Where S A (f ) is the spectral intensity of component A in zero gradient ('normal'spectrum of A), D A is its diffusion coefficient and Z encodes the different gradient amplitudes used in the experiment. Assuming that a line at a given (fixed) chemical shift f belongs to a single sample component A with a diffusion constant DA, we have: The degree of attenuation is a function of the magnetic gradient pulse amplitude (G) and occurs at a rate proportional to the diffusion coefficient (D) of the molecule. The measurement of diffusion is carried out by observing the attenuation of the NMR signals during a pulsed field gradient experiment. In a certain way, it can be regarded as a special chromatographic method for physical component separation, but unlike those techniques, it does not require any particular sample preparation or chromatographic method optimization and maintains the innate chemical environment of the sample during analysis.

NMR diffusion experiments provide a way to separate the different compounds in a mixture based on the differing translation diffusion coefficients (and therefore differences in the size and shape of the molecule, as well as physical properties of the surrounding environment such as viscosity, temperature, etc) of each chemical species in solution.

Mestrenova diffusion units