US Patent 7902501 Ion mobility spectrometer and method for operation

A method for operating an ion mobility spectrometer comprises supplying an analyte substance into a reaction chamber of an ion mobility spectrometer having a closed internal gas circuit and at least one membrane inlet having an inner membrane chamber, changing at least one of flow resistances and gas paths in the closed internal gas circuit, and controlling at least one of a quantity and a concentration of analyte-containing gas flowing from the inner membrane chamber to the reaction chamber.