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Effect of the combined use of γ-cyclodextrin and a chiral ionic liquid on the enantiomeric separation of homocysteine by capillary electrophoresis
Journal of Chromatography A ( IF 4.1 ) Pub Date : 2018-07-05 , DOI: 10.1016/j.chroma.2018.07.023
Maider Greño , María Luisa Marina , María Castro-Puyana

The enantioseparation of the non-protein amino acid homocysteine by CE was investigated in this article using eleven neutral CDs and five chiral ionic liquids as chiral selectors. Using a previous derivatization step with FMOC and the subsequent separation under neutral conditions, homocysteine enantiomers were only separated when γ-CD or (R)-N,N,N-trimethyl-2-aminobutanol-bis(trifluoromethane-sulfon)imidate (EtCholNTf2) were employed as sole chiral selectors in the separation buffer. On the one hand, γ-CD gave rise to the enantiomeric separation in 10 min with a resolution value of 1.9, whereas EtCholNTf2 let to obtain a resolution value of 1.4 in more than 50 min. Then, the evaluation of the combined use of both selectors was also carried out, resulting in a considerable increase in the Rs. The best enantioseparation for homocysteine was obtained when 10 mM EtCholNTf2 was added to 50 mM phosphate buffer (pH 7.0) containing 2 mM γ-CD. In an attempt to discriminate specific chiral cation effect from the salt effect, the influence of adding LiNTf2 to the separation medium was also evaluated, resulting in lower resolution values for homocysteine when compared to those achieved with the addition of EtCholNTf2, indicating a synergistic effect between EtCholNTf2 and γ-CD. Interestingly, the enantiomer migration order changed depending on the use of a single chiral selector or dual systems. When EtCholNTf2 or γ-CD were employed as sole chiral selectors, D-enantiomer was the first-migrating enantiomer. However, an inversion in the migration order was observed when both selectors were combined in a dual system being the L-enantiomer the first-migrating one.



中文翻译:

γ-环糊精与手性离子液体组合使用对毛细管电泳对高半胱氨酸对映体分离的影响

本文使用11种中性CD和5种手性离子液体作为手性选择剂,研究了CE对非蛋白质氨基酸高半胱氨酸的对映体分离。使用先前的FMOC衍生步骤并随后在中性条件下分离,仅当γ-CD或(R)-N,N,N-三甲基-2-氨基丁醇-双(三氟甲烷-磺)亚氨酸酯(EtCholNTf 2)被用作分离缓冲液中的唯一手性选择剂。一方面,γ-CD在10分钟内引起对映体分离,分离度为1.9,而EtCholNTf 2让我们在50分钟以上的时间内获得1.4的分辨率值。然后,还对两个选择器的组合使用进行了评估,从而导致Rs显着增加。将10 mM EtCholNTf 2添加到含有2 mMγ -CD的50 mM磷酸盐缓冲液(pH 7.0)中,可获得最佳的同型半胱氨酸对映体分离。在试图从盐效果判别特定的手性阳离子效果,加入LiNTf的影响2至分离介质也评价,从而对高半胱氨酸较低分辨率的值相比,这些通过添加EtCholNTf的实现时2,表明有协同EtCholNTf 2之间的作用和γ-CD。有趣的是,对映体的迁移顺序根据单个手性选择剂或双系统的使用而改变。当EtCholNTf 2或γ-CD被用作唯一的手性选择剂时,D-对映异构体是第一个迁移的对映异构体。然而,当两个选择器组合在双重系统中时,迁移顺序发生了反转,该双重系统是第一个迁移的L-对映体。

更新日期:2018-07-05
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