Photochemical Spectrophotometric Determination of Microamounts of As with AsSbMo Ternary Heteropoly Acid

A new photochemical spectrophotometric method for the determination of 0.40～1.0 mg/L As has been described. It is based on the fact that, AsSbMo ternary heteropoly cid was reduced to form its heteropoly by ultraviolet light in the medium of 0.12 mol/L H₂SO₄-4%(V/V) methanol-2.0×10^-4 mol/L Sb(Ⅲ)-2.0×10^-3 mol/L Mo(Ⅵ). The heteropoly blue has λ_max at 780 nm. The results show that this method has high sensitivity, good seletivity and easy to operate.