Periodic Artifact Suppression for Pure Shift NMR Spectroscopy

Pure shift techniques, as one of the rapidly developing frontiers in nuclear magnetic resonance (NMR) fields, can significantly enhance the resolution of NMR spectrum with a removal of splittings induced by scalar couplings. However, periodic artifacts due to residual scalar couplings during acquisition arise on all direct pure shift spectra, causing severe problems in analysis of complicated samples. Herein, we construct a signal model for the pure shift data and discuss the mechanism of periodic artifacts. Then, based on constraints on the low-rank property of pure shift NMR data, a subsequent artifact-suppression method is proposed to reconstruct a clean pure shift spectrum. With the proposed method, clean 1H pure shift spectrum can be obtained from only one experiment, greatly accelerating the experiment time while remaining the accuracy of the quantitative measurement. Experiments on a synthesis NMR signal, a complex sample of quinine with pseudo 2-D acquisition, and a medicine sample of azithromycin with 1-D acquisition are carried out to evaluate the feasibility and universality of the proposed method for different experimental techniques. Both the theoretical analysis and experimental results demonstrate the effectiveness of the proposed method for periodic artifacts suppression on complex samples and its potential for practical applications.

纯位移技术作为核磁共振（NMR）领域中快速发展的前沿技术之一，能够通过去除由标量耦合引起的裂分显著提高NMR谱图的分辨率。然而，在采集过程中由于残余标量耦合产生的周期性伪影出现在所有直接纯位移谱图上，这给复杂样品的分析带来了严重问题。在此，我们构建了一个纯位移数据的信号模型，并讨论了周期性伪影的产生机制。然后，基于对纯位移NMR数据低秩特性的约束，提出了一种后续的伪影抑制方法来重建干净的纯位移谱图。利用所提出的方法，仅通过一次实验就可以获得干净的1H纯位移谱图，在保持定量测量准确性的同时大大缩短了实验时间。对合成的NMR信号、采用伪二维采集的奎宁复杂样品以及采用一维采集的阿奇霉素药物样品进行了实验，以评估所提出方法对不同实验技术的可行性和通用性。理论分析和实验结果都证明了所提出方法对复杂样品周期性伪影抑制的有效性以及其在实际应用中的潜力。