This work relates a coupling between a Rydberg electron capture (REC) source and a mass spectrometer (MS) using a quadrupole ion trap within a special operating mode. The MS instrument is only briefly described as it has already been published. The advantages of the REC are shown, i.e. no fragmentation of the molecule occurs during charge exchange with the Rydberg xenon atoms. The molecular ion lifetime seems to be sufficient to perform mass spectrometry by Fourier analysis. The experiments concern certain molecules of interest in the field of the environment having a positive electron affinity to insure Rydberg electron capture, i.e. certain polyaromatic hydrocarbons, certain polychloro-biphenyls, and one dioxin. (Int J Mass Spectrom 189 (1999) 181–188)