The invention relates to a mass spectrometric mixture analysis to determine both simple mass spectra of the substances as well as more detailed information about structures and other characteristics of the substances. The invention consists in temporally separating the substance mixture in a separating device, splitting the eluating flow of substances into at least two partial flows and measuring the substances in the different partial flows by mass spectrometry. A direct measurement provides a series of spectra whose evaluation is used for optimal control of the time at which a spectrum of another, delayed partial flow is acquired and the type of this measurement procedure. The substances of the delayed partial flows or their ions can thereby be chemically or physically modified in a variety of ways in order to provide the molecular weight as well as more detailed information.