Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory, 1/3, GSP-1, Moscow, 119991, Russia.
Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory, 1/3, GSP-1, Moscow, 119991, Russia.
J Chromatogr A. 2019 Jul 5;1596:117-123. doi: 10.1016/j.chroma.2019.03.006. Epub 2019 Mar 7.
Four covalently-bonded hyperbranched anion exchangers based on poly(styrene-divinylbenzene) (PS-DVB) substrate with different structure of the functional layer were prepared using mono- and dianionic amino acids such as glycine, β-alanine, aspartic acid, and glutamic acid in the internal part of the functional layer. Selectivity of all anion exchangers toward weakly retained organic acids was investigated at different temperatures in order to evaluate the effect of the number of carboxylic groups in the functional layer and its hydrophilicity on the separation. It was found that dianionic amino acids used in the first modification cycle of hyperbranching provide the best resolution for mono- and divalent organic acids, which makes the number of carboxylic groups in the structure of amino acid a key factor in the separation of such analytes with covalently-bonded hyperbranched anion exchangers, while the role of amino acid hydrophilicity is not that significant. Stationary phases prepared using aspartic and glutamic acids provided baseline resolution for quinic, glycolic, acetic, lactic, formic, and galacturonic acids, which are not resolved to baseline with modern commercially available anion exchangers; the increase of temperature was found to be favorable for improving the resolution even further.
四种基于聚苯乙烯-二乙烯基苯（PS-DVB）基质的共价键合超支化阴离子交换剂，具有不同功能层结构，在功能层内部使用单阴离子和双阴离子氨基酸，如甘氨酸、β-丙氨酸、天冬氨酸和谷氨酸进行制备。在不同温度下，研究了所有阴离子交换剂对弱保留有机酸的选择性，以评估功能层中羧酸基团的数量及其亲水性对分离的影响。结果发现，在超支化的第一个修饰循环中使用的双阴离子氨基酸为单价和二价有机酸提供了最佳的分辨率，这使得氨基酸结构中的羧酸基团数量成为用共价键合超支化阴离子交换剂分离此类分析物的关键因素，而氨基酸亲水性的作用则不那么重要。使用天冬氨酸和谷氨酸制备的固定相可对奎尼酸、乙醇酸、乙酸、乳酸、甲酸和半乳糖醛酸实现基线分离，而现代市售的阴离子交换剂则无法实现基线分离；发现增加温度有利于进一步提高分辨率。
