In Figure plot the results of the comparison against the previously known values for the mobilities of these compounds. For each of them, the mobility was computed for each run, and the maximum relative deviation with respect to the known value amongst all six replicates (three at each pressure) was taken as an indicator of the maximal potential deviation. These maximum deviations per compound were then gathered in the shown box-plots. In the case of a single marker ignoring the ramp, the variation reaches 20%. Simply including the ramp correction reduces the median to around 4% even while neglecting the correction due to pressure. Finally, using two markers and the ramp correction lowers the median to a maximal 2% deviation with respect to the known values.