Effect of salts on retention in hydrophilic interaction chromatography
Effect of salts on retention in hydrophilic interaction chromatography
复制标题
盐对亲水相互作用色谱保留率的影响
DOI：
10.1016/j.chroma.2018.01.038
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发表时间：
2018-02-23
影响因子：
4.1
通讯作者：
Alpert, Andrew J.
中科院分区：
文献类型：
--
作者：
Alpert, Andrew J.
人们普遍认为盐通过扩大固定相表面固定水层的体积来促进亲水相互作用色谱 (HILIC) 中溶质的保留。迄今为止，所有关于这一前提的研究都存在缺陷或局限性，导致问题悬而未决。本研究探讨了盐类型和浓度的影响。使用四种三乙铵盐（从亲液硫酸盐到离液高氯酸盐）研究了阴离子的影响，pH 值分别为 3 和 6。浓度范围为 5-120 mM。除胞嘧啶和胞苷外，所有分析物均呈中性，在 pH 3 时带 (+) 电荷。硫酸盐显着促进胞嘧啶、胞苷和间苯三酚的保留。在高硫酸盐水平下，胞嘧啶和胞苷的保留再次减少，可能是由于“盐析”效应。对于高氯酸根阴离子，胞嘧啶的保留随着盐浓度的增加而稳定下降，而其他标准品的保留增加或保持不变。通过比较在相同位置含有磷酸丝氨酸或天冬氨酸的胰蛋白酶肽的保留来检查阳离子的影响。甲基膦酸盐在pH 2.5 下使用。阳离子的水合数越高，两种肽之间的选择性越好。使用镁盐获得最好的分离效果，使用四甲基铵盐获得最差的分离效果。高度水合的阳离子所贡献的保留超过了由于静电吸引而产生的保留。这些结果表明，水合良好的反离子有助于促进带电溶质分配到 HILIC 中的固定水层中，而水合不良的反离子则具有相反的作用。对中性溶质的影响较小；保留时间保持不变或随着任何盐浓度的增加而适度增加。 (C) 2018 作者。由 Elsevier B.V. 出版
There is a widespread belief that salts promote retention of solutes in hydrophilic interaction chromatography (HILIC) by expanding the volume of the immobilized layer of water on the surface of the stationary phase. To date, all studies of this premise have had flaws or limitations that left the question open. This study explored the effects of salt type and concentration.The effect of the anion was studied with four triethylammonium salts, ranging from the kosmotropic sulfate to the chaotropic perchlorate, at pH values of both 3 and 6. Concentrations ranged from 5-120 mM. All analytes were neutral except for cytosine and cytidine, which had (+) charge at pH 3. Sulfate markedly promoted retention of cytosine, cytidine and phloroglucinol. At high sulfate levels retention of cytosine and cytidine decreased again, presumably due to a "salting-out" effect. With perchlorate anion, retention of cytosine decreased steadily as salt concentration increased, while retention of other standards increased or was unchanged.The effect of the cation was examined by comparing the retention of a tryptic peptide containing either phosphoserine or aspartic acid at the same position. Salts of methylphosphonic acid were used at pH 2.5. The higher the hydration number of the cation, the better the selectivity between the two peptides. The best separation was obtained with the magnesium salt and the worst with the tetramethylammonium salt. The retention contributed by a highly hydrated cation exceeded retention due to electrostatic attraction.These results demonstrate that counterions that are well hydrated serve to promote partitioning of charged solutes into the immobilized aqueous layer in HILIC, while poorly hydrated counterions have the opposite effect. Effects on neutral solutes were more modest; retention times remained unchanged or increased modestly with an increase in concentration of any salt. (C) 2018 The Author(s). Published by Elsevier B.V.