An approach and method for the separation of extremely large populations of ions in the gas phase where the space charge created by the ions when accumulated in a defined volume (e.g., an ion trap) causes the ions to physically separate according to their mobility. The method involves first accumulation ions in a volume, which can be any type of trapping devise, such as a linear quadrupole ion trap, a stacked ring ion guide, or a Structures for Lossless Ion Manipulations (SLIM). The design uses ions directed into the device using any number of mechanisms, but most often a weak electric field at reduced pressure.The trapping volume confines the ions using some combination of fields generated e.g. using pseudo potentials from the application of RF voltages to electrodes and DC fields. The method and device would typically use a trapping volume that would have an extended linear path, with RF confinement on the sides, such as a multipole device or a SLIM ion path, and incorporate DC confinement at the end opposite the side where ions are injected.The injected ions move through the device along the path toward the end where there is barrier (gate) to the ions of some sort, typically from the application of a DC potential to one or more electrodes. The continued introduction of ions will cause ions to be accumulated in the device, while moving toward the gate at the end of the path due to the weak field, such as a low drift field gradient, or a low amplitude traveling wave. As the large ion population accumulates at some point the maximum number of charged species that be tolerated near the end of the device is reached (i.e. the space charge limit); i.e. the accumulating ion cloud reaches the point where the s extent of charge-charge repulsion causes undesired phenomena as well as preventing more ions from being added. Charge then continues to fill the device if still being introduced. The growing ion cloud will distort the electric fields in the volume. In this environment our data shows, surprisingly, that some significant separation of ions occurs due to the opposing weak (e.g. traveling wave) electric field and the repulsive field of the ion cloud. The ions appear to separate by their mobility, with the highest mobility ions penetrating deepest into the volume and its significant space charge ( and the region of highest charge density). The ion distribution evolves to give a somewhat better separations with time; i.e. ion actively rearrange, and move into stable distributions, rather than mixed due to diffusion as would normally be expected. The trapped large ion population can then be studied or analyzed by changing the electric fields in the volume to readout the distribution (providing information on the trapped ions). The readout can use traveling wave that cause ion a'surfing'. Key points: 1. A novel physical separation of ions have been observed 2. The separations occur due to differences in mobility of ions 3. The separation uses very large numbers of ions, such that they create substantial space charge effect; Analyses typically seek to avoid such conditions as they create problems and degrade measurement performance. 4. This work was facilitated by the use of SLIM, which makes such studies readily feasible, however, we envision implementations that use conventional technologies also; i.e. this is NOT tied to the use of SLIM