一种混合模式反相强阳离子交换色谱固定相的制备及其保留机理的考察

Preparation and retention mechanism of a mixed-mode reversedphase/strong-cationic-exchange chromatographic packing

采用一种简单的"混合配体"方法将辛基和磺酸基键合到硅胶表面,制备了辛基-磺酸基共同键合硅胶(OSS)材料。通过元素分析和吸附容量检测对OSS材料进行表征,证明辛基和磺酸基已成功键合到硅胶表面上。将该OSS硅胶材料作为混合模式反相强阳离子交换(RP/SCX)色谱固定相,在反相液相色谱(RPLC)流动相条件下,采用几种碱性探针分子定量地考察了该固定相的混合模式RP/SCX保留机理。通过改变流动相中缓冲盐的浓度,考察了溶质保留因子和盐浓度的对数和倒数的关系,得到了几种碱性探针分子在该混合模式OSS固定相上的单点和两点保留机理的数学模型。对两种数学模型的方程进行了线性拟合,结果表明两点保留机理更加符合实验的结果。此外,根据混合模式两点保留机理的数学方程,可以得到单一的疏水或离子交换作用力对总保留的影响,对混合模式色谱的实际分离应用可提供有价值的参考。

A simple and efficient method has been proposed for the preparation of octyl-sulfonic co-bonded silica（OSS） packing by the method of ＂mixed ligand＂.The resulting OSS packing was characterized by elemental analysis and ion-exchange capacity to prove the successful immobilization of octyl and sulfonic groups on the surface of silica gel.Then the retention mechanism of several basic analytes on the developed OSS phases was evaluated under the conditions of reversed-phase liquid chromatography（RPLC） mobile phase.The results indicated that the OSS stationary phases demonstrated a mixed-mode reversed-phase/strong-cationic-exchange（RP/SCX） retention mechanism and ion-exchange interaction maybe dominate the retention of the basic analytes.By changing the salt concentration of mobile phase,the one-site and two-site mixed-mode retention models of the several basic analytes on the OSS phases were obtained by investigating the logarithm and reciprocal relationships of retention factor and salt concentration.On the basis of the linear fitting of the two mathematical equations of the retention models,the experimental results demonstrated that the two-site model was more suitable for the description of the retention mechanism of the basic analytes on the OSS phases.Furthermore,the individual RP or SCX contribution to total retention was obtained according to the mathematical equations of the two-site retention mechanism,which can provide some valuable guidance for the separation of complex samples.