The sulfolane/water and sulfolane/DMSO-d6 binary NMR solvents are reported for the first time for the individual-ization of mixture components by spin diffusion, when molecular tumbling is slow due to solvent viscosity, thus strongly favouring magnetization transfer by dipolar cross relaxation. All 1 H nuclei resonances within the same molecule tend to correlate in a 2D NOESY spectrum, opening the way to mixture analysis. Till now, analysis of organic compounds by NMR spin diffusion in viscous solvents involved 1 H, 13 C, 15 N and 19 F.We offer a new way to analyse mixtures by considering 31 P nuclei as chemical shift markers. We report the individualization of four polar dipeptides and of four non-polar phosphorus-containing compounds respectively dissolved in sulfolane/water and sulfolane/DMSO-d6 solvents blends by means of homonuclear selective 1D and 2D 1 H experiments and a heteronuclear 2D 1 H-31 P HSQC-NOESY experiment by taking advantage from spin diffusion. The name ViscY is proposed to refer to the class of all NMR spectroscopy experiments that rely on viscous solvents for mixture analysis.