FLOW-INJECTION ONLINE 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 s ystem with diethyldithiocarbamate (DDTC) Copper(LI) being used as a ca rrier for the flame atomic absorption spectrometric determination of t race cadmium, lead and nickel was developed. Sample solutions, spiked with 120 mu g ml(-1) Cu2+ and acidified to 0.5 M with hydrochloric aci d, were merged on-line with a 2.1% DDTC solution in a 'T' connector up stream of a knotted reactor. The analytes were coprecipitated with DDT C-Cu2+ and collected on the inner wall of the knotted reactor. The col lected species were eluted with isobutyl methyl ketone, and the efflue nt was transported directly into the nebulizer. Enhancement factors of 26, 45 and 22 were obtained for cadmium, lead and nickel, respectivel y with a loading period of 30 s. The detection limits (3 sigma) for ca dmium, lead and nickel were 0.23, 3.2 and 1.4 mu g l(-1) respectively, and the relative standard deviations (n=10) were 1.4% for 20 g l(-1) cadmium, 2.0% for 200 mu g l(-1) lead and 2.2% for 80 mu g l(-1) nicke l. At least 50 mg l(-1) of such metal ions as Fe3+, Al3+, Mn2+, Zn2+ a nd Co2+, and 30 mg l(-1) of Cu2+ could be tolerated. The method has be en successfully applied to the determination of trace cadmium, lead an d nickel in various water samples and a standard reference soil. (C) 1 997 Elsevier Science B.V.