title: NMR chromatography using microemulsion systems.
abstract: NMR spectroscopy is an excellent tool for structural analysis of pure compounds. However, for mixtures, it performs poorly because of overlapping signals. Diffusion ordered NMR spectroscopy (DOSY) can be used to separate the spectra of compounds with widely differing molecular weights, but the separation is usually insufficient. NMR "chromatographic" methods have been developed to increase the diffusion separation but these usually introduced solids into the NMR sample that reduce resolution. Using nanostructured dispersed media, such as microemulsions, eliminates the need for suspensions of solids and brings NMR chromatography into the mainstream of NMR analytical techniques. DOSY was used in this study to resolve spectra of mixtures with no increase in line-width as compared to regular solutions. Components of a mixture are differentially dissolved into the separate 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 observed for compounds that have similar diffusion rates in conventional solvents. Examples of commercial pharmaceutical drugs were also analyzed via this new technique, and the spectra of up to six components were resolved from one sample.
authors.affiliation: The Ratner Family Chair of Chemistry, Casali Institute of Applied Chemistry, Institute of Chemistry, Edmond J. Safra Campus, Givat Ram, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
authors.forename: Chava
authors.initials: C
authors.lastname: Pemberton
authors.forename: Roy E
authors.initials: RE
authors.lastname: Hoffman
authors.forename: Abraham
authors.initials: A
authors.lastname: Aserin
authors.forename: Nissim
authors.initials: N
authors.lastname: Garti
mesh_terms: D002845:Chromatography / Q000379:methods*; D003903:Deuterium; D004655:Emulsions / Q000737:chemistry*; D054879:Halogenation; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D049329:Nanostructures / Q000737:chemistry*; D004364:Pharmaceutical Preparations / Q000737:chemistry
chemical_list: D004655:Emulsions; D004364:Pharmaceutical Preparations; D003903:Deuterium