双波长叠加2-(5-溴-4-甲基-2-吡啶偶氮)-5-二甲氨苯胺分光光度法测定钯

探讨了以试剂2-(5-溴-4-甲基-2-吡啶偶氮)-5-二甲氨基苯胺(简称5-Br-4-CH₃-PADMA)为显色剂,应用双波长叠加分光光度法测定钯的方法。试验表明,在1.08 ~ 3.06 mol/L H₂SO₄中,试剂与钯形成稳定的1∶1蓝紫色络合物,该络合物呈现两个强弱不等的吸收峰,分别位于606 nm和564 nm,两个峰的吸光度之和与钯浓度线性相关,钯浓度在0 ~ 1.04 μg/mL范围内符合比尔定律,表观摩尔吸光系数 ε = 1.40 × 10⁵ L·mol^-1·cm^-1。大量常见金属离子不干扰测定。方法用于含钯分子筛和钯-炭催化剂样品中钯的测定,结果与参考值相符,相对标准偏差(RSD,n=6)为1.8%和2.8%。

Determination of palladium by dual-wavelength overlapping spectrophotometry with 2-(5-bromo-4-methyl-2-pyridylazo)-5-dimethylaminoaniline

The method for determination of palladium with 2-(5-bromo-4-methyl-2-pyridylazo)-5-dimethylaminoaniline (5-Br-4-CH₃-PADMA) by dual-wavelength overlapping spectrophotometry has been developed. The experimental results show that in the medium of 1.08-3.06 mol/L H₂SO₄, palladium reacts with 5-Br-4-CH₃-PADMA forming a stable 1∶1 blue-purple complex with two absorption peaks at 606 nm and 564 nm respectively, and the sum of absorbance at these two peaks shows good linearity with palladium concentration. Beer’s law was obeyed in the range of 0-1.04 μg/mL for palladium. The apparent molar absorptivity was 1.40 ×10⁵ L·mol^-1·cm^-1. Most common ions do not interfere the determination of palladium. The proposed method has been applied for the determination of palladium in molecular sieve and palladium-carbon catalyst, the results were consistent with the reference values. The relative standard deviation(RSD, n=6) was 1.8% and 2.8%.