A method of detecting a target biochemical molecular species or at least one property correlated with the occurrence of the biochemical molecular species in a sample whose main component is water. The method includes: obtaining a sample whose main component is water; providing Functionalized Paramagnetic Particles (FPP) including a paramagnetic core and a moiety configured to interact with the target biochemical molecular species or with molecules collectively reporting on a property of the target biochemical molecular species; contacting the FPP with the sample; exposing the sample to an applied magnetic field; measuring a change in a nuclear relaxation property of the sample; and correlating the change to the presence of the biochemical molecular species in the sample or to at least one property correlated with the occurrence of the biochemical molecular species in the sample.