Development of new ion separation techniques for short lived nuclides and the first mass measurements of 52 53K Massenspektroskopie Atomgewicht Radionuklide Kernmassenmessungen Neutronenschalenabschluss Multireflexionsflugzeitmassenspektrometrie magische Zahlen Schalenabschluss nuclear mass measurements multi reflection time of flight mass spectrometry closed neutron shell radionuclides In this thesis the first on line mass measurements of the isotopes 52 53K have been performed. These measurements by multi reflection time of flight mass spectrometry with the ISOLTRAP setup at ISOLDE CERN are linked to previously measured masses of exotic Ca isotopes which had shown an unexpected large neutron shell gap at the neutron number N = 32 for the magic proton core Z = 20. The new measurements provide the first exploration of the N = 32 neutron shell closure below the proton number Z = 20. With a measured empirical two neutron shell gap of about 3MeV for 51K the N = 32 gap is smaller as compared to that of 52Ca which measures about 4MeV but is still significantly present. This confirms that the nuclear shell effect measured for calcium isotopes is not a phenomenon purely raised by its closed proton shell configuration but is also present in potassium isotopes that possess an open proton shell and an unpaired proton. The second main objective of this thesis was the development of new techniques for efficient mass separation in Penning traps and multi reflection devices because the success of nuclear mass measurements with high precision depends crucially on the purity of the ion ensemble. The two main difficulties that have been addressed are first when the masses of the ions of interest and the masses of contaminant ions are very similar and second when the contaminant ions are predominantly present in the beam from ISOLDE. For the removal of contaminant ...