5-(5-氰基-2-吡啶偶氮)-2,4-二氨基甲苯的合成及其与钯的显色反应

合成了新试剂 5-(5-氰基-2-吡啶偶氮)-2,4-二氨基甲苯 ( 5-CN-PADAT ),探讨了该试剂与Pd 的显色反应。实验表明:在1.2 mol/L HClO₄中,于室温下Pd 可与5-CN-PADAT反应,生成组成比为1∶1的紫红色稳定配合物。配合物的最大吸收波长位于 586 nm 处,Pd的质量浓度在 0~1.2 μg/mL 范围内符合比尔定律,线性回归方程为 A=1.110 ρ (μg/mL) ＋ 0.008 6,相关系数r=0.999 9,表观摩尔吸光系数为 1.20 × 10⁵ L · mol^-1 · cm^-1。反应在强酸介质中进行,大量常见金属离子及 1 250 倍的金,500 倍的锇,250 倍的银和铑,125 倍的铱和铂,75 倍的钌不干扰Pd的测定。方法应用于钯分子筛和钯-炭催化剂中Pd 的测定,结果与参考值相符,相对标准偏差(RSD,n=6)分别为 2.3% 和3.7%。

Synthesis of 5-(5-cyano-2-pyridylazo)-2,4-diaminotoluene and its color reaction with palladium

A new reagent 5-(5-cyano-2-pyridylazo)-2,4-diaminotoluene (5-CN-PADAT) was synthesized, and its color reaction with palladium  was studied. In 1.2 mol/L HClO₄ medium, palladiumcould react with 5-CN-PADAT at room temperature, forming a 1∶1 violet-red stable complex whose the maximum absorption wavelength was at 586 nm. Beer's law was obeyed in the range of 0-1.2 μg/mL for palladium . The linear regression equation was A=1.110 ρ (μg/mL)＋ 0.008 6, with correlation coefficient of 0.999 9 and apparent molar absorptivity of 1.20 × 10⁵ L · mol^-1·cm^-1. In strong acidic medium, common metal ions and precious metal ions did not interfere in the determination, such as Au in 1250-fold, Os in 500-fold, Ag⁺ and Rh in 250-fold, Ir and Pt in 125-fold, Ru in 75-fold. 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, with the relative standard deviation (RSD,n=6) of 2.3% and 3.7%,respectively.