NMR signal separation of ionic liquids by poly(sodium-p-styrenesulfonate)-assisted chromatographic NMR spectroscopy

Abstract

Diffusion-ordered nuclear magnetic resonance spectroscopy (DOSY), dubbed chromatographic NMR spectroscopy, can be used to simultaneously distinguish and identify the structures of components in a mixture according to their different diffusion coefficients. In order to improve the resolution of DOSY on the diffusion dimension, a lot of matrices have been developed to expand the application of this technique in mixture analysis. However, there is no matrix to detect the mixture of ionic liquids (ILs). Herein, we introduced a new matrix, poly(sodium-p-styrenesulfonate) (PSSNa), which can be used to fully separate the signals of a mixture of different ILs. The mixture of three imidazolium ILs of 1-butyl-3-methylimidazolium bromide, 1-allyl-3-vinylimidazolium bromide and 1-carboxymethyl-3-methylimidazolium chloride could be fully distinguished by virtue of their different interactions with PSSNa. We also investigated the influences of PSSNa amount, IL concentration and solution pH value on the signal resolution of mixtures. This work provides a scientific reference for the analysis of the other IL analytes.