[Determination of trace copper and cadmium in water by flame atomic absorption spectrometry coupled with flow...

The flow injection on-line preconcentration with a knotted reactor (KR) system for the determination of copper and cadmium in water by flame atomic absorption spectrometry (FAAS) was described in the present paper. The precipitation preconcentration of trace copper and cadmium was achieved by on-line merging of the sample and ammonia solutions. The resultant precipitates were on-line collected by a knotted reactor (KR) without filtration, and then the authors used a process of air segmentation. A solution of 1 mol x L(-1) HNO3 was employed to dissolve the collected precipitates and to deliver the analyte into the FAAS system for on-line detection. With a sample loading flow rate of 4.4 mL x min(-1) and a preconcentration time of 90 s, the enhancement factor was 34 (for Cu) and 36 (for Cd) as compared with the conventional FAAS method. The detection limits (3sigma) are found to be 1.9 and 0.3 microg x L(-1) for copper and cadmium respectively. The precision (RSD, n = 11) was found to be 2.3% at the level of 30.0 microg x L(-1) of Cu (II), and 2.6% at the level of 20.0 microg x L(-1) of Cd (II). The proposed method has been successfully applied to the determination of Cu (II) and Cd (II) in water samples.