We investigated the dual retention mechanism in thin-layer chromatography taking place on three stationary phases of different polarity (C-18, plain silica gel and DIOL) and using binary mobile phases composed of acetonitrile as the main component and water, or methanol as a modifier. As the test analytes, we selected a set of 12 compounds of pharmaceutical importance and considerably different chemical structure, i.e. the imidazoline and serotonin receptor ligands, and their related compounds. Retention of each analyte in each investigated chromatographic system was determined in a wide enough range of the mobile phase composition, with volume fraction of the mobile phase modifier ranging from 0.10 to 0.90. Calculation of the exact turning point values as a proof of occurrence of the reversed-phase hydrophilic interaction chromatography (HILIC/RP) retention mechanism was based on the multimodal retention model. The dual retention mode was described with the use of the volume fraction of the mobile phase modifier, the total polarity and the total solubility models. For the DIOL, C-18 and silica gel stationary phase, the dual (HILIC/RP) retention mechanism was confirmed. In the case of the DIOL stationary phase and acetonitrile/methanol mobile phase, the observed retention mechanism was more complicated than the dual HILIC/RP one.

中文翻译：

---

薄层色谱中的混合模式亲水相互作用/反相保留机制

我们研究了薄层色谱法中的双重保留机制，发生在三种不同极性的固定相（C-18、普通硅胶和 DIOL）上，并使用由乙腈作为主要成分和水或甲醇作为一种二元流动相组成。修饰符。作为测试分析物，我们选择了一组 12 种具有药学重要性和显着不同化学结构的化合物，即咪唑啉和血清素受体配体，以及它们的相关化合物。每个研究的色谱系统中每种分析物的保留在足够宽的流动相组成范围内确定，流动相改性剂的体积分数范围为 0.10 至 0.90。作为反相亲水相互作用色谱 (HILIC/RP) 保留机制发生的证据的确切转折点值的计算基于多峰保留模型。使用流动相改性剂的体积分数、总极性和总溶解度模型描述了双重保留模式。对于 DIOL、C-18 和硅胶固定相，确认了双重 (HILIC/RP) 保留机制。在 DIOL 固定相和乙腈/甲醇流动相的情况下，观察到的保留机制比双 HILIC/RP 的保留机制更复杂。对于 DIOL、C-18 和硅胶固定相，确认了双重 (HILIC/RP) 保留机制。在 DIOL 固定相和乙腈/甲醇流动相的情况下，观察到的保留机制比双 HILIC/RP 的保留机制更复杂。对于 DIOL、C-18 和硅胶固定相，确认了双重 (HILIC/RP) 保留机制。在 DIOL 固定相和乙腈/甲醇流动相的情况下，观察到的保留机制比双 HILIC/RP 的保留机制更复杂。