Miniaturized coprecipitation with a copper-pyrrolidinedithiocarbamate (PDC) complex was studied for the preconcentration of µg/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 µm membrane filter using a mini-column, and then dissolved in 225 µl of nitric acid(1 2) and 225 µl of 4 hydrogen peroxide with ultrasonic irradiation. The resulting solution was transferred into a collection vial by centrifugation. After the addition of 50 µl 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 σ ) was found to be 0.034 µg/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.
A novel method for the determination of trace amounts of selenium in iron and steel has been demonstrated by a HPLC using 2,3-diaminonaphthalene (DAN) as a derivatizing reagent. Certified reference materials of iron and steel were used to prepare digestive samples by decomposition with hydrochloric acid and nitric acid followed by phosphoric acid huming. Selenium(IV) in the digestive samples was extracted with DAN into cyclohexane. The 100 µl of cyclohexane phase was injected into the HPLC with fluorometric detection. Cyclohexanetetrahydrofuran (90 : 10 v/v) mixture was used as an eluent and effluent was monitored at 380 nm and 530 nm as excitation and emission wavelength, respectively. A linear calibration was observed in the selenium concentration range from zero to 6.0 ng/ml. The detection limit (3σ) of Se(IV) was 0.12 ng/ml, which corresponded to 0.12 ppm in iron and steel samples. The good agreement between determined values with both the proposed method and GD-MS indicates that the proposed method is of great promise for the determination of selenium present in iron and steel.
form anion-exchange columns using an original alkaline solution. Therefore, the separated Cr(III) could be determined by a direct AAS measurement of the resulting effluent.
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