Applications

NMR spectroscopy is today used within practically all branches of chemistry, at universities as well as industrial laboratories. A typical NMR investigation combines several types of 1D, 2D (the two-pulse sequence of the 2D NMR method can be modified in many ways, resulting in hundreds of different types of 2D NMR experiments) and sometimes even 3D or 4D experiments. The accumulated information provides often a detailed picture of the molecular structure. The complete three-dimensional structure of many proteins and other biological macromolecules in solution has been determined in this way. NMR is also used to study interactions between different molecules (e.g. enzyme – substrate, soap – water), to study molecular motions in liquids and polymers, to obtain information about rates of certain reactions and much more.

A correlation spectrum for a complicated organic molecule. The two frequency axes correspond to the resonance frequencies of protons and carbon-13. The occurrence of a signal at a certain spot means that the carbon atom which corresponds to the "latitude" in the map is directly bonded to the proton whose resonance frequency is given by the "longitude". The one-dimensional proton and carbon-13 spectra are shown below and on the side of the map.

The NMR technique is also used in medical diagnosis. The magnetic resonance imaging (MRI) instruments that are in use in many hospitals today are NMR instruments of a special kind.

A so-called MR image helps the physicians look into the body. The picture is created by exposing the subject to magnetic field gradients, which make the magnetic field slightly different at different locations in the patient's head. The picture has been taken using a technique based upon Ernst's 2D FT method.