Simultaneous solvent and J-modulation suppression in PFGSTE diffusion measurements

The measurement of molecular translational diffusion in solution by NMR pulsed field gradient experiments has become an established methodology with a broad range of applications, such as the study of intermolecular interactions or complex mixture analysis. One of the greatest sources of error during the extraction of diffusion coefficients is spectral overlap between peaks of different compounds. Homonuclear scalar coupling evolution during the pulse sequence (J-modulation) is particularly notorious in this respect, as the introduced dispersive line-shape contributions decrease the spectral resolution that is of prime importance for 2D DOSY analysis. [1] WATERGATE and excitation sculpting have been the most successful solvent suppression schemes applied in diffusion experiments. [2,3] However, the long spin echoes required to accommodate the soft rf-pulses lead to significant J-modulation. The recently introduced perfect-echo WATERGATE sequence alleviates this issue by refocusing the J-evolution if certain conditions are met. [4] Here, a PFGSTE-based diffusion NMR experiment based on the Perfect-Echo WATERGATE is presented that suppresses both the solvent peak and homonuclear J-modulation artefacts. [5] An excellent quality solvent suppression is achieved next to near-perfect in-phase line-shapes. The sequence allows for long soft pulses to be applied without introducing severe J-modulation artefacts, making DOSY experiments with narrow bandwidth solvent suppression possible. Progress in implementing variations of this sequence accommodating convection compensation or multiple peak suppression will be presented. [1] Botana, A., Aguilar, J.A., Nilsson, M. and Morris, G.A. J. Magn. Res. 2011, 208, 270-278. [2] Zheng, G., Stait-Gardner, T., Kumar, P.G.A., Torres, A.M. and Price, W.S. J. Magn. Res. 2008, 191, 159-163. [3] Balayssac, S., Delsuc, M.A., Gilard, V., Prigent, Y. and Malet-Martino, M. J. Magn. Res. 2009, 196, 78-83. [4] Adams, R.W., Holroyd C.M., Aguilar, J.A., Nilsson, M. and Morris, G.A. Chem. Comm. 2013, 49, 358-360. [5] Sinnaeve, D., J. Magn. Res. 2014, 245, 24-30