Paramagnetic substances chemical shifts

The experimental setup consists of two coaxial tubes (Fig. 4.6) [18], one of which, e.g. the inner one, containing a solution of an inert probe substance and the paramagnetic solute, and the other containing a solution of only the inert probe substance in the same solvent. The shifts of the probe substance differ in the two solutions, and two different signals are observed. Their chemical shift separation is measured, and the experiment repeated with the same solution in the outer... 

Additional substances are sometimes added to the sample solution in order to facilitate measurements or to provide an internal reference for chemical shift or quantitation. Certain experiments benefit from the use of a small amount of a paramagnetic relaxation agent such as chromium(III) acetylacetonate (Secs. II.D.4 and II.G). A chemical-shift reference standard may be added if exact shifts are required. Some quantitative analyses employ an internal spin-counting intensity reference such a standard must not interfere with the sample spectrum. If the reference material is inert, it can be added directly to the sample. If it might react with the sample, the... 

The transport of substances between the inside and outside of red cells can be monitored using NMR if the resonances from the two environments have different chemical shifts or intensities. Also, resonances outside the cell can be selectively broadened by the addition of paramagnetic species that do not cross the red cell membrane. Those used include the ferric complex of desferrioxamine, dysprosium-DTPA and the copper-cyclohexanediaminetetraacetic acid complex. To measure the rate of influx of a compound into red cells, the compound is added with the paramagnetic agent to a red cell suspension and the intensity of the resonance from the intracellular component is monitored as a function of time. This approach has been used to study the transport of glycerol, alanine lactate, choline and glycylglycine. The time scale that can be addressed covers the range of ms to hours. 

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