Mixture Analysis at Micromolar Concentrations with 2D Benchtop NMR Enhanced by SABRE Hyperpolarization

Abstract

Because of its low cost and portability, benchtop NMR has become increasingly popular over the last years. However, these low-field instruments lack sensitivity and spectral resolution, which limits their application in real-world problems, particularly at low concentrations. Here, we combine SABRE hyperpolarization with two-dimensional NMR spectroscopy on a benchtop spectrometer to gain sensitivity and spectral resolution. We employ a novel cosubstrate approach, utilizing an α-amino acid, which facilitates measurements at low micromolar concentrations. This approach enabled the complete resolution of a mixture of six N-heteroaromatic compounds at concentrations of 5 μM each, within 20 min. The power of this methodology was further tested on an extract of ground coffee, for which several analytes – estimated in the low micromolar concentration range – were identified.