Superparamagnetic iron oxide nanoparticles (SPIONs) are biocompatible and their outstanding properties make them the most used magnetic nanoparticles in biomedicine . SPIONs, for instance, are used as tracer material for the new imaging modality Magnetic Particle Imaging (MPI). In this application, the particle size is of crucial importance for imaging quality. In this project, the development, the construction and implementation of a new spectrometer to measure the size of SPIONs is described. The spectrometer is based on the Cotton Mouton Effect (CME). As part of this work, the experimental setup has been established and analysis software has been implemented. First measurements with SPIONs of a hydrodynamic diameter of 100 nm have demonstrated the potential of this technique.