Abstract：The color reaction conditions of cadmium （Ⅱ） with o-phenanthroline and eosin Y (EY) was investigated. The results showed that cadmium （Ⅱ） 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（Ⅱ）. 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 （Ⅱ） 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%.
