Differential Scanning Calorimetry of Reversed-Phase LC Packings
Differential Scanning Calorimetry of Reversed-Phase LC Packings
复制标题
反相 LC 填料的差示扫描量热法
DOI：
10.1093/chromsci/21.12.560
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发表时间：
1983
影响因子：
1.3
通讯作者：
J. Callis
中科院分区：
文献类型：
--
作者：
Sonja J. Hansen;J. Callis
差示扫描量热法是用来探测反相液相色谱填料的烷基表面的超分子结构的各个方面。在这些研究中使用了三种类型的材料：材料A，常规的化学键合的C18和C22填料，覆盖率约为2.0 - 2.5微摩尔/m2;材料B，与A相同的化学键合填料，但以约1：1的比例补充有游离的C18或C22正烷烃;和材料C，高表面积的SiO2颗粒，C18和C22正构烷烃以足够的密度物理吸附，以产生最紧密堆积的单层覆盖。毫不奇怪，材料A未能给出明显的相变。在这里，链的密度使得链间力太弱而不能提供有序相。相比之下，材料B给出了明显的相变，其发生在较低的温度Tm下，并且具有比纯烷烃观察到的更小的焓ΔHm。材料C也给出了明显的相变，其Tmand Δ Hm的值与材料B的值相当。最后，DSC用于证明结合到反相的有机改性剂层的存在。
Differential scanning calorimetry is used to probe various aspects of the supramolecular structure of the alkyl surface of reversed-phase liquid chromatography packings. Three types of materials were employed in these studies: materials A, conventional chemically bonded C18and C22packings at coverages of about 2.0 to 2.5 micromoles/m2; materials B, the same chemically bonded packings as A, but supplemented with free C18or C22n-alkanes at approximately 1:1 ratio; and materials C, high surface area SiO2particulates to which C18and C22n-alkanes were physically adsorbed at sufficient densities to yield closest-packed monolayer coverages. Not surprisingly, materials A failed to give distinct phase transitions. Here the density of the chains is such that interchain forces are too weak to provide an ordered phase. In contrast, materials B gave distinct phase transitions which occurred at a lower temperature, Tm, and with smaller enthalpy, ΔHm, than those observed for the pure alkanes. Materials C also gave distinct phase transitions, with values for Tmand ΔHmcomparable to those of materials B. Finally, DSC was used to demonstrate the presence of a layer of organic modifier bound to the reversed phase.