FIGURE 4.

Several common ion mobility spectrometers that result in ions of different sizes/topologies being separated in time. The mode of action of: (A) Drift Tube Ion Mobility Spectrometry (DTIMS), (i) accelerates swarms of ions with an electric field and (ii) their kinetic energy is reduced by varying amounts by collision with stationary gas molecules; (B) Trapped Ion Mobility Spectrometry (TIMS), (i) separates swarms of relatively stationary ions through collision with moving drift gas and (ii) eluting the ions in turn by decreasing the trapping potential; (C) Travelling Wave Ion Mobility Spectrometry (TWIMS) (i) pushes swarms of ions against a stationary gas using travelling voltage waves to move the ions down the cell over time, some more efficiently than others. (ii) the ions become distributed according to their topologies as they are carried along with various efficiencies and kinetic energy is reduced by varying amounts by collision with stationary gas molecules.