Colorimetric method for the determination of arsenic(III) in potable water

Abstract

A colorimetric method for the determination of arsenic(III) at a concentration of 0.002 mg l^–1 in potable water was developed. Arsenic(III) reacts quantitatively with potassium iodate in the presence of sulphuric acid and releases an equivalent amount of iodine, which imparts a pink colour to a carbon tetrachloride extract, this colour being measured at 520 nm. The method was used to differentiate between arsenic(III) and arsenic(V). No interference from arsenic(V), chloride, fluoride or nitrate was observed. Natural water samples analysed by this technique showed trace amounts of arsenic(III).