Boosting <sup>1</sup> H and <sup>13</sup> C NMR signals by orders of magnitude on a bench
Charlotte Bocquelet, Nathan Rougier, Huu-Nghia Le, Laurent Veyre, Chloé Thieuleux, Roberto Melzi, Armin Purea, Daniel Banks, James Kempf, Quentin Stern, Ewoud Vaneeckhaute, Sami Jannin
Abstract
Sensitivity is often the Achilles’ heel of liquid-state nuclear magnetic resonance (NMR) experiments. This problem is perhaps most pressing at the lowest fields (e.g., 80-MHz 1 H frequency), with rapidly increasing access to NMR through benchtop systems, but also sometimes for higher-field NMR systems from 300 MHz to 1.2 GHz. Hyperpolarization by dissolution dynamic nuclear polarization (dDNP) can address this sensitivity limitation. However, dDNP implies massive and complex cryogenic and high-field instrumentation, which cannot be installed on the bench. We introduce here a compact helium-free 1-T tabletop polarizer as a simple and low-cost alternative. After freezing and polarizing the frozen analyte solutions at 77 K, we demonstrate 1 H signal enhancement factors of 100, with rapid 1-s buildup times. The high polarization is subsequently transferred by 1 H→ 13 C cross polarization (CP) to 13 C spins. Such a simple benchtop polarizer, in combination with hyperpolarizing solid matrices (HYPSOs), may open the way to replenishable hyperpolarization throughout multiple liquid-state NMR experiments.