Dipartimento di Chimica e Tecnologia del Farmaco, Università degli Studi di Perugia, Perugia, Italy.
J Chromatogr A. 2012 Dec 21;1269:316-24. doi: 10.1016/j.chroma.2012.08.018. Epub 2012 Aug 16.
With the use of a chiral ligand-exchange chromatography (CLEC) system operating with the O-benzyl-(S)-serine [(S)-OBS] [1,2] as the chiral mobile phase (CMP) additive to the eluent, the effect of the copper(II) anion type on retention (k) and separation (α) factors was evaluated, by rationally changing the following experimental conditions: salt concentration and temperature. The CLEC-CMP analysis was carried out on ten amino acidic racemates and with nine different cupric salts. While the group of analytes comprised both aliphatic (leucine, isoleucine, nor-leucine, proline, valine, nor-valine, and α-methyl-valine) and aromatic (1-aminoindan-1,5-dicarboxylic acid, phenylglycine, and tyrosine) species, representative organic (formate, methanesulfonate, and trifluoroacetate) and inorganic (bromide, chloride, fluoride, nitrate, perchlorate, and sulfate) Cu(II) salts were selected as the metal source into the eluent. This route of investigation was pursued with the aim of identifying analogies among the employed Cu(II) salts, by observing the variation profile of the selected chromatographic parameters, upon a change of the above experimental conditions. All the data were collected and analyzed through a statistical approach (PCA and k-means clustering) that revealed the presence of two behavioral classes of cupric salts, sharing the same variation profile for k and α values. Interestingly, this clustering can be explained in terms of ESP (electrostatic surface potential) balance (ESP(bal)) values, obtained by an ab initio calculation operated on the cupric salts. The results of this appraisal could aid the rational choice of the most suitable eluent system, to succeed in the enantioseparation of difficult-to-resolve compounds, along with the eventual scale-up to a semi-preparative level.
采用手性配体交换色谱（CLEC）系统，以 O-苄基-（S）-丝氨酸[（S）-OBS][1,2]作为手性流动相（CMP）添加剂到洗脱液中，通过合理改变以下实验条件：盐浓度和温度，评估铜（II）阴离子类型对保留（k）和分离（α）因子的影响。CLEC-CMP 分析在十种氨基酸对映体上进行，并使用九种不同的铜盐。虽然分析物组包括脂肪族（亮氨酸、异亮氨酸、正亮氨酸、脯氨酸、缬氨酸、正缬氨酸和α-甲基缬氨酸）和芳香族（1-氨基茚满-1,5-二羧酸、苯甘氨酸和酪氨酸）两种，代表性的有机（甲酸盐、甲磺酸盐和三氟乙酸盐）和无机（溴化物、氯化物、氟化物、硝酸盐、高氯酸盐和硫酸盐）Cu（II）盐被选为金属源进入洗脱液。进行这种研究路线的目的是通过观察所选色谱参数的变化趋势，在改变上述实验条件时，确定所使用的 Cu（II）盐之间的相似性。所有数据均通过统计方法（PCA 和 k-means 聚类）进行收集和分析，该方法揭示了存在两种行为类别的铜盐，它们的 k 和α值具有相同的变化趋势。有趣的是，这种聚类可以根据静电表面电势（ESP）平衡（ESP（bal））值来解释，这些值是通过对手性铜盐进行从头计算获得的。该评估的结果可以帮助合理选择最合适的洗脱液系统，以成功分离难以分离的化合物，并最终扩展到半制备规模。
