Instruments are disclosed for analyzing ions from about 1000 to 10,000,000 Daltons by controlling a gaseous medium through which the ions travel under the influence of an electric field so that properties of the ions, such as diameter, electrical mobility, and charge, are measured. One embodiment of the disclosed instruments include an ion source, a nozzle, a jet relaxation region, an ion accumulation region, an electronic gate, a flow chamber and an ion detector.