铱—钼酸盐—丁基罗丹明B—PVA_（－124）体系光度法测定铱

Spectrophotometric Determination of Iridium(Ⅳ)with Molybdate ButyIrhodamineB PVA_(124)System

在聚乙烯醇（ＰＶＡ）存在下，Ｉｒ（Ⅳ）与钼酸盐和丁基罗丹明Ｂ（ＢＲＢ）形成离子缔合物。测定Ｉｒ的适宜条件为Ｃ＿（ＨＣιＯ４）＝１．３ｍｏｌ／Ｌ，Ｃ＿（ＭｏＯ＿４）￣（２－）＝１．１×￣（－３）ｍｏｌ／Ｌ，Ｃ＿（ＢＲＢ）＝３．８×１０￣（－５）ｍｏｌ／Ｌ，ＰＶＡ０．０８％。离子缔合物的最大吸收位于５７０ｎｍ，摩尔吸光系数ε值为８．７５×１０￣５Ｌ·ｍｏｌ￣（－１）·ｃｍ￣（－１），至少可稳定一周，Ｉｒ量在０～２．５μｇ／２５ｍｌ服从比尔定律，测定极限为８．３ｎｇ／ｍｌ（ｎ＝１１），对于０．０８μｇ／ｍｌＩｒ测定的相对标准偏差为２．８％（ｎ＝８）。考察了４１种共存离子的影响，其他贵金属和Ｓｂ（Ⅱ）。Ｇｅ（Ⅳ）、Ｓｉ（Ⅳ）干扰，需采用火试金分离。本法已用于某些岩矿和冶金中间产品中Ｉｒ的测定，结果满意。用平衡移动法测定缔合物的摩尔比为Ｉｒ：ＢＲＢ＝１：４，探讨了反应机理。

A new spectrophotometric method for the determination of Ir was developed based on the reaction of Ir(Ⅳ)with molybdate and butylrhod-amine B(BRB)to form an ion associated complex in the presence of polyvinyl alcohol(PVA). The optimum concentrations of perchloric acid,heptamolybdate,BRBfor the determination of Ir are 1.3,1.1×10￣(-3),and 3.8× 10￣5 mol/L respe-ctively and PVA is 0.08%. The ion associated complex exhibits maximum absorptivity at 570 nm,molar absorptivity being 8.75 ×10￣5L·mol￣(-1)· cm￣(-1)·The ion associated complex is stable for more than a week.Beer’s law is obeyed in the range of 0 to 2.5μg/25ml for Ir.The detection limit is 8.3ng/ml (n= 11)and relative standard deviation of 0.084μg/ml of Ir is 2.8%(n=8). Tolerance limits for 41 foreign ions were tested.Other noble metal ions, such as Sb(Ⅱ),Ge(Ⅳ),and Si(Ⅳ)interfered and must be separated from Ir by a fire assay.The method is feasible for the determination of Ir in some ores and metallurgical products.The molar ratio of Ir(Ⅳ)to BRB in the ion associated complex is 1 : 4 by equilibrium movement method.The reaction mechanism was discussed.