Nuclear magnetic resonance (NMR) relaxometry is an analytical method that provides information about molecular environments, even for NMR “silent” molecules (spin-0), by analyzing the properties of NMR signals versus the magnitude of the longitudinal field. Conventionally, this technique is performed at fields much higher than Earth’s magnetic field, but our work focuses on NMR relaxometry at zero and ultra-low magnetic fields (ZULFs). Operating under such conditions allows us to investigate slow (bio)chemical processes occurring on a timescale from milliseconds to seconds, which coincide with spin evolution. ZULFs also minimize T2 line broadening in heterogeneous samples resulting from magnetic susceptibility. Here, we use ZULF NMR relaxometry to analyze (bio)chemical compounds containing 1H-13C, 1H-15N, and 1H-31P spin pairs. We also detected high-quality ULF NMR spectra of human whole-blood at 0.8 μT, despite a shortening of spin relaxation by blood proteomes (e.g., hemoglobin). Information on proton relaxation times of blood, a potential early biomarker of inflammation, can be acquired in under a minute using inexpensive, portable/small-size NMR spectrometers based on atomic magnetometers.

NMR relaxometry is an analytical method that provides information about the molecular environment, including even NMR “silent” molecules (spin-0), by analyzing the properties of NMR signals versus the magnitude of the longitudinal field. Conventionally, this technique has been performed at fields much higher than Earth’s magnetic field, but in this work, we present NMR relaxometry at zero and ultra-low magnetic fields (ZULFs). Operation under ZULFs allows us to investigate many slow (bio)chemical processes, whose timescale (milliseconds-seconds) coincides with a timescale of spin evolution. ZULFs regime also limits the detrimental role of T2 dephasing, which, in heterogeneous samples, is induced by magnetic susceptibility and often leads to line broadening, hence low-resolution spectra. Finally, in contrast to their high-field NMR, ZULF NMR measurements can be performed with inexpensive, portable/small-size sensors (atomic magnetometers). Here, we use ZULF NMR relaxometry in the analysis of (bio)chemical compounds containing 1H 13C, 1H-15N, and 1H-31P spin pairs. We also detected high-quality ULF NMR spectra of human whole blood at 0.8 μT, despite a shortening of spin relaxation by blood proteomes (e.g., hemoglobin). Information on relaxation times of blood, a potential early biomarker of inflammation, can be obtained in less than a minute and without the need for a sophisticated apparatus.

Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical tool of modern science and technology. Apart from rich information that can be extracted from the frequencies of precessing nuclear spins, detection of the decay of the signals (NMR relaxometry) may reveal important information about molecular environment, including NMR-silent (spin-0) molecules. While conventionally done at high fields, in this work, we present NMR relaxometry at zero and ultra-low magnetic field (ZULF) regime. Operation under these conditions is especially promising because spin evolution occurs at timescales (milliseconds to seconds) comparable to those of many slow (bio)chemical processes allowing their investigation. It also limits the detrimental role of line-broadening induced by magnetic susceptibility. These measurements can be performed with an inexpensive, portable/small-size system. Applicability of the ZULF NMR relaxometry is demonstrated in analysis of various (bio)chemicals including 1H-13C, 1H-15N, and 1H-31P spin systems. We observed high-quality ZULF NMR spectra of human whole blood, despite a shortening of spin relaxation time of its water protons (0.3-0.4 s) induced by blood proteomes (e.g., hemoglobin). The information about the relaxation times of blood and, potentially, other biofluids, can be obtained with sample preparation in less than a minute and without the need for a sophisticated apparatus.