Determination of As and Sb in Steels by Electrothermal Atomic Absorption Spectrometry after Reduction, Complexation and Sorption on Activated Carbon

 A method for the preconcentration and separation of As and Sb in steel sample solutions is proposed. The analytes are reduced to their trivalent oxidation states with a mixture of ascorbic acid and potassium iodide and complexed by the ammonium salt of dithiophosphoric acid O,O-diethyl ester. The complexes are sorbed onto carbon. After desorption in a small volume of nitric acid solution, As and Sb are determined by electrothermal atomic absorption spectrometry. Iron(III) is also reduced to Fe(II), which is not complexed and is about 99.9% eliminated by the preconcentration procedure. Enrichment factors of 5 and 10 were obtained for As and Sb, respectively. The method was applied to the analysis of four certified steel samples, after acid dissolution in a microwave system and good agreement was obtained with the certified values. Received May 4, 1998. Revision February 22, 1999.