The coloring reaction between 2-(5-iodine-2-pyridineazo)-5-dimethylaniline (5-I-PADMA)and palladium(Ⅱ) was investigated.The experimental results showed that,5-I-PADMA could react with palladium(Ⅱ) to form blue stable complex with molar ratio of 1 ∶ 1 in 0.6 mol/L perchloric acid medium.The maximum absorption peak of this complex was at 613 nm.Beer's law was obeyed for palladium(Ⅱ) concentration in the range of 0-0.6 μg/mL.Linear regression equation was/△A=0.828 4 ρ(μg/mL)-0.001 6 with correlation coefficient of 0.999 9 and apparent molar absorptivity of 8.82 ×104 L · mol-1 · cm-1.The proposed method was applied to the determination of trace palladium in palladium molecular sieve and ore samples.The results were in accordance with those obtained by atomic absorption spectrometry,and the relative standard deviations(n=6)were 1.2 ％-1.4％.%探讨了2-(5-碘-2-吡啶偶氮)-5-二甲氨基苯胺(5-I-PADMA)与钯(Ⅱ)的显色反应.实验表明,在0.6 mol/L高氯酸介质中,5-I-PADMA与钯(Ⅱ)反应形成摩尔比为1∶1的蓝色稳定络合物,该络合物最大吸收峰位于613 nm处.钯(Ⅱ)含量在0～0.6 μg/mL范围内符合比尔定律,线性回归方程为△A=0.828 4 ρ(μg/mL)-0.001 6,相关系数r=0.999 9,表观摩尔吸光系数为8.82×104 L·mol-1·cm-1.方法应用于钯分子筛和矿样中钯的测定,结果与原子吸收光谱法一致,相对标准偏差(n=6)为1.2％～1.4％.
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