The transfer of aluminium(III) across the water/1,2-dichloroethane interface facilitated by the herbicide Prometrine (PROM) was investigated using cyclic voltammetry. In the presence of PROM in the organic phase, the transfer of Al(III) and H+ from the aqueous to the organic phase was observed and the competition between these two cations for the herbicide was analyzed at different pH values. At pH 4.50, it was possible to determine the formation of an Al(III):PROM complex in the organic phase, with a stoichiometry of 1:3 and a charge of 2(+), indicating that the species in the complex with PROM is Al(OH)(2+). (c) 2008 Elsevier Ltd. All rights reserved.