Quantitative Analysis in Complex Reaction Systems: The Role of USTAR in High-Resolution NMR Spectroscopy

Le résumé fourni par la source

Nuclear magnetic resonance (NMR) has played an essential role in real-time monitoring of reaction systems. However, accurate quantification of complex reactions remains challenging due to issues such as spectral overlap mainly due to structural similarities between reactants and products, low product concentrations resulting in insufficient sensitivity, and magnetic field inhomogeneity during the reaction. We here report a selective pure shift pulse sequence, named U-STAR, which removes all scalar coupling splitting while selectively extracting target resonances from overlapping signals. U-STAR offers extremely narrow linewidths, close to the limit dictated by the transverse relaxation, and up to an order-of-magnitude increase in sensitivity over conventional single-pulse 1D 1H spectroscopy, enabling accurate spectral quantification even under severe peak overlap. The method requires only a few seconds to acquire a spectrum, rendering it ideally suited for reaction monitoring. It was successfully applied across multiple complex reaction systems, including dynamic kefir fermentation processes, polymerization reactions, and electrochemical oxidation. The results show that the USTAR consistently enables monitoring and quantifying a wide range of dynamic systems with high selectivity, sensitivity, and accuracy. This will greatly expand the capabilities of in situ NMR spectroscopy for investigating complex chemical reactions.

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