碲钨杂多酸-罗丹明B测定痕量碲的研究

Study on the Determination of Trace Tellurium(Ⅳ)with Rhodamine B and Heteropoly Tungstotelluric Acid

利用碲钨杂多酸－罗丹明Ｂ（ＲＢ）－聚乙烯醇体系建立了分光光度测定痕量碲的新方法，确定了测定碲的适宜条件为〔Ｈ２ＳＯ４〕＝１．２０ｍｏｌ／Ｌ，〔ＷＯ２－４〕＝１．２×１０－４ｍｏｌ／Ｌ，〔ＲＢ〕＝５．０×１０－５ｍｏｌ／Ｌ和ＰＶＡ０．０８％。在ＰＶＡ存在下碲钨杂多酸与罗丹明Ｂ形成１∶９的离子缔合物，其最大吸收位于５６５ｎｍ，表观摩尔吸光系数ε＝１．７６×１０７，离子缔合物至少稳定２４０ｈ。测定碲的线性范围为０～０．１６μｇ／２５ｍｌ，对０１２μｇ／２５ｍｌ碲测定的相对标准偏差１．３％（ｎ＝１０）。考察了４０多种共存离子的影响，大多数常见元素不干扰，允许５００倍量Ｓｅ（Ⅳ）；４０倍量Ｃｕ２＋，Ｂｉ３＋存在。本法灵敏度高，重现性和选择好，用于烟尘中碲的测定，结果与电分析法吻合。

A new spectrophotometric method for the determination of trace tellurium(Ⅳ)is established.The method is based on the rhodamine B(RB)-heteropoly tungstotelluric acid(TeW)-Polyvinyl alcohol(PVA) system.The optimum conditions for determination of tellurium(Ⅳ) are[H 2SO 4]=1.2mol/L,[WO 2- 4]=1.2×10 -4 mol/L,=5.0×10 -5 mol/L and PVA 0.08%.Tellurium(Ⅳ)reacts with sodium tungstate and rhodamine B to form an ion-association complex.Its apparent molar absorptivity is 1.76×10 7L·mol -1 ·cm -1 at 565nm.The ion-association complex is stable at least for 240h.The linear range and detection limit for the determination of tellurium is 0-0.16μg/25ml,0 12ng/ml respectively.The relative standard deviation evaluated from determination of 0.12μg/25ml for Te(Ⅳ)is 1.3%(n=10).Over 40 foreign ions are tested for interference.Most common ions do not interfere,and 500-fold amounts of Se(Ⅳ)or 50-fold amounts Cu(Ⅱ)or Bi(Ⅲ) are tolerated.The method has high sensitivity,good reproducibility and selectivity.It is applied to the determination of Te(Ⅳ)in some smoke dust samples.The results obtained agree well with those by electroanalytical method.