2-(5-硝基-2-吡啶偶氮)-5-二甲氨基苯胺与铑显色反应的研究及应用

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.

Colur Reaction of a 2-(5-Nitro-2-pyridylazo)-5-dimethylamino -aniline With Rhodium and Its Application

The condition for the colour reation of a reagent 2-(5-nitro-2-pyridylazo)-5-dimethylamino-aniline (5-NO2-PADMA) with rhodium was studied. The expermental results show that rhodium reacts with 5-NO2-PADMA at pH 5. 25-6. 75 to form a violet-red complex and its maximum absorbance is at 552 nm. The complex changes into a blue-violet in 1. 8 mol/L HC1 acid solution, its apparent molor absorptivity is 1. 39 X 105 L mol-1 cm-1 at 620 nm, Beer' s law is obeyed in the concentration range of 0-0. 56 ug/mL for rhodium. The ratio of rhodium to 5-N02-PADMA is 1 : 1 in the complex. The proposed method has been applied to the spectrophotometric determination of trace rhodium in catalysts with satisfactory results.