3-硝基偶氮氟膦与铬的褪色反应及其应用

Fading reaction of 3-nitro fluorophosphonazo with chromium(Ⅵ) and its application

报道了新显色剂3一硝基偶氮氟膦（偶氮氟膦-mN）的合成及与铬（Ⅶ的褪色反应，并将其应用于铬的形态分析。在硝酸介质中，于85℃热水浴中加热8min，铬（Ⅷ可使偶氮氟膦-mN显著褪色，且试剂空白与褪色溶液在528nIyl处的吸光度差与0．006～0．2μg／mL范围内的铬（Ⅷ符合比尔定律，表观摩尔吸光系数e为1．87×10^5L·mol^-l·cm^-1，方法检出限为1．5×10^-3μg／mL。应用该显色体系可直接测定样品中铬（Ⅶ含量，同时加入过硫酸铵将铬（Ⅲ）氧化成铬（Ⅷ，再进行测定可得总铬的含量，两者之差即为铬（Ⅲ）含量。该显色体系用于测定多种比例的铬（Ⅷ和铬（Ⅲ）混合标准溶液中铬（Ⅷ和铬（Ⅲ）的测定，测定值均与理论值一致。该显色体系应用于电镀厂及钢铁厂的工业废液显色体系中铬（Ⅷ的测定，结果的相对标准偏差（RSD，n=5）为2．2％～3．4％，加标回收率为98％～1O3％，测定结果与二苯碳酰二肼光度法测定值一致。

The synthesis of new coloring reagent 3-nitro fluorophosphonazo(fluorophosphonazo-mN)as well as its fading reaction with chromium was reported.It was applied to the state analysis of chromium.In nitric acid medium,the fluorophosphonazo-mN could be significantly faded by chromium(Ⅵ) when the solution was heated in hot water bath at 85 ℃for 8min.Moreover,the Beer's law was obeyed for the absorbance difference at 528 nm between reagent blank and fading solution when the concentration of chromium(Ⅵ) was in range of 0.006-0.2μg/mL.The apparent molar absorptivity wasε=1.87×105 L·mol-1·cm-1.The detection limit of method was 1.5×10-3μg/mL.The proposed coloring system was applied to the direct determination of chromium(Ⅵ) content in sample.Meanwhile,the ammonium persulfate was added to oxidize the Cr(Ⅲ)to Cr(Ⅵ).The total content of chromium was determined,so the difference was the content of Cr(Ⅲ).This coloring system was used for the determination of Cr(Ⅵ) and Cr(Ⅲ)in mixed standard solutions with different ratios.The found results were consistent with the theoretical values.The proposed method was also applied to the determination of Cr(Ⅵ)in industrial waste solution from electroplate factory and steel plant.The relative standard deviations(RSD,n=5)were between 2.2%and 3.4%,and the recoveries of standard addition were between 98%and 103%.The found results were consistent with those obtained by the diphenylcarbazide spectrophotometry.