A computational fluid dynamics (CFD) simulation of a Rushton impeller mixing water inside a baffled vessel was used to input steady state fluid drag forces into a discrete element method (DEM) simulation of a fine quartz particle of 60μm freely moving inside the vessel. To validate the simulated behaviour of the particle, a modular positron emission particle tracking (PEPT) camera was used to track a real quartz particle of a diameter between 53 and 63μm. The particle used as the tracer was created from a 1180μm particle labelled with 18F radionuclide inside a cyclotron beam. A comparison of typical trajectory and velocities of the particle for both the model (CFD-DEM) and the measurement (PEPT) is presented. The results show that the simulation approach used is suitable to represent the behaviour of small particle of this type in water like fluid as similar trajectories and velocities are present.