NMR for Mixture Analysis: Concentration-Ordered Spectroscopy

A novel approach, concentration-ordered NMR spectroscopy (CORDY), is being proposed based on the principle that the ratio of the NMR peak area to its associated number of spins is proportional to the concentration of the assigned compound. Besides, prior information of chemical shift distribution and line shape characteristics of different chemical groups is utilized to shrink the solution space. CORDY generates a pseudo-two-dimensional NMR spectrum with chemical shifts in one axis and concentrations in the other, resulting in both separation and quantitation of components in complex samples. The method was validated by application to three samplesa model mixture containing six amino acids, sugar-free Red Bull, and human urine. It was demonstrated that CORDY could successfully separate the components with up to 2 orders of magnitude in the concentration dimension for the samples used in the current study. In addition, a combination of CORDY and DOSY (CORDY-DOSY) has been found to be more efficient in resolving the molecules with similar concentrations or self-diffusion coefficients.本研究提出了一种新型方法——浓度排序核磁共振波谱法（concentration-ordered NMR spectroscopy, CORDY），其基于核磁共振（Nuclear Magnetic Resonance, NMR）峰面积与其关联自旋数之比与目标化合物浓度成正比这一原理。此外，该方法还利用不同化学基团的化学位移分布与谱线形状特征等先验信息来压缩解空间。CORDY可生成伪二维核磁共振谱，其中一个轴为化学位移，另一个轴为浓度，从而实现复杂样品中各组分的分离与定量。本研究通过三组样品对该方法进行了验证：包含六种氨基酸的模型混合物、无糖红牛以及人尿液。结果表明，在本研究所用的样品中，CORDY可在浓度维度上实现最高达2个数量级的组分分离。此外，研究还发现CORDY与扩散排序核磁共振波谱法（DOSY）联用（CORDY-DOSY）可更高效地分辨浓度或自扩散系数相近的分子。