Zero- to Ultralow-Field NMR Spectroscopy of Small Biomolecules

Nuclear magnetic resonance (NMR) spectroscopy is a well-established analytical technique used to study chemicals and their transformations. However, high-eld NMR spectroscopy necessitates advanced infrastructure and even cryogen-free benchtop NMR spectrometers cannot be readily assembled from commercially available components. We demonstrate construction of a portable zero-field NMR spectrometer employing a commercially available magnetometer and investigate its applications in analytical chemistry. In particular, J-spectra of small representative biomolecules [¹³C]-formic acid, [1-¹³C]-glycine, [2,3-¹³C]-fumarate, and [1-¹³C]-D-glucose were acquired and an approach relying on the presence of a transverse magnetic eld during the detection was investigated for relaxometry purposes. We found that water relaxation time strongly depends on the concentration of dissolved D-glucose in the range of 1-10 mM suggesting opportunities for indirect assessment of glucose concentration in aqueous solutions. Extending analytical capabilities of zero-field NMR to aqueous solutions of simple biomolecules (aminoacids, sugars and metabolites) and relaxation studies of aqueous solutions of glucose highlight the analytical potential of non-invasive and portable ZULF NMR sensors for applications outside of research laboratories.