Figure 2.

Hypothetical drift distribution for a tryptic digest, highlighting three overlapping peptide ions (bottom). A mobility selection at G2 centered about the dotted line t_D1 (center) will include all three ions, which, with no activation, will all arrive at the same drift time. Collisional activation in IA2 may lead to shifts in mobility and therefore resolution of the three ions in the second drift dimension (top). Although the second drift dimension spans from the time ions are selected at G2 to the time they are detected, the true separation space is between the highest and lowest mobility species detected, and therefore the peak capacity is calculated using this range.