Voltammetric techniques have been employed to show that underpotential deposited Cu on polycrystalline Au electrodes in aqueous 0.1 M HClO4 catalyzes the reduction of purified selenate, SeO42-, to yield a layer of adsorbed copper selenide, CuxSe. Subsequent oxidation of this layer led to the loss of Cu, leaving behind adsorbed, elemental Se, which could be oxidized to selenite, SeO32-, at higher potentials. Application of this method made it possible to detect SeO42- down to nM levels. Voltammetric features observed on Au(poly) in Cu2+-free 0.1 M HClO4 containing SeO42- reported earlier in the literature could be attributed to the reduction of SeO32- impurities present in the commercial chemical. (C) The Author(s) 2016. Published by ECS. All rights reserved.