Glycerol and glycerol carbonate as ultraviscous solvents for mixture analysis by NMR

► Medium-sized molecules slowly reorient in GL and GC and therefore may be individualized by spin diffusion. ► GL and GC appeared to be ultraviscous solvents of choice for the characterization of four structurally close dipeptides. ► Selective excitation and detection were implemented to eliminate the intense proton signals of the non-deuterated solvents.