p.
  • 总页数 262
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 化学;
  • 关键词

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