NMR spectroscopy presents a non-invasive detection tool for chemical composition determination, molecular structure elucidation, and dynamic analysis. In general NMR applications, spectral resolution is the key index determining the performance of resulting spectra. Unfortunately, NMR measurements on complex chemical and biological samples generally suffer from the challenge of spectral congestions, which is caused by abundant chemical compositions and limited chemical shift range as well as extensive J coupling multiplets in acquired 1D NMR. Additionally, adverse magnetic field condition constitutes the other factor degrading spectral resolution and hindering high-resolution measurements. Thus, an NMR method available for high-resolution applications to complex samples is greatly demanded.
Accordingly, we have proposed two types of NMR methods based on pulse sequence design and related data processing for high-resolution applications to complex chemical and biological samples, even under inhomogeneous magnetic field conditions. The first type of high-resolution methods is pure-shift based experiments1, which are designed to eliminate J coupling splittings of complex compositions and yield simplified spectra free of spectral congestion. For example, a high-resolution pure shift NMR method, named UPSIF, has been proposed to extract high-resolution 1D pure shift spectra, suitable for direct analyses on biological samples2. Although 1D pure shift NMR provides an effective manner for composition analyses of complex samples, molecular structure elucidations from J coupling networks remain infeasible. Recently, we proposed new pure shift protocol to extend 1D pure shit to 2D pure shit COSY, TOCSY, even high-dimension pure shift DOSY3, benefitting to complex sample detection. Secondly, based on the spin singlet-filtered mechanism4, we propose another NMR approach to individually extract the desired signals from congested NMR resonances or other interferential background signals, thus achieving high-resolution detection for complex chemical and biological samples.