A method of and system for analyzing ion mobility of a sample. The sample is received by an ionization chamber, which ionizes molecules of the sample. The ionized sample is received from the ionization chamber by a drift tube coupled to the ionization chamber and propelled along a length of the drift tube in a first direction away from the ionization chamber by an electric field gradient of the drift tube. A magnitude of the electric field gradient is in view of an atmospheric pressure measurement. A drift gas is propelled through the drift tube in a second direction opposite the first direction such that different types of ionized molecules travel through the drift tube at different rates. An arrival time of each of the different types of molecules at a detector located at a second end of the drift tube opposite the first end is detected.