Design and characterization of selected microemulsions as media for NMR chromatography

作者：Hoffman Roy E^*; Darmon Eliezer; Aserin Abraham; Garti Nissim

来源：Colloids and Surfaces A: Physicochemical and Engineering Aspects , 2016, 507: 218-226.

DOI：10.1016/j.colsurfa.2016.08.009

• Phase diagram
• Surfactant
• Self-diffusion
• Chemical shift
• Electrical conductivity
• SAXS

NMR chromatography is a promising and superior alternative to NMR spectroscopy for analyzing mixtures since it simultaneously separates the spectra of the compounds and supplies information about their structure. This implies that there is no need for extraction, purification or synthesis of standards, that are expensive, time consuming and usually impractical. The main aim of NMR chromatography is to increase the differences in the diffusivities of different analytes in a mixture, allowing them to be more easily and reliably identified.
The selection of surfactants and other components of microemulsions for the best performance as NMR chromatographic media was studied. Attention was focused on the selection of the proper cosolvent in three types of water-dilutable microemulsions: two anionic (deuterated ionic and the previously published fluorinated ionic) and one nonionic (undeuterated Tween-based). The diffusivities of several analytes are compared. The study also examines the effect of dilution and determines the best compositions for the NMR chromatography performance.
For the anionic microemulsions, 1-butanol was found to be the most promising cosurfactant in the deuterated system 1-butanol-d(10):toluene-d(8):SDS-d(25) in a 6:3:1 weight-ratio diluted by D2O. This composition, diluted with a 85 wt% D2O, formed a microemulsion that was even stable at relatively elevated temperatures (70 degrees C) and can serve as good medium for chromatographic NMR. Another possibility that was studied consists of nonionic-based microemulsions of isopropyl alcohol (IPA) in IPA:toluene:Tween 20 that could also be easily diluted indefinitely with water. IPA was found to be a very efficient cosurfactant at resolving diffusivities of all the components. However, the lack of availability of deuterated Tween makes it impractical for use as an NMR chromatography formulation.

• 出版日期2016-10-20