2-(5-溴-2-吡啶偶氮)-5-二甲氨基苯胺与铂显色反应的研究及应用

Chromogenic Reaction of 2-(5-Bromo-2-pyridylazo)-5-dimethylaminoaniline with Platinum and Its Application

研究了显色剂２（５溴２吡啶偶氮）５二甲氨基苯胺（５ＢｒＰＡＤＭＡ）与Ｐｔ（Ⅱ）的显色反应。结果表明，在乙醇存在下，１０～３２ｍｏｌ／ＬＨ３ＰＯ４介质中，试剂与Ｐｔ（Ⅱ）１５ｍｉｎ即形成稳定的紫蓝色配合物，并至少稳定２４ｈ。该配合物的最大吸收波长位于６２８ｎｍ处，表观摩尔吸光系数为８７３×１０４Ｌ·ｍｏｌ－１·ｃｍ－１，其组成为ｎＰｔ（Ⅱ）∶ｎ５ＢｒＰＡＤＭＡ＝１∶１，Ｐｔ（Ⅱ）的质量浓度在０～１０ｍｇ／Ｌ符合比尔定律。所拟方法用于二次合金管理样及催化剂中铂的直接测定，结果与推荐值相符，精密度好，ＲＳＤ＜０．５％（ｎ＝６）。

The chromogenic reaction of platinum (Ⅱ) with 2-(5-bromo-2-pyridylazo)-5-dimethylaminoaniline (5-Br-PADMA) was studied. The results show that in presence of ethanol, Pt (Ⅱ) reacts with 5-Br-PADMA to form a royal purple complex in the medium of 1.0～3.2 mol/L H_3PO_4 with a stable period of 24 h. The ratio of nplatinum (Ⅱ)∶n5BrPADMA is 1∶1 in the complex. The maximum absorbance is at 628 nm with molar absorption of 8.73×104 L·mol-1·cm-1. Beer's law is obeyed in the range of 0～1.0 mg/L for Pt(Ⅱ). The chromogenic reaction has been applied to the spectrophotometric determination of trace Pt in catalysts and secondary alloy samples. The results are in good agreement with recommended values with precision of better than 0.5% RSD ( n =6).