Abstract:

NMR chromatog. is a promising and superior alternative to NMR spectroscopy for analyzing mixts. since it simultaneously separates the spectra of the compds. and supplies information about their structure. This implies that there is no need for extn., purifn. or synthesis of stds., that are expensive, time consuming and usually impractical. The main aim of NMR chromatog. is to increase the differences in the diffusivities of different analytes in a mixt., allowing them to be more easily and reliably identified. The selection of surfactants and other components of microemulsions for the best performance as NMR chromatog. 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 diln. and dets. the best compns. for the NMR chromatog. performance. For the anionic microemulsions, 1-butanol was found to be the most promising cosurfactant in the deuterated system 1-butanol-d10:toluene-d8:SDS-d25 in a 6:3:1 wt.-ratio dild. by D2O. This compn., dild. with a 85 wt% D2O, formed a microemulsion that was even stable at relatively elevated temps. (70 °C) and can serve as good medium for chromatog. NMR. Another possibility that was studied consists of nonionic-based microemulsions of iso-Pr alc. (IPA) in IPA:toluene:Tween 20 that could also be easily dild. 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 chromatog. formulation. [on SciFinder(R)]