Probe beam deflection (PBD) was used to monitor concentration gradients adjacent to the platinum electrode surface in basic and acidic aqueous media. It was observed that the PBD technique can detect anion adsorption on platinum during a cyclic voltammetry experiment. Also, PBD can measure the potential-dependent extent of adsorption of various anions including ClO4-, H2PO4- and Cl- on the Pt electrode surface. Published by Elsevier Science S.A. All rights reserved.