School of Chemical Engineering, Northwest University, Xi'an, Shaanxi Province 710069, PR China.
School of Chemical Engineering, Northwest University, Xi'an, Shaanxi Province 710069, PR China.
J Chromatogr A. 2020 Jun 7;1620:460978. doi: 10.1016/j.chroma.2020.460978. Epub 2020 Feb 14.
To explore the retention and separation of stevioside polar compounds on a sulfonic acid-functionalized cation exchange column, the effects of different organic solvent-water mobile phases on the retention behavior of polar rebaudioside A (RA) and its analogues on the column were investigated over a wide range of organic solvent contents. The obtained U-shape curves hinted that the retention of the compounds on the same column transitioned from a reversed-phase liquid chromatography (RPLC) mode to a hydrophilic interaction liquid chromatography (HILIC) mode when the water-rich state in the mobile phases changed to an organic solvent-rich state. Under the RPLC mode, no separation of RA from its analogues was observed. The HILIC mode was beneficial to the retention and separation of RA and its analogues. Compared with polar protic solvents, aprotic solvents were more conducive to the retention and separation of the polar compounds based on the HILIC mode in organic solvent-rich mobile phases. Three models were used to evaluate and discuss the HILIC retention and separation of the compounds on the column. In the aprotic solvent-rich mobile phase, the HILIC retention of RA and its analogues was effectively described by a mixed-mode model; in the polar proton solvent-rich mobile phase, the retention of analytes was best described by an linear solvation strength (LSS) model. The content and composition of the organic solvent in the mobile phase were determined to be important influencing factors that regulated the retention time for the RA and its analogues, and even the separation mechanism for HILIC. The present work provides a theoretical basis for guiding one to prepare high-purity RA from its analogues by predicting the retention time.
为了探索甜菊苷极性化合物在磺酸基功能化阳离子交换柱上的保留和分离情况，考察了不同有机-水流动相组成对极性甜菊醇 A（RA）及其类似物在该柱上保留行为的影响。在较宽的有机相含量范围内，获得的 U 型曲线表明，当流动相中的水相状态向有机相状态转变时，化合物在同一柱上的保留从反相液相色谱（RPLC）模式转变为亲水相互作用液相色谱（HILIC）模式。在 RPLC 模式下，未观察到 RA 与其类似物的分离。HILIC 模式有利于 RA 及其类似物的保留和分离。与极性质子溶剂相比，在富含有机溶剂的流动相中，非质子溶剂更有利于基于 HILIC 模式保留和分离极性化合物。采用三种模型对化合物在柱上的 HILIC 保留和分离进行了评价和讨论。在非质子溶剂丰富的流动相中，RA 及其类似物的 HILIC 保留可以用混合模式模型有效描述；在极性质子溶剂丰富的流动相中，线性溶剂化强度（LSS）模型可以更好地描述分析物的保留。流动相中的有机溶剂含量和组成被确定为调节 RA 和其类似物保留时间的重要影响因素，甚至是 HILIC 的分离机制。本工作为通过预测保留时间来指导从类似物中制备高纯度 RA 提供了理论依据。
