5-(5-硝基-2-吡啶偶氮)-2,4-二氨基甲苯吸光光度法同时测定铜和钯

SIMULTANEOUS PHOTOMETRIC DETERMINATION OF COPPER AND PALLADIUM WITH 5-(5-NITRO-2-PYRIDYLAZO)-2,4-DIAMINOTOLUENE

提出用5 (5 硝基 2 吡啶偶氮) 2,4 二氨基甲苯(5 NO2 PADAT)光度法同时测定铜和钯的新体系。室温下,铜与试剂仅能在pH4.5～6.0范围内定量反应,而钯与试剂于强酸性介质中即可显色完全。基于铜配合物可被EDTA分解而钯配合物不被分解,及铜、钯配合物形成的酸度差异,实现了铜、钯的同时测定。铜浓度在0～0.7μg·ml-1、钯浓度在0～0.9μg·ml-1范围内符合比耳定律,其表观摩尔吸光系数分别为ε519Cu=6.70×104L·mol-1·cm-1,ε592Pd=1.25×105L·mol-1·cm-1。方法已成功用于矿样和电镀活化废液中铜、钯的同时测定。

It was found that at room temperature, palladium(Ⅱ) and copper(Ⅱ) react with 5-(5-nitro-2-pyridylazo)-2,4-diaminotoluene (5-NO_2-PADAT) in an acetate buffer medium around pH 5 to form stable complexes having their absorption maxima at 519nm. And in a relatively strong acid medium (e.g. in 0.06～1.5mol·L^(-1) HCl medium, 0.18～4.6mol·L^(-1) H_2SO_4 medium or 0.06～3.6mol·L^(-1) HClO_4 medium) the complex of Pd(Ⅱ) with 5-NO_2-PADAT remains stable and its absorption maxima shifts to 592nm, while copper(Ⅱ) does not react with 5-NO_2-PADAT. It was also found that in the acetate buffer medium, the complex of Cu(Ⅱ) with 5-NO_2-PADAT is decomposed by the addition of EDTA, while the complex of Pd(Ⅱ)-5-NO_2-PADAT remains unchanged. Based on these facts, a method of simultaneous photometric determination of Cu(Ⅱ) and Pd(Ⅱ) is proposed. (Beer′s) law holds in the ranges of 0～0.7μg·ml^(-1) for copper and 0～0.9μg·ml^(-1) for palladium, with their apparent molar absorptivities of ε^(519)_(Cu)=6.70×10~4L·mol^(-1)·cm^(-1) and ε^(592)_(Pd)=1.25×10~5L·mol^(-1)·cm^(-1). The proposed method has been satisfactorily applied to the analysis of ores and waste water from electroplating plants.