Microtesla SABRE Enables 10% Nitrogen-15 Nuclear Spin Polarization

Parahydrogen is demonstrated to efficiently transfer its nuclear spin hyperpolarization to nitrogen-15 in pyridine and nicotinamide (vitamin B-3 amide) by conducting signal amplification by reversible exchange (SABRE) at microtesla fields within a magnetic shield. Following transfer of the sample from the magnetic shield chamber to a conventional NMR spectrometer, the N-15 NMR signals for these molecules are enhanced by similar to 30,000- and similar to 20,000-fold at 9.4 T, corresponding to similar to 10% and similar to 7% nuclear spin polarization, respectively. This method, dubbed SABRE in shield enables alignment transfer to heteronuclei or SABRE-SHEATH, promises to be a simple, cost-effective way to hyperpolarize heteronuclei. It may be particularly useful for in vivo applications because of longer hyperpolarization lifetimes, lack of background signal, and facile chemical-shift discrimination of different species.