NMRdiffusiespectroscopie

NMRdiffusiespectroscopie, often abbreviated as DOSY (Diffusion Ordered Spectroscopie), is a Nuclear Magnetic Resonance (NMR) technique used to measure the translational diffusion coefficients of molecules in a sample. It separates molecules based on their size and diffusion rate, rather than their chemical structure alone, which is the primary basis for conventional NMR spectroscopy. The fundamental principle of DOSY relies on the fact that larger molecules diffuse more slowly than smaller molecules in solution. By applying pulsed magnetic field gradients, DOSY experiments can distinguish signals originating from different diffusing species.

The technique works by correlating the NMR signal intensity with the diffusion coefficient. During the experiment, a series of magnetic field gradients are applied. Molecules that move during the time between these gradients experience different magnetic field strengths, leading to a phase shift in their NMR signal. The magnitude of this phase shift is directly proportional to the distance traveled by the molecule and, consequently, to its diffusion coefficient. By analyzing how the signal intensity of each resonance changes with varying gradient strengths or durations, a diffusion coefficient can be assigned to each distinct molecular species.

DOSY is particularly useful for analyzing complex mixtures where conventional 1D NMR spectra can be heavily overlapped and difficult to interpret. It can help identify components of a mixture, determine the aggregation state of molecules, and study molecular interactions. For instance, it can differentiate between a small molecule solute and a larger solvent molecule, or between a protein and a small ligand bound to it. Applications span various fields, including chemistry, biochemistry, and materials science, for tasks such as purity assessment, characterization of supramolecular assemblies, and identifying impurities in pharmaceuticals.