Centre for Hyperpolarisation in Magnetic Resonance, Department of Chemistry, University of York, UK.
WestCHEM, Department of Pure and Applied Chemistry and CPACT, University of Strathclyde, Glasgow, UK.
Phys Chem Chem Phys. 2018 Nov 7;20(41):26362-26371. doi: 10.1039/c8cp05473h. Epub 2018 Oct 10.
para-Hydrogen (p-H) induced polarisation (PHIP) is an increasingly popular method for sensitivity enhancement in NMR spectroscopy. Its growing popularity is due in part to the introduction of the signal amplification by reversible exchange (SABRE) method that generates renewable hyperpolarisation in target analytes in seconds. A key benefit of PHIP and SABRE is that p-H can be relatively easily and cheaply produced, with costs increasing with the desired level of p-H purity. In this work, the efficiency of the SABRE polarisation transfer is explored by measuring the level of analyte hyperpolarisation as a function of the level of p-H enrichment. A linear relationship was found between p-H enrichment and analyte H hyperpolarisation for a range of molecules, polarisation transfer catalysts, NMR detection fields and for both the SABRE and SABRE-Relay transfer mechanisms over the range 29-99% p-H purity. The gradient of these linear relationships were related to a simple theoretical model to define an overall efficiency parameter, E, that quantifies the net fraction of the available p-H polarisation that is transferred to the target analyte. We find that the efficiency of SABRE is independent of the NMR detection field and exceeds E = 20% for methyl-4,6-d-nicotinate when using a previously optimised catalyst system. For the SABRE-Relay transfer mechanism, efficiencies of up to E = 1% were found for H polarisation of 1-propanol, when ammonia was used as the polarisation carrier.
反氢（p-H）诱导极化（PHIP）是一种在 NMR 光谱中提高灵敏度的越来越流行的方法。它的日益普及部分归因于信号放大可逆交换（SABRE）方法的引入，该方法可在几秒钟内为目标分析物产生可再生的超极化。PHIP 和 SABRE 的一个关键优势是 p-H 相对容易且廉价地产生，成本随所需的 p-H 纯度水平而增加。在这项工作中，通过测量分析物超极化的水平作为 p-H 富集水平的函数，来探索 SABRE 极化转移的效率。在 p-H 纯度为 29-99%的范围内，发现一系列分子、极化转移催化剂、NMR 检测场以及 SABRE 和 SABRE-Relay 转移机制之间存在 p-H 富集与分析物 H 超极化之间的线性关系。这些线性关系的梯度与一个简单的理论模型相关联，该模型定义了一个整体效率参数 E，该参数量化了可用于转移到目标分析物的可用 p-H 极化的净分数。我们发现，SABRE 的效率与 NMR 检测场无关，并且当使用先前优化的催化剂系统时，对于甲基-4,6-d-烟酸盐，E 超过 20%。对于 SABRE-Relay 转移机制，当使用氨作为极化载体时，在 1-丙醇的 H 极化中发现效率高达 E = 1%。
