In June 1806 Sartorius joined the , Captain Francis Mason. He took part in the capture of Montevideo in February 1807, and participated in various operations in South America. He was promoted to lieutenant on 5 March 1808, into the frigate , Captain John Ayscough. There he was employed in protecting to the Greenland fisheries, before being sent to the Mediterranean Fleet, where he assisted at the reduction of the Phlegraean Islands of Ischia and Procida in June 1809, and operated in the defence of Sicily against the threatened invasion of Joachim Murat.