Fig. 3.

Parallel accumulation–serial fragmentation (PASEF). Time lapse (top to bottom) of a single PASEF scan on a TIMS quadrupole TOF mass spectrometer. All incoming ions are trapped simultaneously in the dual TIMS device (left column). As soon as the precursors of interest (color coded) are released from the TIMS device in the order of increasing ion mobility (decreasing 1/K₀), the position of the quadrupole isolation window switches rapidly to isolate multiple precursors sequentially for fragmentation of the precursor in the collision cell (center column). The fragment ions are mass analyzed with high-resolution TOF scans at the ion mobility position of their corresponding precursor ions (right column). 1/K₀, inverse reduced ion mobility; E, electric field strength; TIMS, trapped ion mobility spectrometry.