Detection of Pyridine Derivatives by SABRE Hyperpolarization at Zero Field

Zero-field nuclear magnetic resonance (NMR) recently emerged as an interesting new analytical modality. While zero-field NMR provides new capabilities, it also suffers from some limitations associated, to a great degree, with low signal amplitude. In this context, parahydrogen-induced polarization naturally complements zero-field NMR, as this hyperpolarization is active even at zero magnetic field. In turn, the efficient production of large non-equilibrium polarization is possible in zero field, boosting the signal amplitude and enabling realization of the concept of "NMR without magnets''. In this work, we present zero-field NMR studies of various hyperpolarized pyridine derivatives where the 15N isotope is present at a natural abundance (0.36%). By comparing the signals of these pyridine derivatives, which include vitamin B3, as a function of their substituents, we demonstrate unique zero-field NMR spectra, consequently establishing how chemical analysis is possible even in zero field. We also study the effect of the parahydrogen-polarization-transfer catalyst activation on the resulting hyperpolarization dynamics. All of these measurements were made using apparatus designed to allow repeated in situ hyperpolarization of these samples without affecting their composition.