Quantitative 2D Nuclear Magnetic Resonance of Complex Mixtures: From General Analytical Homo/Heteronuclear Methods to Intrinsically Quantitative HSQC Approaches

Quantitative 2D nuclear magnetic resonance (NMR) spectroscopy has emerged as an efficient approach for the analysis of complex mixtures, in particular when peak overlap prevents the accurate quantitation of mixture components by 1D NMR. However, a variety of quantitative 2D NMR methods are available, which makes it difficult to choose the most appropriate approach to a given problem. In this review, we attempt to provide a unified description of the main quantitative 2D NMR approaches that have been described and used in recent literature. These include methods relying on the design of an external calibration workflow, as well as specific heteronuclear 2D pulse sequences that provide direct absolute quantitation. Practical considerations to implement these methodologies are provided, as well as an overview of the most recent applications. Finally, methodological and application perspectives are described in the last section.