Origin and correction of magnetic field inhomogeneity at the interface in biphasic NMR samples

► To address technical issues intrinsic to slice-resolved NMR spectroscopy of interfacial systems. ► Improved spectral resolution of biphasic samples near the interface. ► Shimming common analyte(s) in a heterogeneous system. ► To dispel reports in the literature that interfacial spectral distortion is due solely to surface chemistry. ► Introduce the use of paramagnetic salts to modulate bulk solvent properties.