Fig. 2.

Trapped ion mobility spectrometry (TIMS).A, operation principle of the single TIMS device. The upper panel shows the configuration of ion optical elements. Ions entering the vacuum through the glass capillary are deflected by 90° into the entrance funnel and focused into the TIMS tunnel. Mobility-separated ions are then sequentially released and refocused in the exit funnel for downstream mass analysis. Arrows indicate the direction of the forces from the gas flow (v_g) and the electric field (E) working on the ions. The lower panel shows the electric field strength in the different steps of the TIMS analysis (accumulate, trap, and elute) as a function of the axial position (z). B, operation principle of the dual TIMS device. Same as A, with the difference that ion accumulation and mobility analysis are spatially separated in two parts of the longer TIMS tunnel. This allows parallel operation of both parts in time and increases the TIMS duty cycle close to 100% with a short transfer time from the accumulation to the analysis part. Reprinted from Silveira et al. (36) with permission from Elsevier.