Department of Analytical Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, CZ-53210 Pardubice, Czech Republic.
J Chromatogr A. 2010 Sep 24;1217(39):6052-60. doi: 10.1016/j.chroma.2010.07.019. Epub 2010 Jul 16.
Combined effects of temperature and mobile phase on the reversed phase chromatographic behavior of alkylbenzenes and simple substituted benzenes were investigated on a Blaze C8 polydentate silica-based column, showing improved resistance against hydrolytic breakdown at temperatures higher than 60 degrees C, in comparison to silica-based stationary phases with single attachment sites. For better insight into the retention mechanism on polydentate columns, we determined the enthalpy and entropy of the transfer of the test compounds from the mobile to the stationary phase. The enthalpic contribution dominated the retention at 80% or lower concentrations of methanol in the mobile phase. Entropic effects are more significant in 90% methanol and in acetonitrile-water mobile phases. Anomalies in the effects of mobile phase on the enthalpy of retention of benzene, methylbenzene and polar benzene derivatives were observed, in comparison to regular change in enthalpy and entropy of adsorption with changing concentration of organic solvent and the alkyl length for higher alkylbenzenes. The temperature and the mobile phase effects on the retention are practically independent of each other and--to first approximation--can be described by a simple model equation, which can be used for optimization of separation conditions.
烷基苯和简单取代苯在反相色谱中的保留行为受温度和流动相的综合影响，在 Blaze C8 多齿硅胶柱上进行了研究，与具有单附着位的硅胶固定相相比，该固定相在高于 60°C 的温度下具有更好的抗水解破坏能力。为了更好地了解多齿柱上的保留机制，我们测定了测试化合物从流动相转移到固定相的焓和熵。在流动相中甲醇浓度为 80%或更低时，焓贡献主导保留。在 90%甲醇和乙腈-水流动相中，熵效应更为显著。与随着有机溶剂浓度和较高烷基苯的烷基长度的变化而规律变化的吸附焓和熵相比，观察到了苯、甲基苯和极性苯衍生物在流动相作用下对保留焓的影响的异常。保留温度和流动相的影响彼此独立，并且——在第一近似程度上——可以用一个简单的模型方程来描述，该方程可用于优化分离条件。
