An important aspect of AFT columns is that the relative efficiency in the separation process (compared to conventional columns) increases as the flow rate increases. This enables high speed separations to be undertaken with less loss in theoretical plates, as compared to a conventional column. To illustrate the performance gain of AFT columns at high volumetric flow rate plots of HETP versus flow velocity is shown for a conventional UHPLC column packed with a 1.9 μm Hypersil GOLD stationary phase and an AFT column packed with a 5 μm Hypersil GOLD stationary phase. Both columns were in 2.1 mm i.d. formats