The mass transfer kinetic properties of 2.1 mm I.D. columns packed with core-shell (Kinetex) and totally porous (BEH) sub-2 mu m particles, operated at high flow rates, under high pressure gradient, are investigated and discussed. The differences between their kinetic performance at low, intermediate, and high velocities are explained by the Kinetex column having a smaller longitudinal diffusion than the BEH column (due to the lower internal porous volume), a larger eddy diffusion (due to a less well-packed bed, with significant trans-column velocity biases), and a smaller amplitude of the radial temperature gradient across the column diameter generated by friction of the mobile phase percolating the bed at high flow rates. This last observation is accounted for by the heat conductivity of the Kinetex bed being three times larger than that of the BEH bed. (C) 2010 Elsevier Ltd. All rights reserved.