钍钼杂多酸-丁基罗丹明B测定岩矿中痕量钍

Determination of Trace Amounts of Thorium (Ⅳ) in Geological Materials with Hoteropoly Molybdothoric Acid and Butylrhodamine B

本文报道了一个灵敏度高、选择性好的测定痕量钍的新光度分析法。在聚乙烯醇（ＰＶＡ）存在下，钍钼杂多酸和丁基罗丹明Ｂ（ＢＲＢ）形成离子缔合物，其适宜条件为ｃＨＣｌＯ４＝１．３ｍｏｌ／Ｌ，ｃＭｏＯ４２－＝６．８×１０－４ｍｏｌ／Ｌ，ｃＢＲＢ＝２．７×１０－５ｍｏｌ／Ｌ，ＰＶＡ０．０８％。络合物的最大吸收波长为５７０ｎｍ，服从比耳定律范围０～０．８ｍｇ／２５ＬＴｈ，表观摩尔吸光度ε为３．６３×１０６Ｌ·ｍｏｌ－１·ｃｍ－１，测定极限１．８μｇ／Ｌ（ｎ＝１２），对０．０２ｍｇ／ＬＴｈ分析１１次的相对标准偏差为２．９％，络合物的摩尔组成Ｔｈ∶Ｍｏ∶ＢＲＢ＝１∶１２∶７。大多数常见元素、１００倍Ｃｅ（Ⅲ）、４０倍Ｕ（Ⅵ）和２０倍Ｐ（Ⅴ）不干扰钍的测定。本法已用于地质标样中钍的测定，结果满意。

A sensitive and selective spectrophotometric method for the determination of thorium was studied .Thorium(Ⅳ) and ammonium heptamolybdate tetrahydrate form molybdothoric heteropoly acid(ThMo).ThMo reacts with butylrhodamine B (BRB) to form an ion association complex in the presence of polyvinyl alcohol(PVA).The optimum conditions for the determination of Th are 1.3, 6.8×10 -4 ,2 7×10 -5 mol/L and 0.08% for perchloric acid,heptamolybdate,BRB and PVA,respectively.The ion association complex exhibits maximum absorbance at 570nm.The apparent molar absorptivity is 3.63×10 6 L·mol -1 ·cm -1 .Beer's law is obeyed in the range of 0～0 8μg/25mL for Th(Ⅳ).The limit of detection is 1.8μg/L( n =12).The relative standard deviation for 0.02mg/L Th(Ⅳ) analysed eleven times was 2.9%.The complex is stable for more than 3 months.The molar ratio of Th to Mo to BRB in the complex was established to be 1∶12∶7.The influence of over 40 diverse ions was examined.There was no interference from a large number of common ions,100 fold amounts of Ce(Ⅲ),40 fold amounts of U(Ⅵ),and 20 fold amounts of P(Ⅴ).The method is feasible for the determination of thorium in geological materials.