2-(5-氰基-2-吡啶偶氮)-5-二甲氨基苯胺与钴的显色反应及其应用

Color reaction of cobalt(Ⅱ)with 2-(5-cyano-2-pyridylazo)-5-dimethylaminoaniline and its application

对2-(5-氰基-2-吡啶偶氮)-5-二甲氨基苯胺(5-CN-PADMA)与钴的显色反应进行了探讨,并将其应用于实际样品中钴的测定。实验表明,在pH 4.5的HAc-NaAc缓冲溶液中,钴与5-CN-PADMA形成稳定的络合物,其最大吸收峰位于543nm,经1.2mol/L高氯酸酸化后,该络合物转化成一种较稳定的蓝色络合物,并呈现两个吸收峰,分别位于570nm和609nm。在优化的实验条件下,钴质量浓度在0.04～0.60μg/mL内与其在570mm和609nm处的吸光度加和呈线性关系,线性相关系数为0.999 8,表观摩尔吸光系数ε为1.99×105 L·mol^(-1)·cm^(-1)。将该体系应用于镍矿和钯钴炭催化剂中微量钴的测定,结果与火焰原子吸收光谱法一致,相对标准偏差(RSD,n=6)为0.50%～0.60%。

The color reaction between 2-(5-cyano-2-pyridylazo)-5-dimethylaminoaniline(5-CN-PADMA)with cobalt was investigated and it was applied for determination of cobalt in actual samples.The experiments showed that cobalt(Ⅱ)could react with 5-CN-PADMA in HAc-NaAc buffer solution at pH 4.5 to form stable complex with maximum absorption peak at 543 nm.After acidification with 1.2 mol/L HClO4,this complex was converted to a stable blue complex with two absorption peaks at 570 nm and 609 nm,respectively.Under optimized experimental conditions,it had a linear relationship between cobalt(II)with mass concentration in range of 0.04-0.60μg/mL and the absorbance sum at 570 nm and 609 nm.The linear correlation coefficient was 0.999 8.The apparent molar absorptivity wasε=1.99×105 L·mol-1·cm-1.The proposed system was applied for the determination of trace cobalt in nickel ore and palladium-cobalt carbon catalyst,and the results were consistent with those obtained by flame atomic absorption spectrometry.The relative standard deviations(RSD,n=6)were between 0.5%and 0.6%.