Abstract: The invention concerns a sampling device for a mobile analysis unit, in particular a mass spectrometer (13), used for the purpose of monitoring chemical substances on ground surfaces. It possesses at least one sampling wheel which revolves around an axle and which consists of a silicone tire (5) for picking up molecules of substances to be monitored and a wheel rim (6) upon which the silicone tire is fitted. The wheel rim (6) is made of metal such as stainless steel or aluminum. This means that on the one hand contamination of the silicone tire (5) by vapors from the wheel rims (6), in the course of long-term storage of the sampling wheels in airtight, closed storage containers, is prevented. On the other hand, the invention facilitates an advantageous construction of the wheel rim (6), involving the mounting of two, thin-walled rim halves (9) with rivet holes.