Chapter 6 - DOSY NMR for Drug Analysis

Abstract

This chapter appraises the application of the Diffusion Ordered SpectroscopY (DOSY) method that measures the translational self-diffusion of molecules in solution and allows a precise analysis of a complex mixture without any prior separation of the different components. The DOSY experiment differs from the usual modern NMR experiments because while modern NMR experiments are based on the analysis of the time dependence of the signal, here all the delays are kept strictly constant to abstract the measure from the relaxation phenomenon. The time dependence of modern NMR experiments is usually analyzed by some spectral analysis methods, but in the case of DOSY, the signal variation follows an exponential law, and a Laplace analysis is to be applied. These techniques help to ensure the quality of medicines and are being used by pharmaceutical analysts. Moreover, these techniques should be helpful in determining the relationships between different samples and so assist in the investigation of the sources of these drugs.