Ultrafast 2D benchtop NMR spectroscopy enhanced by flow Overhauser dynamic nuclear polarization

Abstract

Benchtop Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful analytical technique for the monitoring of reactions and processes due to its accessibility and lower cost compared to high-field NMR. However, benchtop NMR spectroscopy often suffers from limited sensitivity and resolution. In this work, we have combined ultrafast (UF) 2D NMR with Overhauser Dynamic Nuclear Polarization (ODNP) to tackle both problems. Compared to thermally polarized 1D NMR, UF 2D NMR provides improved spectral resolution in a single scan whereas ODNP boosts the NMR sensitivity. To demonstrate the possibility of combining UF 2D NMR with ODNP for process monitoring applications, experiments were carried out at different flow conditions. Our results show that ODNP at least compensated for the losses in sensitivity of UF 2D NMR that are normally induced by high flow velocities. Moreover, under certain flow conditions, ODNP brings additional sensitivity to UF 2D NMR spectra, with SNR increased by a factor of >3 compared to thermal equilibrium acquisitions. The methods developed in this article are expected to be beneficial for more informative and sensitive acquisitions in the context of process monitoring.