Abstract: The current invention is based, at least in part, on the finding that the transverse nuclear magnetic spin relaxation time T2 and the transverse nuclear magnetic spin relaxation rate R2, respectively, of protons of water molecules in an aqueous solution comprising viral particles depends on the loading status (full vs. empty) of the viral particle. Thus, one aspect of the current invention is a method for determining the ratio of loaded viral particles to empty viral particles in a sample, comprising the steps of determining a nuclear magnetic resonance (NMR) parameter related to the protons of the water molecules present in an aqueous solution comprising a mixture of loaded and empty viral particles by applying an NMR measurement to the solution, and determining the ratio of loaded viral particles to empty viral particles with the NMR parameter determined in the previous step based on a calibration function.

Abstract: The present invention relates to a separation method comprising: i) providing an aqueous solution comprising a target compound; ii) applying a separation step to the aqueous solution, thereby providing a plurality of fractions of the aqueous solution: iii) determining a concentration parameter indicating a concentration of the target compound in at least part of the fractions; iv) determining a nuclear magnetic resonance (NMR) parameter by applying an NMR measurement to the fractions, the NMR parameter indicating a nuclear magnetic spin relaxation in said at least part of the fractions; and v) determining a target parameter of said at least part of the fractions based on the concentration parameter and the nuclear magnetic resonance parameter. The present invention further relates to separation systems, uses, preparations, and methods related thereto.