An apparatus for mass analysis of ions comprising: a) an ion source; b) a time-of-flight mass spectrometer for analysis of ions transmitted from the ion source; c) a filter for segmenting incoming ions according to their m/q ratio into a first group of ions and into a second group of ions, whereas the filter is coupled to the ion source and whereas the filter and the time-of-flight mass spectrometer are arranged in such a way that the ions of the first group are transmitted to the mass spectrometer and that the ions of the second group are not transmitted to the mass spectrometer; wherein d) the filter is designed in such a way that the second group consists of ions belonging to one or several narrow bands of m/q; e) the filter comprises a field generating device (21, 22, 30, 31.1...31.4) which is designed in such a way that it generates a primary confining field capable of transmitting ions towards the time-of-flight mass spectrometer as well as one or several RF fields superimposed with said primary field; characterized in that f) frequencies of the superimposed RF fields match oscillation frequencies of ions belonging to said one or several narrow bands of m/q such that these ions are resonantly excited and finally ejected from a confining area of the primary field; g) the ion source is a high current ion source, in particular an ion source providing at least 5 million ions/s, preferably at least 50 million ions/s, at an output of the ion source; h) the ion source as well as the time-of-flight mass spectrometer are constituted and operated in such a way that a flux of ions generated by the ion source causes saturation effects in the time-of-flight mass spectrometer when the ion source is directly coupled to the time-of-flight mass spectrometer; and in that i) the apparatus comprises a device for cooling the ions to be inserted into the filter, the device being designed in such a way that it generates a confining multipole field capable of transmitting ions towards the filter and that it holds a gaseous atmosphere filling a confining region of the multipole field. a) an ion source; b) a time-of-flight mass spectrometer for analysis of ions transmitted from the ion source; c) a filter for segmenting incoming ions according to their m/q ratio into a first group of ions and into a second group of ions, whereas the filter is coupled to the ion source and whereas the filter and the time-of-flight mass spectrometer are arranged in such a way that the ions of the first group are transmitted to the mass spectrometer and that the ions of the second group are not transmitted to the mass spectrometer; d) the filter is designed in such a way that the second group consists of ions belonging to one or several narrow bands of m/q; e) the filter comprises a field generating device (21, 22, 30, 31.1...31.4) which is designed in such a way that it generates a primary confining field capable of transmitting ions towards the time-of-flight mass spectrometer as well as one or several RF fields superimposed with said primary field; f) frequencies of the superimposed RF fields match oscillation frequencies of ions belonging to said one or several narrow bands of m/q such that these ions are resonantly excited and finally ejected from a confining area of the primary field; g) the ion source is a high current ion source, in particular an ion source providing at least 5 million ions/s, preferably at least 50 million ions/s, at an output of the ion source; h) the ion source as well as the time-of-flight mass spectrometer are constituted and operated in such a way that a flux of ions generated by the ion source causes saturation effects in the time-of-flight mass spectrometer when the ion source is directly coupled to the time-of-flight mass spectrometer; and in that i) the apparatus comprises a device for cooling the ions to be inserted into the filter, the device being designed in such a way that it generates a confining multipole field capable of transmitting ions towards the filter and that it holds a gaseous atmosphere filling a confining region of the multipole field.