The size fractionation of nanoparticles on the basis of their size continues to be a major technical problem that has only been partially solved so far. Especially, a continuous classification of nanoparticles turns out as a great challenge. Thus, processes with meticulous demands in particle-size, such as targeted drug therapies, magnetic-particle hyperthermia or radiological imaging, are hard to realize due to economic reasons. Especially for particles below 1 μm there is no method that provides a multidimensional separation with narrow separation limits.
In this project, a magnetically controlled chromatography is used to achieve a size fractionation of nanoparticles. In this context, the interaction of three forces represents the relevant parameters for a successful separation: the hydrodynamic drag force, random diffusion force and the magnetic force. The method is implemented by means of a magnetisable chromatography matrix consisting of steel spheres which are magnetised with the aid of an external electromagnet. The presence of the chromatography matrix distorts the field to such an extent that bodies, like nanoparticles, are decelerated by the matrix. Since the effect of the magnetic force depends on size, shape and material of the nanoparticles, a size fractionation can be achieved. Furthermore, different nanoparticle species could be separated from each other. In order to achieve a continuous process, a multicolumn system is used. This Simulated Moving Bed (SMB) system could be adapted to different properties for a multitude of fractionation processes of nanoparticles.
Figure 1: Laboratory construction of the multi-column system
Figure 2: Schematic representation of the fractionation process