In order to establish effective treatment removal strategies for arsenic, it is important to know the actual concentrations of As(III) and As(V) in drinking waters.The distribution of As(III) and As(V) species depends on the abundance of redox-active solids, especially organic carbon, the activity of microorganisms, and the extent of diffusion of O2 from the atmosphere. In strongly reducing aquifers. A comprehensive, systematic study was conducted to determine the effect of ferrous iron on the stability of arsenic species. Based on extensive experimental results in Fe(II)-contaminated challenge water, it was found that EDTA-HAc could be used to preserve the arsenic species for at least 28 days in opaque plastic bottles.