Abstract: The invention proposes a method of tandem mass spectrometry for use in a mass spectrometer having a known characteristic function of the mass-to-charge ratio of the ions to be analysed, characterized in that it comprises the following steps: (a) providing a primary ions source to be analysed, (b) generating a primary mass spectrum of the primary ions, without dissociation, wherein said spectrum contains primary ion peaks of occurrence, (c) from the characteristic function values at the maxima of at least some of said primary mass peaks and from the charge values associated to said peaks, determining correlation laws that all possible multiplets of characteristic function values corresponding to multiplets of charged fragments resulting from the dissociation of parent primary ions of interest corresponding to said primary mass peaks have to meet, (d) concurrently dissociating primary ions of interest associated to primary mass peaks, in order to obtain multiplets of charged fragments from each of said parent p