Selective determination of inorganic and organic arsenic in high salts wastewater by graphite-furnace AAS after lanthanum hydroxide coprecipitation and reductive distillation

Abstract

The selective determination of inorganic arsenic(III, V) and total organic arsenic in high salts wastewater by graphite-furnace AAS has been developed. The selective separation of inorganic arsenic in the presence of dimethylarsinic acid, monomethylarsonic acid and p-aminophenylarsonic acid was achieved by lanthanum hydroxide coprecipitation at pH 12 or more. Organic arsenic compounds were distilled as chloroarsine compounds by reductive distillation using tin(II) chloride under 2.75 M H₂SO₄ and 4 M HCl. The developed method was satisfactorily applied to real high salts wastewater. The detection limits(3σ) were 0.3 μg dm^-3 for inorganic arsenic and 2.3 μg dm^-3 for organic arsenic.