钯-溴酸钾-甲基橙阻抑动力学光度法测定痕量钯

Determination of trace palladium by inhibition kinetic spectrophotometry in palladium-potassium bromate-methyl orange system

利用痕量钯(Ⅱ)能阻抑溴酸钾氧化甲基橙褪色,建立了阻抑动力学光度法测定痕量钯(Ⅱ)的新方法。建立了最佳测定条件为:在比色管中加入0.9mL 1.0mo1/L硫酸,2.0mL 0.01mo1/L溴酸钾溶液,1.1mL 0.25g/L甲基橙溶液,在75℃水浴加热19min,在波长505nm处测定了阻抑和非阻抑反应的吸光度差ΔA。钯(Ⅱ)的质量浓度在6~30ng/mL范围内与ΔA呈良好的线性关系,表观速率常数k=7.65×10^(-4)/s。表观活化能Ea=400.46kJ/mol,方法检出限为3.36×10^(-10)g/mL。实验方法可用于尘土中痕量钯(Ⅱ)的测定,结果的相对标准偏差(RSD,n=6)为3.9%~4.1%,测定结果与国标法GB/T 17418.3-2010硫脲富集-石墨炉原子吸收分光光度法的测定值基本一致。

Trace palladium （Ⅱ） could inhibit the fading of methyl orange oxidized by potassium bromate.On basis of this,a new determination method of trace palladium by inhibition kinetic spectrophotometry was established.The optimum determination conditions were obtained as follows：0.9mL of 1.0mol/L sulfuric acid,2.0mL of 0.01mol/L potassium bromate solution and 1.1mL of 0.25g/L methyl orange solution were added into a colorimeter tube;after heating in water bath at 75 ℃for 19 min,the absorbance difference（ΔA）between inhibitory reaction and non-inhibitory reaction was measured at 505 nm.The results showed thatΔAexhibited good linearity to the mass concentration of palladium in range of 6-30ng/mL.The apparent rate constant was k =7.65×10（-4）/s,the apparent activation energy was Ea=400.46kJ/mol,and the detection limit of method was 3.36×10（-10）g/mL.The proposed method could be applied to the determination of trace palladium （Ⅱ） in dust.The relative standard deviation（RSD,n=6）was3.9%-4.1%.The found results were basically consistent with those obtained by national standard method（GB/T 17418.3-2010 Graphite furnace atomic absorption spectrometry after enrichment with thiourea）.