NMR as a Key Analytical Tool for Complex Systems: From Fundamentals to Advanced Approaches: A Review

Analyzing complex mixtures is essential across numerous scientific fields, and Nuclear Magnetic Resonance (NMR) spectroscopy stands out as a powerful technique due to its nondestructive nature, high resolution, and ability to analyze samples in their native state, providing both structural and quantitative insights. Rather than detailing hardware advancements, this review proposes a modular analytical strategy, an adaptable workflow designed to guide the selection and combination of methods for any mixture-analysis challenge. Key advancements, such as multinuclear and multidimensional correlation experiments, solvent suppression, virtual filtration (diffusion- and relaxation-based), homonuclear decoupling, and selective excitation, are highlighted for their contributions to improved spectral resolution through enhanced signal separation and reduced peak overlap. These techniques can be applied to diverse samples, from complex molecules to complex food matrices, biofluids, and environmental mixtures. We highlight their strengths and limitations with examples to guide optimal NMR strategy design for complex mixture analysis.