Amplification-spectrophotometric determination of arsenic

Abstract

Arsenic in submicroamounts is determined by use of the iron(II) ferrozine complex and measurement of the absorbance of the complex at 562 nm. The arsenic in the sample is converted into 12-arsenomolybdic acid and extracted into a mixture of butyl acetate and ethanol. The extracted complex is decomposed with sodium hydroxide and the Mo(VI) liberated is reduced to Mo(III) with a Jones reductor, then oxidized back to Mo(VI) with Fe(III). The resulting Fe(II) is complexed with ferrozine, and the absorbance measured. The high sensitivity of the method is due to the chemical amplification (factor of 36) that is involved in the procedure. The apparent molar absorptivity for this method is 9.44×10⁵ 1· mole⁻¹·cm⁻¹, compared to the theoretical value of 10.04×10⁵. The overall efficiency of the conversion is 94%.