在无机盐和阴离子表面活性剂存在下2-(5-溴-2-噻唑偶氮)-5-二乙氨基苯甲酸与镍显色反应的研究

Color Reaction Between 2-(5-Bromo-2-thiazolylazo)-5-diethylaminobenzoic Acid and Nickel(Ⅱ) in the Presence of Salt and Anionic Surfactant

本文合成了新显色剂2-(5-溴-2-噻唑偶氮)-5-二乙氨基苯甲酸(简称5-Br-TAEB),利用光度法测定了试剂的三级质子化常数,研究了它与镍显色反应的最佳条件,同时对表面活性剂及无机盐的作用机理进行了初步探讨。实验结果表明,在NaCl和NaDS存在下,pH=5.0～8.0范围内,5-Br-TAEB与镍形成稳定的蓝色络合物,络合比为Ni^(2+):5-Br-TAEB=1:2,摩尔吸光系数ε_(642)=1.23×10~5 SL·mol^(-1)·cm^(-1)。镍浓度在0～10μg/25ml范围内服从比尔定律,方法用于铝合金中镍的测定,结果满意。

A new azo reagent of 2-(5-bromo-2-thiazolylazo)-5-diethylaminobenzoic acid (5-Br-TAEB) has been synthesized and its acid-dissociation constants have been determined using spectrophotometry. A rapid and sensitive photometric method for the determination of Ni with 5-Br-TAEB has been presented and the action mechanism of surfactant and salt has been studied. The experimental results indicate that in the presence of NaDS and NaCI at pH 5.0～8.0, Ni(Ⅰ) reacts with 5-Br-TAEB to form a stable blue 1:2 complex with molar absorptivity of 1.23×10~5 L.mol^(-1).cm^(-1) at 642nm. Beer's law is obeyed in the range of 0～10μg/25ml for Ni(Ⅰ). This method has been applied to the determination of Ni(Ⅰ) in aluminium alloy with satisfactory results.