The electroreductions of 8-quinolinecarboxylic acid and its derivative quinmerac (a quinolinic herbicide) on mercury electrodes are studied by cyclic voltammetry and chronoamperometry. In both cases the electroreduction processes correspond to electrodimerization reactions. The quinolinic acid molecules are adsorbed with the quinoline ring flat to the mercury electrode surface. 2D instantaneous nucleation and growth, described by the NGC theory, was found to take place, together with Langmuir-type adsorption desorption. (C) 2011 Elsevier Ltd. All rights reserved.