HETP curves acquired for the solute butylbenzene on a conventional 30 × 2.1 mm UHPLC column (solid circles) packed with 1.9 μm Hypersil GOLD particles and an AFT 50 × 2.1 mm column (hollow circles) packed with 5 μm Hypersil GOLD particles. The AFT column was operated in parallel segmented flow mode, with 21% of the solvent from eluting from the radial central exit port. Only the radial central flow was processed by the UV detector.