This master thesis deals with sampling methods of slurries. The correct procedure to sample process streams without bias is very important in the mining and mineral industry. The investigation is focused on sampling techniques of suspensions in pressurized pipes. Based on a thorough literature survey one method is selected as the most suitable for testing. The practical tests are performed on an online laser particle sizer where splitting of the slurry stream and the following measurement preparation represent significant sub-steps. Three different sample splitters are tested. The adaptations made show positive impact on the splitting process. Furthermore, a characteristic value which correlates linear with the quality of the sampling method is presented. In addition, the specified-time delay of the mixing tank in the machine is analyzed. The online determined particle size distributions are compared to those analyzed by an apparatus of equivalent measurement principle which is located at the laboratory of the chair of mineral processing.