Magnetically active samples

NMR is not an explicitly surface - sensitive technique, but NMR data on large surface area samples (> 1 m2) have provided useful data on molecular adsorption geometries. The nucleus magnetic moment interacts with an externally applied magnetic field and provides spectra highly dependent on the nuclear environment of the sample. The signal intensity is directly proportional to the concentration of the active species. This method is limited to the analysis of magnetically active nuclei. 

Although NMR-based applications on dipolar coupling have been mainly associated with solid-state NMR or NMR of oriented samples, they have been recently applied to solution NMR for studying macromolecular structure and function in an aqueous solution [20,21]. The dipolar coupling describes a through-space interaction that arises between any two magnetically active nuclei. It depends upon the distance between two atoms, which is constant for the nuclei connected by covalent bonds such as or and the orientation of the connecting vector with respect... 

As previously mentioned, nucleus is not magnetically active for NMR analyses, but with I = 1/2 can be detected by this technique. However, since the natural abundance of is about 1.1% that of and its sensitivity is only about 1.6% that of H, the overall sensitivity of compared with H is about 1/5700. Even when this characteristic can be considered as a disadvantage in comparison to H NMR, NMR is being extensively used with excellent results for characterization of plenty of samples and their molecular arrangement. 

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