A method of mixing magnetic particles (3) in a reaction chamber (2) that is part of a microfluidic device and that contains the said particles in suspension, comprises the steps: (a) providing an electromagnetic means (1,1′,6,7) to generate magnetic field sequences having polarity and intensity that vary in time and a magnetic field gradient that covers the whole space of the said reaction chamber (2); (b) applying a first magnetic field sequence to separate or confine the particles (3) so the particles occupy a sub-volume in the volume of the reaction chamber (2); (c) injecting a defined volume of the said reagent in the reaction chamber; and (d) applying a second magnetic field sequence to leads the particles (3) to be homogenously distributed and dynamically moving over a substantial portion of the whole reaction chamber volume.