title: Mobile phase compensation to improve NMR spectral properties during solvent gradients.
abstract: A solvent compensation method based on flow injection analysis is used to obtain high quality nuclear magnetic resonance (NMR) spectra during solvent gradients. Using a binary solvent system containing D2O and CD3OD, NMR line broadening and chemical shift changes are observed with a 10% methanol per min solvent composition gradient. However, by creating a second equal but reverse gradient and combining the two solvent gradients before the NMR detector, the composition of solvent reaching the NMR flow cell is kept constant. We demonstrate a system using flow injection analysis of combining solvent gradients and show constant NMR spectral performance as a function of time as the combined flow has a constant solvent composition irrespective of the initial solvent gradient. Using this approach, methods can be developed to measure high quality NMR spectra during on-flow gradient LC-NMR experiments. The ultimate ability of this approach depends on the ability to compensate for the disturbance of the solvent gradient and reverse gradient by a pair of LC columns (the analytical and reverse gradient columns).
authors.affiliation: Department of Chemistry and the Beckman Institute, University of Illinois, Urbana, IL 61801, USA.
authors.forename: Dimuthu A
authors.initials: DA
authors.lastname: Jayawickrama
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Wolters
authors.forename: Jonathan V
authors.initials: JV
authors.lastname: Sweedler
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D012997:Solvents
chemical_list: D012997:Solvents