Continuous hyperpolarization with parahydrogen in a membrane reactor

Hyperpolarization methods entail a high potential to boost the sensitivity of NMR. Even though the Signal Amplification by Reversible Exchange (SABRE) approach uses para-enriched hydrogen, p-H-2, to repeatedly achieve high polarization levels on target molecules without altering their chemical structure, such studies are often limited to batch experiments in NMR tubes. Alternatively, this work introduces a continuous flow setup including a membrane reactor for the p-H-2, supply and consecutive detection in a 1 T NMR spectrometer. Two SABRE substrates pyridine and nicotinamide were hyperpolarized, and more than 1000-fold signal enhancement was found. Our strategy combines low-field NMR spectrometry and a membrane flow reactor. This enables precise control of the experimental conditions such as liquid and gas pressures, and volume flow for ensuring repeatable maximum polarization. (C) 2018 Elsevier Inc. All rights reserved.