三波长叠加分光光度法测定微量钯的研究

Determination of Microamounts of Palladium by Triple-Wavelength Overlapping Spectrophotometry

报道以2(3,5二氯2吡啶偶氮)5二甲氨基苯胺(简称为3,5diClPADMA)为显色剂,应用三波长叠加分光光度法测定微量钯的新方法。在002～16mol·L-1的H2SO4介质中,钯与试剂形成稳定的1∶1绿蓝色配合物,其在621和574nm有两个强弱不等的正吸收峰,在434nm处有一负吸收峰。3个峰的吸光度绝对值之和与钯浓度线性相关,钯浓度在0～12mg·L-1范围内符合比尔定律,表观摩尔吸光系数高达203×105L·mol-1·cm-1,比单波长法提高1倍。大量的有色金属及其它贵金属离子不干扰测定。所拟方法操作简便,灵敏度高,选择性好,用于钯精矿、合金及含钯分子筛中微量钯的直接测定,结果满意。

The method for the determination of microamounts of palladium with 2-(3, 5-dichlolor-2-pyridylazo)-5-dimethylaminoaniline (3, 5-diCl-PADMA) by triple-wavelength overlapping spectrophotometry has been developed. It's shown that in the medium of 0.02-1.6 mol(.)L(-1) H2SO4, Pd reacts with 3, 5-diCl-PADMA to form a stable 1:1 green-blue complex, which has two different positive absorption peaks and one negative absorption peak at 621 rim, 574 nm and 434 nm respectively, and their absorbance sum showed good linearity with Pd concentration. The apparent molar absorptivity is 2.03 x 10(5) L(.)mol(-1.)cm(-1), which is twice as high as that of single-wavelength spectrophotometry. Beer's law is obeyed in the range of 0-1.2 mg(.)L(-1) for palladium. Relatively large amounts of co existing elements, including other precious metal ions, can be tolerated. The method is simple, highly sensitive and selective, and has been used to the determination of microamounts of Pd in ore, alloy and molecular sieve with satisfactory results.