Basic Researches On DOSY Experiment

Diffusion-Ordered Spectroscopy NMR(DOSY-NMR) is an important method now for the determination of self-diffusion coefficient, which have now been widely used in different areas of supermolecule, molecular self-assembly, molecular probe and host-guest recognition. Based on translational motion of molecules which can be encoded by pulsed field gradient(PFG), it builds a logical linear relationship between molecular motion and spatial gradient.With the development of pulse sequence within more than50years, PFG-NMR have always been improved, experiencing the original SE, STE, LED and Bipolar Pulse Pairs(BPP). Until1992, Kevin F. Morris and Charles S. Johnson developed a2D spectrum in which signals are dispersed in the second dimension according to diffusion coefficient, contributing to the DOS Y method used now.Though of many published literatures on DOSY, systematic research on its error range and the required signal to noise ratio(S/N) haven’t been reported. Here we studied the error range of DOSY and the influence of S/N and concentration of sample, based on a large amount of experimental data. Several conclusions haven been obtained, a) Error range, as to1%, is achieved by BPP-STE as well as BPP-LED. b) The lowest S/N, from1D spectra which is extracted from DOSY and subjects the weakest gradient pulse, should reach to150, or accurate result is not expected, c) When concentration of sample is changed by2orders, a small variety of diffusion coefficient, e.x.10%or less, cannot reflect strong molecular interaction in a host-guest or self-assembly system.