NMR methods for deciphering molecular species at interfaces: a comparative study

Abstract

The potential of 1 H NMR for studying the structure and dynamics of solutes on either side of an interface between two immiscible liquids is analysed. First, monitoring via localised spectroscopy of the migration of a solute from an aqueous phase to an organic phase, and the measurement of its self-diffusion coefficient slice by slice within the two phases, validated the NMR approach. Next, a fast version of localised spectroscopy (Radsl-CSI) was designed and applied to track the fate of species hyperpolarized by para-hydrogen from the organic phase where they are produced to an aqueous phase.This sequence evidenced the transfer of hyperpolarised pyridine from the organic phase to the aqueous phase, with a substantial signal gain in the latter.