Flow injection on-line coprecipitation-preconcentration system using copper(II) diethyldithiocarbamate as carrier for flame atomic absorption spectrometric determination of cadmium, lead and nickel in environmental samples

A novel flow injection (FI) on-line coprecipitation-preconcentration system with diethyldithiocarbamate (DDTC) Copper(II) being used as a carrier for the flame atomic absorption spectrometric determination of trace cadmium, lead and nickel was developed. Sample solutions, spiked with 120 μg ml−1 Cu2+ and acidified to 0.5 M with hydrochloric acid, were merged online with a 2.1% DDTC solution in a ‘T’ connector upstream of a knotted reactor. The analytes were coprecipitated with DDTC-Cu2+ and collected on the inner wall of the knotted reactor. The collected species were eluted with isobutyl methyl ketone, and the effluent was transported directly into the nebulizer. Enhancement factors of 26, 45 and 22 were obtained for cadmium, lead and nickel, respectively with a loading period of 30 s. The detection limits (3σ) for cadmium, lead and nickel were 0.23, 3.2 and 1.4 μg l−1 respectively, and the relative standard deviations (n = 10) were 1.4% for 20 μg l−1 cadmium, 2.0% for 200 μg l−1 lead and 2.2% for 80 μg l−1 nickel. At least 50 mg l−1 of such metal ions as Fe3+, Al3+, Mn2+, Zn2+ and Co2+, and 30 mg l−1 of Cu2+ could be tolerated. The method has been successfully applied to the determination of trace cadmium, lead and nickel in various water samples and a standard reference soil.