In the present study, we characterize a famous Pirkle-type enantioselective stationary phase ((R,R)-Whelk-O1 from Regis Technologies) and an equivalent enantiomeric phase (ReproSil Chiral-NR from Dr. Maisch) in supercritical fluid chromatography (SFC) with carbon dioxide – methanol (90:10 v/v) mobile phase. First, the interactions contributing to retention are evaluated with a modified version of the solvation parameter model, comprising five Abraham descriptors (E, S, A, B, V), two additional descriptors to take account of molecular shape (flexibility F and globularity G), and two additional descriptors to take account of interactions with ionizable species (D⁻ and D⁺). Linear solvation energy relationships (LSER) are established based on the retention of 212 achiral analytes. As expected, π-π interactions are the most significant to explain retention, while dipole-dipole, hydrogen bonding and ionic interactions with cationic species are of secondary importance. Secondly, the contributions of interactions to enantioseparations are discussed, based on the analysis of 79 racemates. Discriminant analyses (DA) were computed to gain some insight on retention mechanisms. The set of racemates is first divided between racemates eluted earlier than expected based on the LSER models, and those eluted later than expected. Small spherical molecules are more retained than expected, as they may better fit inside the cleft of the chiral selector. They are also most frequently resolved, probably for the same reason. Among the molecules that are less retained than expected, which are rather large and/or non-spherical, other features are favourable to enantiorecognition: π-electrons, dipoles and electron-donating properties. Contrary to the observations on other sorts of chiral selectors, flexibility was found to have no contribution on the enantiorecognition process.

在本研究中，我们在超临界流体色谱（SFC）中表征了著名的Pirkle型对映选择性固定相（Regis Technologies的（R，R）-Whelk-O1）和等效对映体相（Maisch博士的ReproSil Chiral-NR）。 ）与二氧化碳-甲醇（90:10 v / v）流动相。首先，使用改良版本的溶剂化参数模型评估有助于保留的相互作用，该模型包含五个亚伯拉罕描述子（E，S，A，B，V），两个附加描述子考虑分子形状（柔性F和球形度G） ），以及两个附加的描述符，以考虑与电离物质（d相互作用^-和d ⁺）。线性溶剂化能量关系（LSER）是基于212种非手性分析物的保留量而建立的。不出所料，π-π相互作用对解释保留最重要，而偶极-偶极，氢键和与阳离子物质的离子相互作用则次要。其次，基于对79位外消旋体的分析，讨论了相互作用对对映体分离的贡献。计算判别分析（DA）可以对保留机制有所了解。外消旋体的集合首先根据LSER模型在早于预期洗脱的外消旋体和晚于预期洗脱的外消旋体之间进行划分。球形小分子比预期的保留更多，因为它们可以更好地适合手性选择剂的缝隙。它们也是最常见的解决方法，可能是出于相同的原因。在保留程度低于预期的分子中，它们相当大和/或非球形，在其他特征中有利于对映体识别：π电子，偶极子和给电子性。与其他类型手性选择剂的观察结果相反，发现灵活性对对映体识别过程没有贡献。