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提出了以 2 ( 5 硝基 2 吡啶偶氮 ) 5 二甲氨基苯胺 ( 5 NO2 PADMA)作为铑、钯同时测定的新光度试剂。研究发现 ,钯、铑与试剂分别在 0 3～ 3 9mol/L高氯酸介质及 pH5 2 5～ 6 75近中性介质中 ,形成稳定络合物 ,向铑络合物中加入强酸酸化 ,该络合物不仅不被分解 ,且吸收红移、吸光度增大。作者还发现 ,铑、钯与试剂形成的络合物 ,均呈现两个强弱不等的吸收峰 ,强峰分别位于 62 0nm和 62 1nm处 ,弱峰分别位于 575nm和 584nm处。其各自的强弱峰对应的吸光度之和与溶液中铑、钯的含量具有良好的线性关系。利用双波长叠加的方法测得铑、钯的表观摩尔吸光系数分别为 2 57× 1 0 5 和 1 58×1 0 5 ,灵敏度分别为单波长测定的 1 85倍和 1 68倍。本文基于二者显色酸度的差异 ,同时又采用双波长叠加使灵敏度提高而建立了铑、钯同时测定的新方法 ,灵敏度高 ,选择性好 ,操作简便 ,用于合成样品中微量铑、钯的测定 ,结果满意。
A new photometric reagent for simultaneous determination of rhodium and palladium with 2 (5-nitropyridazoly) 5 dimethylaminoaniline (5 NO2 PADMA) was proposed. It was found that palladium, rhodium and their reagents form stable complexes in the medium of 0 3 ~ 39 mol / L perchloric acid and in the neutral medium of pH 52 5 ~ 6 75, respectively, and the addition of strong acid to rhodium complex, The complex not only does not decompose, and absorb redshift, absorbance increases. The authors also found that the complexes formed by rhodium, palladium and reagents all exhibit two strong and weak absorption peaks, with strong peaks at 62 0 and 62 1 nm, respectively, and weak peaks at 575 and 584 nm, respectively. The sum of the absorbances corresponding to their respective intensity and peak has a good linear relationship with the content of rhodium and palladium in the solution. The apparent molar absorptivities of rhodium and palladium measured by dual-wavelength superposition method were 2 57 × 10 5 and 1 58 × 10 5, respectively. The sensitivity was 1 85-fold and 1 68-fold higher than that of single-wavelength measurement, respectively. In this paper, a new method for the simultaneous determination of rhodium and palladium was established based on the difference of chromogenic and acidity between the two and the double wavelength superposition to increase the sensitivity. The method has the advantages of high sensitivity, good selectivity and simple operation, and is suitable for the determination of trace amounts of rhodium and palladium The results were satisfactory.