Speciation arsenic(III) and arsenic(V) in natural water by graphite furnace AAS after coprecipitation with a copper-pyrrolidinedithiocarbamate complex

Miniaturized coprecipitation with a copper-pyrrolidinedithiocarbamate (PDC) complex was studied for the preconcentration of mu g/l levels of inorganic As (III) and As (V) in natural water. Arsenic(III) in a 10 ml of water sample could be coprecipitated with Cu(PCD)(2) at pH 5.3, while under the same conditions As(V) remained in solution. The precipitate was collected on a 10 mu m membrane filter using a mini-column, and then dissolved in 225 mu l of nitric acid(1 + 2) and 225 mu l of 4% hydrogen peroxide with ultrasonic irradiation. The resulting solution was transferred into a collection vial by centrifugation. After the addition of 50 mu l of water, the As(III) concentration was determined by GFAAS. A 20-fold preconcentration factor was obtained by this procedure. Arsenic(V) can be collected, as As(III), after reduction with L-CySteine. The As(V) concentration was obtained by subtracting the As(III) concentration from total the arsenic concentration. The detection limit(3 sigma) was found to be 0.034 mu g/l of As(III) in the initial solution. The interference of various metal ions was investigated with a mixture of metal ions at concentrations approximately equal to, or exceeding, those normally found in natural water. The mixtures of metal ions tested were found not to cause severe interferences with the determination of As (III) and As (V). The proposed method was successfully applied to river water and seawater samples.