A simple hand-held magnet array for efficient and reproducible SABRE hyperpolarisation using manual sample shaking.

Peter M Richardson,Andrew J Parrott,Meghan E Halse,Simon B Duckett,Scott Jackson,Alison Nordon

doi:10.1002/mrc.4687

Peter M Richardson, Andrew J Parrott + Show 4 more

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https://doi.org/10.1002/mrc.4687

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Abstract

Signal amplification by reversible exchange (SABRE) is a hyperpolarisation technique that catalytically transfers nuclear polarisation from parahydrogen, the singlet nuclear isomer of H2, to a substrate in solution. The SABRE exchange reaction is carried out in a polarisation transfer field (PTF) of tens of gauss before transfer to a stronger magnetic field for nuclear magnetic resonance (NMR) detection. In the simplest implementation, polarisation transfer is achieved by shaking the sample in the stray field of a superconducting NMR magnet. Although convenient, this method suffers from limited reproducibility and cannot be used with NMR spectrometers that do not have appreciable stray fields, such as benchtop instruments. Here, we use a simple hand‐held permanent magnet array to provide the necessary PTF during sample shaking. We find that the use of this array provides a 25% increase in SABRE enhancement over the stray field approach, while also providing improved reproducibility. Arrays with a range of PTFs were tested, and the PTF‐dependent SABRE enhancements were found to be in excellent agreement with comparable experiments carried out using an automated flow system where an electromagnet is used to generate the PTF. We anticipate that this approach will improve the efficiency and reproducibility of SABRE experiments carried out using manual shaking and will be particularly useful for benchtop NMR, where a suitable stray field is not readily accessible. The ability to construct arrays with a range of PTFs will also enable the rapid optimisation of SABRE enhancement as function of PTF for new substrate and catalyst systems.

Highlights

Of the range of available hyperpolarisation techniques, we focus here on the signal amplification by reversible exchange (SABRE) approach, which is a catalytic method for transferring spin order from the nuclear singlet isomer of H2, parahydrogen (p‐H2), to nuclear magnetic resonance (NMR)‐active nuclei in a molecule of interest.[7]
We have presented a method for designing and implementing a hand‐held magnet array for use in SABRE hyperpolarisation experiments using a manual shaking approach
We have demonstrated that the hand‐held arrays provide improved reproducibility and SABRE efficiency over the stray field approach

Summary

Introduction

The use of hyperpolarisation for sensitivity enhancement through the generation of non‐equilibrium nuclear spin populations is an increasingly important area of development in magnetic resonance due to its potential to enable new applications in solid‐ and liquid‐state nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI).[1,2,3,4,5,6] Of the range of available hyperpolarisation techniques, we focus here on the signal amplification by reversible exchange (SABRE) approach, which is a catalytic method for transferring spin order from the nuclear singlet isomer of H2, parahydrogen (p‐H2), to NMR‐active nuclei in a molecule of interest.[7]. The level of polarisation that can be achieved (as much as 50% for 1H nuclei[8]) is independent of the NMR or MRI detection field. This means that SABRE is a attractive method for sensitivity enhancement of low‐cost and portable benchtop NMR and MRI devices where the detection fields are typically limited to 1–2 T.[9] the implementation of a SABRE experiment is relatively straight‐forward, fast, and not technologically demanding compared to other hyperpolarisation methods such as dissolution dynamic nuclear polarisation.[4]

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