A simple electrochemical scheme has been worked out to effectively concentrate Pt particles in a colloidal solution by application of a DC current of typically 40-80 V across the electrodes separated by 3 cm within 15 min. When the voltage was applied between the cathode and anode in the colloidal solution, the colloidal particles were separated horizontally into vacant and dense layers. The particles were finally concentrated below the bottom edge of the anode in the solution, and the boundary height of the vacant and dense layers was found to depend on the depth of the bottom edge of the anode. (C) 2009 Elsevier B.V. All rights reserved.