Method for measuring the mobility mass spectrometric selected ion species

Method for measuring the mobility spectra of selected ion species in an ion mobility spectrometer equipped with an ion source, an ion drift path and a mass spectrometer at the end of the ion drift region, comprising the steps of (A) of the ion current during its production or the coming out of the ion source current is modulated before entry into the ion drift path with a constant modulation function such that the modulated ion current is continuous, wherein the instantaneous frequency of the modulation function varies over a frequency range steadily (B) the ion current is fed after passing through the ion drift path of the mass spectrometer, (C) with the mass spectrometer of the time profile of the ion current of a single type of ion is measured or the time characteristics of the ion current of several types of ions are measured separately from each other, and (D) from the time profile of the ion current of an ion species is obtained by a correlation analysis with the modulation function, the mobility range of the respective ion species.