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2-(5-溴-2-吡啶偶氮)-5-二乙氨基酚(简称5-Br-PADAP)是吸光光度法测定微量金属离子的重要显色剂,用于阴离子测定亦有报道。本文发现在酸性介质中,5-Br-PADAP质子化后,可与IO_4~-和SCN~-生成紫红色的三元离子缔合物。在0.05～0.10mol·L~-硫酸溶液中,其表观摩尔吸光系数ε_(554)=6.8×10~4,缔合物组成比为5-Br-PAPAP:IO_4~-:SCN~-=1:1:1。在研究了缔合反应最佳条件的基础上,提出了测定微量IO_4~-的新方法,应用于海带中含碘量的测定,获得满意结果。 1 试剂与仪器
2- (5-bromo-2-pyridylazo) -5-diethylaminophenol (referred to as 5-Br-PADAP) is an important chromogenic reagent for the determination of trace metal ions by spectrophotometry. In this paper, we found that in acid medium, 5-Br-PADAP protonated with IO_4 ~ - and SCN ~ - generated purple red ternary ion association. The apparent molar absorptivity ε_ (554) = 6.8 × 10 ~ 4 in 0.05 ~ 0.10mol·L ~ -sulfuric acid solution and the ratio of 5-Br-PAPAP: IO_4 ~ -: SCN ~ - = 1: 1: 1. On the basis of studying the optimal conditions of the association reaction, a new method for determination of trace IO_ (4 ~) was proposed. The method was applied to the determination of iodine in kelp and the satisfactory results were obtained. 1 Reagents and instruments