丁基罗丹明B-铜钨杂多酸光度法测定微量铜

Spectrophotometric Determination of Microamounts of Copper with Butyl Rhodamine B and Tungstocoppate Heteropoly Acid

在聚乙烯醇（ＰＶＡ）存在下，丁基罗丹明Ｂ（ＢＲＢ）与铜钨杂多酸形成离子缔合物。缔合物的形成条件为ｃＨ２ＳＯ４＝１．２ｍｏｌ／Ｌ，ｃＷＯ２－４＝６．１×１０－５ｍｏｌ／Ｌ，ｃＢＲＢ＝３．８×１０－５ｍｏｌ／Ｌ和ＰＶＡ０．０８％。缔合物的最大吸收波长位于５７０ｎｍ，摩尔吸光系数ε＝１．６６×１０６Ｌ·ｍｏｌ－１·ｃｍ－１，铜量在每２５ｍＬ０～０．５μｇ范围内服从比耳定律，检测限为每ｍＬ０．６５ｎｇ（ｎ＝１２），对每ｍＬ１８ｎｇＣｕ测定的ＲＳＤ为０．８５％（ｎ＝１０）。缔合物至少稳定１５０ｈ，其摩尔比为Ｃｕ∶Ｗ∶ＢＲＢ＝１∶１２∶５，红外图谱表明铜钨杂多酸具有Ｋｅｇｇｉｎ结构。考察了４０多种共存离子的影响，大多数常见元素不干扰。本法已用于天然水、自来水、降水、人发、中药和蔬菜中铜的测定，结果满意。

A new spectrophotomteric method for the determination of microamounts of copper was studied.The method is based on the reaction of butyl rhodamine B (BRB) cation with tungstocoppate heteropoly acid anion to form an ion association complex in the presence of polyvinyl alcohol (PVA).The optimum concentrations of H 2SO 4,tungstate,BRB and PVA for the determination of copper are 1.2,6.1×10 5,3 8×10 -5 mol/L and 0.08%,respectively,The maximum absorbance of the ion association complex is at 570nm.The apparent molar absorptivity is 1.66×10 6L·mol -1 ·cm -1 .Beer's law is obeyed in the range of 0～0 05μg/25mL for copper .The detection limit is 0.65 μg/mL( n =12) and relative standard deviation is 0.85% ( n =10).The ion association complex was stable for at least 150h.The molar ratio of Cu to W to BRB in the ion association complex was established to be 1∶12∶5.The influence of 45 diverse ions was examined.Most common ions do not interfere.The method can be applied to the spectrophotometric determination of microamounts of copper in some natural waters,running water,precipitation,human hairs,carrot and Coptis with satisfactory results.