A sensitive and accurate method for the determination of ultra-trace level of cadmium in environmental waters by atomic absorption spectrometry with in situ trapping hydride in iridium coated graphite tube

A sensitive and accurate method is described for the determination of ultra-trace level of cadmium in environmental waters by atomic absorption spectrometry with in situ trapping hydride in iridium coated graphite tube. Effects of the conditions for the generation and collection of cadmium hydride were investigated. Phenanthroline-Co2+ was selected as an enhancement reagent for hydride generation with good enhancing effect, and iridium coating was an effective adsorbent for in situ trapping cadmium hydride in graphite tube at 300C. Under the optimal conditions, the calibration curve was linear from 10 to 1 g L-1 with correlation coefficient of 0.9991, the detection limit (3) was 3 ng L-1, and the relative standard deviation (RSD) for 11 replicate analyses of 500 ng L-1 Cd standard solution was 1.4%. The results found by the proposed method are not significantly different from the values of four plant certified reference materials (CRMs, p = 0.05). The proposed method was applied for the determination of ultra-trace Cd in tap, river water, lake water, wastewater and fish tank water with the recovery in the range of 95.6-99.7% with RSD (n = 7) of 0.5-16%. The contents of cadmium in these water samples were in the range of 9-521 g L-1.