Polyacrylamide grafted on multi-walled carbon nanotubes for open-tubular capillary electrochromatography: Comparison with silica hydride and polyacrylate phase matrices
Polyacrylamide grafted on multi-walled carbon nanotubes for open-tubular capillary electrochromatography: Comparison with silica hydride and polyacrylate phase matrices
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DOI：
10.1002/elps.201000339
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发表时间：
2010-12-01
期刊：
影响因子：
2.9
通讯作者：
Hsieh, Kai-Hsin
中科院分区：
文献类型：
--
作者：
Chen, Jian-Lian;Hsieh, Kai-Hsin
利用MWNT结构中环戊二烯基环中丰富的双键，通过甲基丙烯酰胺（MAA）、双丙烯酰胺交联剂和羧化多壁碳纳米管（多壁碳纳米管；MWNT）在硅烷化毛细管上的原位聚合制备了一种新型纳米粒子结合的聚合物固定相。通过 SEM、ATR-IR 和改变运行缓冲液中 ACN 的 pH、浓度和体积比的 EOF 测量来表征合成步骤之间的每个中间毛细管。所得的 EOF 曲线与其他两个具有不同相基质、二氧化硅和聚甲基丙烯酸丁酯 (BMA) 相的毛细管的 EOF 曲线相当。凭借亲水性聚丙烯酰胺网络上 MWNT 的复杂功能，MAA-CNT 毛细管能够使用开管 CEC 分离具有各种极性和解离特性的不同样品。除了优化 CEC 条件外，还根据速度和保留因子分析样品的迁移时间，以评估电泳和色谱对 CEC 机制的贡献。苯甲酸的迁移速率由各种酚离子的电泳迁移率决定，而酚醛和酮还受到色谱相互作用的影响，例如p-p、静电效应、氢键和疏水相互作用。黄酮类化合物（多酚类）的保留因子比简单酚类的保留因子更大，但小于从疏水性 BMA-CNT 柱获得的保留因子。通过电泳或色谱法在 MAA-CNT 毛细管中实现了四环素阳离子形式的完全分离，但在 BMA-CNT 和二氧化硅氢化物-CNT 毛细管中则不然。
A new nanoparticle-bound polymer stationary phase was prepared by in situ polymerization of methacrylamide (MAA), bis-acrylamide crosslinker, and carboxylated multi-walled carbon nanotubes (multi-walled CNTs; MWNTs), using the abundant double bonds in the cyclopentadienyl rings in MWNT structure, on a silanized capillary. Each intermediate capillary between the synthesis steps was characterized by SEM, by ATR-IR, and by EOF measurements varying the pH, concentration, and volumetric ratios of ACN in running buffers. The resulting EOF profile was comparable to those of two other capillaries with different phase matrices, silica hydride and polybutyl methacrylate (BMA) phases. With the complex functionality of MWNTs on the hydrophilic polyacrylamide network, the MAA-CNT capillary was capable of separating diverse samples with a wide range of polarity and dissociation properties using open-tubular CEC. Besides optimizing CEC conditions, the migration times of samples were analyzed with respect to velocity and retention factors to evaluate electrophoretic and chromatographic contributions to the CEC mechanism. The migration rates of benzoic acids were determined by the electrophoretic mobilities of the various phenolate ions, while phenolic aldehydes and ketones were additionally influenced by chromatographic interactions, such as p-p, electrostatic effects, hydrogen bonding, and hydrophobic interactions. The retention factors were greater for flavonoids, which are polyphenolic, than for simple phenols, but were smaller than those obtained from the hydrophobic BMA-CNT column. A complete well-resolved separation of the cationic forms of tetracyclines was acheived either by electrophoresis or by chromatography in the MAA-CNT capillary, but not in the BMA-CNT and silica hydride-CNT capillaries.