Flame atomic absorption spectrometric determination of arsenic after volatilization of As(III) with chloride ions

The generation of volatile species of As(III) as a means to introduce arsen ic into a flame atomic absorption spectrometer has been studied. The method is based on the reaction between As(III) and chloride ions in sulphuric ac id medium. The reaction is performed in a discontinuous or batch mode. With this 130 mu l of a solution containing 17.5% (w/v) sodium chloride and As( III) are injected by a 500 ml.min(-1) N-2 carrier gas flow into 1 mi of con centrated sulphuric acid. The gaseous compounds generated are introduced in to 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 th e aqueous sulphuric dilution and also the use of a nitrogen how as a carrie r. This method has been used for the determination of arsenic by flame atom ic absorption spectrometry. The analytical method shows a linear response b etween the absorption at 193.7 nm line and the As(III) concentration from 1 0 to 150 mu g.ml(-1), with a reproducibility (%r.s.d.) of 4.5% and an absol ute detection limit of 182 ng. interferences have been studied and the meth od has been applied to the determination of arsenic in a liquid insecticide . The results are compared to those obtained using a standard iodometric me thod.