SLIC-SABRE at microtesla fields enables high levels of nuclear spin polarization without magnetic shielding

Employing nuclear spin hyperpolarization to enhance NMR sensitivity opens new horizons for metabolic studies and chemical reaction monitoring. Among the hyperpolarization techniques, Signal Amplification by Reversible Exchange (SABRE) is prominent for its ability to transfer spin order from parahydrogen to target nuclei, especially 13C and 15N, without the chemical modification of the substrate under study. Despite its power, existing implementations of SABRE require expensive equipment like radiofrequency (RF) hardware and magnetic shielding. This paper demonstrates the SLIC-SABRE method at low magnetic fields as a low-cost and efficient technique for achieving high 15N polarization using a simple setup, consisting only of a small set of magnetic coils driven by a desktop PC sound card. The method yields up to 17% polarization across various SABRE-active molecules, outperforming the conventional SABRE-SHEATH approach and significantly enhancing the accessibility of hyperpolarization techniques.