Flame Atomic Absorption Spectrometric Determination of Arsenic After Volatilization of As(III) with Chloride Ions

Abstract

The generation of volatile species of As(III) as a means to introduce arsenic into a flame atomic absorption spectrometer has been studied. The method is based on the reaction between As(III) and chloride ions in sulphuric acid medium. The reaction is per- formed in a discontinuous or batch mode. With this method 130ml of a solution containing 17.5% (w/v) sodium chloride and As(III) are injected by a 500 ml.min ˇ1 N2 carrier gas flow into 1 ml of concen- trated sulphuric acid. The gaseous compounds gener- ated are introduced into the spectrometer through the nebulizer and As is determined. The arsenic trichloride volatilization from the aqueous solutions has been obtained as consequence of two factors: the high temperature produced by the aqueous sulphuric dilution and also the use of a nitrogen flow as a carrier. This method has been used for the determination of arsenic by flame atomic absorption spectrometry. The analytical method shows a linear response between the absorption at 193.7 nm line and the As(III) concentration from 10 to 150mg.ml ˇ1 , with a reproducibility (%r.s.d.) of 4.5% and an absolute detection limit of 182 ng. Interferences have been studied and the method has been applied to the determination of arsenic in a liquid insecticide. The results are compared to those obtained using a standard iodometric method.