研究了新试剂2-(5-溴-4-甲基-2-吡啶偶氮)-5-二甲氨基苯胺(5-Br-4-CH3-PADMA)与镍(Ⅱ)的显色反应,建立了分光光度法测定镍的新方法.结果表明,在 pH 值为 4.2~6.0 的 HAc-NaAc 缓冲溶液中,在阴离子表面活性剂十二烷基硫酸钠(SDS)存在下,镍(Ⅱ)与 5-Br-4-CH3-PADMA 形成稳定的组成比为1∶2的紫色配合物,其最大吸收波长位于 567 nm 处.镍(Ⅱ)的质量浓度在0~0.40 μg/mL范围内遵守比尔定律,校准曲线的线性相关系数r=0.999 2,表观摩尔吸光系数ε=1.22×105 L·mol-1·cm-1.以硫脲和氟化铵做掩蔽剂可消除Cu2+、Fe3+ 和Pd2+等离子的干扰.方法用于铝合金中微量镍的测定,结果的相对标准偏差(RSD, n=6)为0.58%~0.98%,并与火焰原子吸收光谱法测定值一致.
The color reaction between a new reagent 2-(5-bromo-4-methyl-2-pyridylazo)-5-dimethylaminoaniline (5-Br-4-CH3-PADMA) and nickel(Ⅱ) was studied.A new determination method of nickel by spectrophotometry was established.The experimental results showed that nickel(Ⅱ) reacted with 5-Br-4-CH3-PADMA in the presence of anion surfactant sodium dodecyl sulfate (SDS) in HAc-NaAc buffer solution at pH 4.2-6.0 to form a purple complex with stable composition of 1∶2.The maximum absorption wavelength of complex was at 567 nm.The Beer's law was obeyed for nickel(Ⅱ) with concentration range of 0-0.4 μg/mL.The linear correlation coefficient of calibration curve was r=0.999 2.The apparent molar absorptivity was ε=1.22×105 L·mol-1·cm-1.The interference of Cu2+, Fe3+ and Pd2+ could be masked using thiourea and ammonium fluoride.The proposed method was applied to the determination of trace nickel in aluminum alloy.The relative standard deviations (RSD, n=6) were between 0.58% and 0.98%.The found results were consistent with those obtained by flame atomic absorption spectrometry.
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