Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The inorganic fraction of arsenic species, iAs = Sigma[As(III) + As(V)] present in fish samples can be quantified in the presence of other arsenic species also found in fishes, such as: monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and arsenobetaine (AsB). The toxic arsenic fraction was selected taking into account the dissociation constants of these arsenic species in different hydrogen ions concentration leading to the arsine formation from iAs compounds detected as As(III) by HG AAS. For thus, a microwave assisted extraction was carried out using HCl 1 mol L-1 in order to maintain the integrity of the arsenic species in this mild extraction media. Recovery experiments were done for iAs fraction, in the presence of other arsenic species. The recovery values obtained for iAs fraction added were quantitative about 87-107% (for N = 3, RSD <= 3%). The limit of detection (LOD), and the limit of quantification (LOQ), were 5 mu g kg(-1) and 16 mu g kg(-1) respectively. (C) 2016 Elsevier Ltd. All rights reserved.2137682National Counsel of Technological and Scientific Development (CNPq)Ministry of Agriculture, Livestock and Food Supply (MAPA)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)