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.
Langmuir. 2011 Apr 19;27(8):4497-504. doi: 10.1021/la200232b. Epub 2011 Mar 15.
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.
NMR 光谱学是一种用于纯化合物结构分析的优秀工具。然而，对于混合物，由于信号重叠，其表现不佳。扩散有序 NMR 光谱学 (DOSY) 可用于分离分子量差异很大的化合物的光谱，但通常分离不充分。已经开发出 NMR“色谱”方法来增加扩散分离，但这些方法通常会将固体引入 NMR 样品中，从而降低分辨率。使用纳米结构分散介质（如微乳液）可以消除对固体悬浮液的需求，并将 NMR 色谱法引入 NMR 分析技术的主流。在这项研究中，DOSY 用于解决混合物的光谱，与常规溶液相比，线宽没有增加。混合物的成分分别溶解到微乳液的不同相中。这里使用了先前报道的微乳液和专门为此目的开发的微乳液的几个示例。这些包括完全可稀释的微乳液、氟化微乳液和完全氘化的微乳液。对于在常规溶剂中扩散速率相似的化合物，观察到高达 1.7 个数量级的对数（扩散）差异增强。还通过这项新技术分析了商业药物的实例，并且可以从一个样品中分辨出多达六种成分的光谱。
