in the second measurement from the sum transient a fourier transformed spectrum is derived as a result the broad band spectra of complex substance mixtures like crude oil become cleaner and misinterpretations of false peaks are minimized application_number US 201615201786 A description while the invention has been shown and described with reference to a number of different embodiments thereof it will be recognized by those of skill in the art that various changes in form and detail may be made herein without departing from the scope of the invention as defined by the appended claims in a first aspect the invention aims to suppress the 1 u03bd subharmonic signals in broad band spectra obtained by quadrupolar 2 u03c9 detection in spectra of complex mixtures of substances these signals complicate the interpretation in broad band spectra measurement the measurable transients are usually short only a few seconds reducing the achievable mass resolution to enhance the resolution by a factor of two quadrupolar 2 u03c9 detection can be applied but the 1 u03bd subharmonics disturb the spectra the first aspect relates to the 2 u03c9 measurement of the cyclotron frequency such as conducted with a quadrupolar arrangement of quarter cylindrical excitation and detection electrodes as shown by.