铱－钼酸盐－罗丹明B缔合显色反应的研究

Study on the Color Reaction of the Ion- AssociateComplex of Iridium(Ⅳ）－Molybdate- Rhodamine B System

在聚乙烯醇（ＰＶＡＶＡ）存在下，铱与钼酸盐和罗丹明Ｂ（ＲＢ）形成离了缔合物。缔台物的最大吸收位于５７０ｎｍ摩尔吸光系数ε８．３６×１０￣５’Ｌ·ｍｏｌ￣－１·ｃｍ￣－１，服从比尔定率范围为０～２．７５μｇｌｒ／２５ｍｌ。测定２．０μｇ铱的相对标准偏差为２．５％（ｎ＝７），检出限４３ｎ／ｍｌ（ｎ＝１２）。测定铱的适宜条件为ＣＨＣｌＯ＿４＝０．９３ｍｏｌ／Ｌ，Ｃ＿ＭｏＯ￣２－＿４９．０×１０～－４ｍｏｌ／Ｌ，Ｃ＿ＲＢ＝３．３×ｌ０￣－５ｍｏｌ／Ｌ，ＰＶＡＯ０８％。试验了３０多种共存离子的影响，除形成杂多酸元素和贵金属干扰外．大多数贱金属不干扰。用平衡移动法测定缔合物的摩尔比ＩｎＲＢ＝１：４，初步探讨了反应机理。所提出的方法已用于冶金产品及岩矿中铱的测定，结果满意。

A new spectrophotometric method for the determination of iridium has been developed, is based on the reaction of iridium with molybdate and rhodamine B(RB) to form an ion - associate complex in the presence of polyvinyl alcohol(PVA).The ion associate complex exhibits maximum absorptivity at 570 nm, with apparent molar absorptivity8．36 × 10~5L· mol^-1· cm^-1 Beer’s law is obeyed in the range of 0-2．75μg/25ml for lr（Ⅳ）.The detection limit is 4．3ng/25ml（n=12）and relative standard deviation of 0．08μg/ml of Ir is 2．5%。(n=7).Over 30 foreign ions were tested for interferenceOther noble metal ions, sb (Ⅲ),Ge(Ⅳ)and si (Ⅳ)interfered and had to be separated from iridium by a fire assay.The optimum conditions for the determination of lr are 0，93mol/Lof HClO_4,9．0 × 10^-4mol/L of MO^2-_4,3．3 ×10^-5mol/Lof RB and 0.08％ of PVA. The proposed method was used to determine Ir in some ores and metallurgical products.The molar ratio are established to be lr ： RB=1： 4 by the equilibrium shift method.