Mobility-Ordered 2D NMR Spectroscopy for the Analysis of Ionic Mixtures

Improvements in the 2D electrophoretic NMR experiment are presented. This experiment now displays the full range of positive and negative values of electrophoretic mobilities and achieves higher resolution in the mobility dimension. The electrophoresis chamber consists of concentric cylindrical tubes with the solution under study in the inner tube and a salt solution in the annulus between the tubes. Among the advantages of this design are (a) reduced effective path length for current and (b) unidirectional flow for ions of interest. Techniques based on the reverse-precession method are used to recover signs of the mobilities, and improved resolution is obtained in the mobility dimension by replacing Fourier transformation of truncated data sets with respect to the current by a linear-prediction analysis.