Abstract:

NMR spectroscopy is an excellent tool for structural anal. of pure compds. However, for mixts., it performs poorly because of overlapping signals. Diffusion ordered NMR spectroscopy (DOSY) can be used to sep. the spectra of compds. with widely differing mol. wts., but the sepn. is usually insufficient. NMR chromatog. methods were developed to increase the diffusion sepn. but these usually introduced solids into the NMR sample that reduce resoln. Using nanostructured dispersed media, such as microemulsions, eliminates the need for suspensions of solids and brings NMR chromatog. into the mainstream of NMR anal. techniques. DOSY was used in this study to resolve spectra of mixts. with no increase in line-width as compared to regular solns. Components of a mixt. are differentially dissolved into the sep. phases of the microemulsions. Several examples of previously reported microemulsions and those specifically developed for this purpose were used here. These include a fully dilutable microemulsion, a fluorinated microemulsion, and a fully deuterated microemulsion. Log(diffusion) difference enhancements of up to 1.7 orders of magnitude were obsd. for compds. that have similar diffusion rates in conventional solvents. Examples of com. pharmaceutical drugs were also analyzed via this new technique, and the spectra of up to six components were resolved from one sample. [on SciFinder(R)]