Institute of Chemistry, University of Campinas, Campinas, SP, Brazil.
J Chromatogr A. 2011 Jul 15;1218(28):4378-88. doi: 10.1016/j.chroma.2011.05.007. Epub 2011 May 13.
Variations of a thermal immobilization procedure using poly(methyltetradecilsiloxane) and silica produced fourteen stationary phases with carbon contents of 4-18%. The stationary phases were chromatographically evaluated with the Engelhardt, SRM 870 and Tanaka tests. Classifications using USP and Euerby procedures indicate that the new immobilized phases are different from most commercial phases although there was some similarity with phases that have high ion-exchange interactions. The retention mechanism involved in the separation of basic solutes on several of the new stationary phases was studied by varying pH, type of Lewis base and the ionic strength of the eluent. The separations are strongly influenced by the chemistry of the accessible free silanols. The stationary phases present good selectivity at intermediate pH where the basic analytes were protonated, suggesting use of intermediate pH for these separations. Stability tests show that the stationary phases have poor stability at very high pH, even at 23°C, but good stability in acidic mobile phases, even at 75°C, as expected for an immobilized polymer stationary phase.
使用聚（甲基十四烷基硅氧烷）和二氧化硅的热固定程序的变化产生了十四种固定相，其碳含量为 4-18%。使用 Engelhardt、SRM 870 和 Tanaka 测试对固定相进行了色谱评估。使用 USP 和 Euerby 程序进行的分类表明，尽管与具有高离子交换相互作用的固定相有些相似，但新型固定相与大多数商业固定相不同。在几种新型固定相上分离碱性溶质的保留机制通过改变 pH 值、路易斯碱的类型和洗脱液的离子强度进行了研究。分离受可及的游离硅醇的化学性质强烈影响。在中间 pH 值下，固定相具有良好的选择性，此时碱性分析物被质子化，这表明这些分离可以在中间 pH 值下进行。稳定性测试表明，固定相在非常高的 pH 值（即使在 23°C 下）下稳定性较差，但在酸性流动相中稳定性良好，即使在 75°C 下也稳定性良好，这与固定化聚合物固定相的预期一致。
