Figure 3.

Mass-selected TIMS distributions of PFGK(control), PFGK-C1 (propionyl), and PFGK-C3 (acrolein). TIMS utilizes an axial voltage component to trap ions along the rising edge of the electric field gradient against a flow of neutral gas that pushes ions toward the exit. When the magnitude of the electric field gradient is decreased during a scan, ions elute according to their mobility (K). Resolving power (R) is dependent upon user-defined parameters, including the voltage scan rate (δ). As demon-strated in (a), (b), and (c) above, R increases as δ decreases. In (c), major peaks corresponding to C1 and C3 are nearly baseline resolved at δ = 41.4 V s-1. Importantly, the TIMS voltage (VTIMS) is inversely proportional to K. The C3 species is observed at a greater elution voltage and therefore has a smaller K value (larger collision cross section) relative to the C1 species.