The increase in width between the two flow regimes is strictly proportional to the exit speed of the analyte from the capillary -this does not depend on the ionization mode, simply on the fact that a fixed length in the capillary spends twice as much time exiting it if it is moving at half the speed. One can emulate the height reduction observed in mass mode on data measured in concentration mode by simply multiplying each peak by its speed. Equation (1) relates the speed of an analyte to its mobility, which in turn can be derived from its migration time from or . This provides the exit speed v exit as a function of migration time t M ,