Spectrophotometric determination of trace cadmium with cadmium(II)-o-phenanthroline-eosin Y complex system

The color reaction conditions of cadmium  with o-phenanthroline and eosin Y(EY) was investigated.The results showed that cadmium  could react with o-phenanthroline and EY to form a stable ion complex [Cd(phen)3]EY which had maximum absorption peak at 568 nm in HAc-NaAc buffer solution at pH 5.0.Beer's law was obeyed in the concentration range of 0.02-0.8 μg/mL for cadmium.The apparent molar absorptivity was 1.07×105 L·mol-1·cm-1 and the detection limit was 11.69 μg/L.Most common irons did not interfere with the determination.The interference of high-content Ag+,Hg2+ and Ni2+ was serious and they should be separated and removed with sulphydryl cotton before determination.The proposed method has been applied to the determination of cadmium  in industrial wastewater samples,and the results were consistent with those obtained by atomic absorption spectrometry.The relative standard deviations(RSD,n=5) were 1.3%-1.6 %,and the recoveries were 98%-103%.