High-Resolution Solution NMR Spectra in Inhomogeneous Magnetic Fields

A high-resolution NMR spectrum, containing fine structures such as chemical shifts and scalar-coupling multiplet patterns, is helpful for analyzing molecular composition and structure. However, there are many cases where the magnetic environments are inhomogeneous, which may lead to severe signal overlapping and blur useful spectral information in liquid samples. Recently, many NMR techniques have been proposed to regain high-resolution spectral information in inhomogeneous magnetic fields. They can be mainly classified into three types that based on intermolecular multiple- quantum coherences, nutation echoes, and spatial encoding respectively. These methods can be applied to a wide range of samples, thereby opening a way to high-resolution in vivo and ex situ NMR spectroscopy. In this review, recent developments of these methods are presented and their applicability and efficiency are analyzed.