Centre for Hyperpolarisation in Magnetic Resonance, Department of Chemistry, University of York, UK.
Analyst. 2018 Jul 9;143(14):3442-3450. doi: 10.1039/c8an00596f.
Benchtop NMR spectrometers operating with low magnetic fields of 1-2 T at sub-ppm resolution show great promise as analytical platforms that can be used outside the traditional laboratory environment for industrial process monitoring. One current limitation that reduces the uptake of benchtop NMR is associated with the detection fields' reduced sensitivity. Here we demonstrate how para-hydrogen (p-H2) based signal amplification by reversible exchange (SABRE), a simple to achieve hyperpolarization technique, enhances agent detectability within the environment of a benchtop (1 T) NMR spectrometer so that informative 1H and 13C NMR spectra can be readily recorded for low-concentration analytes. SABRE-derived 1H NMR signal enhancements of up to 17 000-fold, corresponding to 1H polarization levels of P = 5.9%, were achieved for 26 mM pyridine in d4-methanol in a matter of seconds. Comparable enhancement levels can be achieved in both deuterated and protio solvents but now the SABRE-enhanced analyte signals dominate due to the comparatively weak thermally-polarized solvent response. The SABRE approach also enables the acquisition of 13C NMR spectra of analytes at natural isotopic abundance in a single scan as evidenced by hyperpolarized 13C NMR spectra of tens of millimolar concentrations of 4-methylpyridine. Now the associated signal enhancement factors are up to 45 500 fold (P = 4.0%) and achieved in just 15 s. Integration of an automated SABRE polarization system with the benchtop NMR spectrometer framework produces renewable and reproducible NMR signal enhancements that can be exploited for the collection of multi-dimensional NMR spectra, exemplified here by a SABRE-enhanced 2D COSY NMR spectrum.
台式 NMR 光谱仪在 1-2 T 的低磁场下运行，具有亚 ppm 的分辨率，作为分析平台具有很大的应用潜力，可在传统实验室环境之外用于工业过程监测。目前，一个限制其应用的因素是检测场的灵敏度降低。在这里，我们展示了如何利用 para-hydrogen (p-H2) 基于信号放大的可逆交换 (SABRE) 技术，这种简单的极化技术可以提高台式 (1 T) NMR 光谱仪环境中试剂的检测灵敏度，从而可以轻松地记录低浓度分析物的信息丰富的 1H 和 13C NMR 谱。SABRE 衍生的 1H NMR 信号增强高达 17000 倍，对应于 1H 极化水平 P = 5.9%，对于 d4-甲醇中的 26 mM 吡啶，可在数秒内实现。在氘代和质子溶剂中都可以达到类似的增强水平，但现在由于热极化溶剂响应较弱，SABRE 增强的分析物信号占主导地位。SABRE 方法还可以实现天然丰度分析物的 13C NMR 谱的单次扫描采集，这一点可以从数十毫摩尔浓度的 4-甲基吡啶的超极化 13C NMR 谱中得到证明。现在，相关的信号增强因子高达 45500 倍（P = 4.0%），并且可以在 15 秒内实现。将自动化的 SABRE 极化系统与台式 NMR 光谱仪框架集成，可以产生可再生和可重复的 NMR 信号增强，可用于多维 NMR 谱的采集，这里通过 SABRE 增强的 2D COSY NMR 谱进行了举例说明。
