Suspensions of iron oxide particles, so called ferrofluids, are successfully used in various technical, biochemical and medical applications. For example they find use in the area of sensor engineering, magnetic resonance imaging (MRI) and especially magnetic particle imaging (MPI). MPI is a new tomographic imaging technique that determines the spatial distribution of superparamagnetic iron oxide nanoparticles (SPIONs). Besides a very high spatial and temporal resolution MPI provides quantitative realtime imageing. The nanoparticles cause a magnetization change that can be measured. As the particle size distribution has a huge impact on the magnetization behavior is an important parameter for optimization. While synthesizing, SPIONs particles with various dimensions are formed what necessitates a systematically separation by size. For this purpose a construction of a simple device for magnetic separation of SPIONs has been developed. First attemps of separation show the potential of this method.