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本文报道了以新试剂2-(5-硝基-2吡啶偶氮)-5-二甲氨基苯胺(5-NO_2-PADMA)作分光光度法测定铑的新体系.结果表明,在 PH=5.25～6.75范围内,铑与 5-NO_2-PADMA形成 1:1的紫红色络合物,其 λ_(max)在 525 nm处,该络合物在 1.8mol/L的盐酸溶液中转变为绿兰色,其最大吸收峰位于620nm处,表观摩尔吸光系数为1.39×10～5L·mol～1·cm～1.反应具有良好的选择性,常见金属离子在一定范围内无干扰.铑含量为0～0.56μg/mL范围内遵守比耳定律.所拟方法操作简便,灵敏度高,用于催化剂中微量铑的测定,结果满意.
In this paper, a new reagent for the spectrophotometric determination of rhodium with 2- (5-nitro-2-pyridylazo) -5-dimethylaminoaniline (5-NO 2 -PADMA) was reported.The results showed that at pH = 5.25 ~ 6.75, rhodium forms a 1: 1 purple complex with 5-NO 2 -PADMA with a λ max of 525 nm. This complex is converted to chlor-blue in 1.8 mol / L HCl solution The maximum absorption peak is at 620 nm, and the apparent molar absorptivity is 1.39 × 10 ~ 5L · mol ~ 1 · cm ~ 1. The reaction has good selectivity and the common metal ions have no interference in a certain range. The rhodium content is Beer’s law is obeyed in the range of 0 ~ 0.56μg / mL.The proposed method is simple and convenient to operate and has high sensitivity for the determination of trace rhodium in the catalyst with satisfactory results.