2-(5-硝基-4-甲基-2-吡啶偶氮)-5-二甲氨基苯胺激光热透镜光谱法测定矿石中钯

Determination of palladium in ore by laser thermal lens spectrometry with 2-(5-nirtro-4-methyl-2-pyridylazo)-5-dimethylaminoaniline

利用He-Ne激光器,观测了2-(5-硝基-4-甲基-2-吡啶偶氮)-5-二甲氨基苯胺(5-NO3-4-Me-PADMA)与Pd(Ⅱ)形成络合物的激光热透镜效应。结果表明,在1.8mol/LH2SO4介质中,并在50%丙酮(体积分数,其作用是增强热透镜信号强度)存在的情况下,5-NO3-Me-PADMA与Pd(Ⅱ)反应形成蓝绿色络合物,其最大吸收峰位于623nm处,与所用He-Ne激光器输出波长632.8nm接近,据此建立了激光热透镜光谱法(TLS)测定痕量钯的新方法。实验表明,热透镜信号强度与Pd(Ⅱ)质量浓度在5~250ng/mL范围内符合线性关系,相关系数为0.9989,方法检出限为1.5ng/mL。该法不仅灵敏度高,而且选择性佳,800倍量的Fe^3+、Co^2+和Cu^2+,500倍量的Ni^2+等常见金属离子以及25倍的Pt(Ⅳ),10倍量的Au(Ⅲ)、Rh(Ⅲ)、Ru(Ⅲ)和Os(Ⅷ),5倍量的Ir(Ⅲ)等贵金属离子不干扰钯的测定。将实验方法应用于矿石中痕量钯的测定,测得结果与火焰原子吸收光谱法(FAAS)基本一致,相对标准偏差(RSD,n=6)为0.57%~1.3%。

The laser thermal lens effect of the complex formed by palladium (Ⅱ) and 2-(5-nitro-4-methyl-2-pyridylazo)-5-dimethylaminoaniline (5-NO2-4-Me-PADMA) was observed with He-Ne laser. The experiment results showed that 5-NO2-4-Me-PADMA could react with Pd (Ⅱ) in 1.8 mol/L H2SO4 medium in presence of 50% acetone (volume fraction, the aim was to enhance the intensity of thermal lens signal) to form a green-blue complex, which exhibited a maximum absorption peak at 623 nm. It was closed to the output wavelength (i.e., 632.8 nm) of He-Ne laser. Based on these experiments, a new method for determination of trace palladium by laser thermal lens spectrometry (TLS) was established. The results indicated that the intensity of thermal lens signal was linear to the mass concentration of Pd (Ⅱ) in range of 5-250 ng/mL with correlation coefficient of 0.998 9. The detection limit of method was 1.5 ng/mL. The proposed method had high sensitivity and good selectivity. The determination of palladium was not interfered by the common metal ions such as Fe^3+, Co^2+ and Cu^2+(800-fold), Ni^2+(500-fold), Pt (Ⅳ)(25-fold), and precious metal ions such as Au (Ⅲ), Rh (Ⅲ), Ru (Ⅲ) and Os (Ⅷ)(10-fold) and Ir (Ⅲ)(5-fold). The content of trace palladium in ore was determined according to the experimental method, and the found results were basically consistent with those obtained by flame atomic absorption spectrometry (FAAS). The relative standard deviations (RSD, n=6) were between 0.57% and 1.3%.