高等学校化学学报

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固体核磁共振Multiple-CP定量技术的参数优化与应用研究

张志兰, 王宁, 唐丹丹, 舒婕(), 李晓虹()   

  1. 苏州大学材料与化学化工学部, 分析测试中心, 苏州 215123
  • 收稿日期:2020-09-22
  • 通讯作者: 舒婕 E-mail:shujie@suda.edu.cn;lxh83@suda.edu.cn
  • 作者简介:李晓虹, 女, 博士, 副教授, 主要从事液体核磁共振方法在高分子材料中的应用研究. E-mail: lxh83@suda.edu.cn
  • 基金资助:
    国家自然科学基金(21673148)

Experimental Set-up and Application Research of Solid-State Nuclear Magnetic Resonance Multiple-CP Technique

ZHANG Zhilan, WANG Ning, TANG Dandan, SHU Jie(), LI Xiaohong()   

  1. College of Chemistry,Chemical Engineering and Materials Science,Testing and Analysis Center,Soochow University,Suzhou 215123,China
  • Received:2020-09-22
  • Contact: SHU Jie E-mail:shujie@suda.edu.cn;lxh83@suda.edu.cn
  • Supported by:
    ? Supported by the National Natural Science Foundation of China(21673148)

摘要:

固体核磁共振Multiple-CP定量技术可实现对不同体系、 不同定量信息的检测. 然而, Multiple-CP对样品属性的宽容度较低, 其中有关样品属性的核磁共振参数包括氢的自旋晶格弛豫时间(T1,H)、 交叉弛豫时 间(TCH)和自旋锁定场下氢的自旋晶格弛豫时间(T1ρ?H)等. 因而需要系统地掌握Multiple-CP各种实验参数与样品上述特性参数之间的关系, 从而确定Multiple-CP技术可适用的体系范围以及最优的实验参数范围. 基于此, 首先以L-丙氨酸为模型样品, 探讨在Multiple-CP实验中弛豫恢复时间(td)、 交叉极化接触时间(tp)和交叉极化次数(n) 3种实验参数对分子中基团比例测量结果的影响规律. 并以L-缬氨酸、 L-丙氨酸/L-缬氨酸的混合物为模型样品, 探讨样品特性参数的差异性对Multiple-CP实验参数范围的影响. 实验结果表明, tpTCH?T1ρ?H的影响较大. 对于纯净物或均相体系, TCH是影响tp参数设置的关键. 依据实验数据发现, 当样品中各基团TCH差异度小于8%时, 实验对tp的宽容度较高; 对于混合物体系, 需同时考虑混合物中组分?T1ρ?H?差异度的影响. 当组分?T1ρ?H?差异度为32%、 各基团TCH差异度为21%时, Multiple-CP对tp的宽容度高, 可在较宽的参数范围内实现定量检测. 而当TCH差异度较大时, 获取定量结果时tp的参数范围较小, 实验条件较苛刻. Multiple-CP定量方法更适用于TCH?T1ρ?H?差异度较小的样品体系的定量研究. 通过研究样品TCH?T1ρ?H?对实验参数的影响, 总结了Multiple-CP方法所适用的样品体系特征, 为使用Multiple-CP进行定量检测提供可参考的参数设置方案.

关键词: 固体核磁共振, 定量, 多次交叉极化, 实验参数, 交叉极化接触时间

Abstract:

The quantitative solid-state nuclear magnetic resonance(NMR) multiple-cross polarization(CP) technique attracts enormous interest of the material researchers. With proper setting of experimental parameters, Multiple-CP is capable to determine the molecular chemical structure, multi-phase composition and the component contents of blends. However, the accuracy of the testing results is sensitive to the experimental parameters which are tuned by the system parameters of the measuring samples. To gain the accurate results with high efficiency, it is necessary to reveal the influence behavior of the system parameters on experimental parameters. In this work, L-alanine, L-valine and their mixture were chosen as the model samples. Firstly, system parameters of spin-lattice relaxation time of 1H(T1,H), cross relaxation time(TCH) and spin?lattice relaxation time of 1H in the spin?locking field(T1ρ?H?) were measured. Meanwhile, the accuracy of Multiple-CP results was evaluated with the variation of three experimental parameters, including relaxation recovery time(td), cross-polarization contact time(tp), and cross-polarization times(n). By comparing the data of different 13C groups, it is revealed that the setting of tp is essential to the result accuracy, which is tuned by TCH and ?T1ρ?H? of the system. Moreover, the values of the parameter difference between the molecular groups or blended components also affects the Multiple-CP results. Therefore, Multiple-CP is recommended to study the systems with similar TCH and ?T1ρ?H? values. For the blends or mixtures, the identical unit of each component is suggested chosen for determining the contents.

Key words: Solid-state nuclear magnetic resonance(SSNMR), Qualification, Multiple-cross polarization, Experimental parameter, Cross-polarization contact time

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