罗丹明B-钍钼杂多酸-PVA体系超高灵敏光度法测定钍

Ultrasensitive Spectrophotometric Method for the Determination of Thorium with the Rhodamine B-Molybdothorate Heteropoly Acid-PVA System

研究一个新的超高灵敏、选择性测定钍的光度法。它基于罗丹明 B-钍钼杂多酸-PVA 体系形成离子缔合物。在0.93mol/L 高氯酸溶液中,缔合物的最大吸收位于570nm,表观摩尔吸光系数ε=3.50×10~6服从比尔定律范围0～0.8μg Th/25ml,测定下限1.1ng/ml(n=9),对0.02μg TH/ml 测定11次的相对标准偏差RSD=1.5%,离子缔合物的摩尔组成Th:Mo:RB=1:12:3。考察了50多种共存离子的影响,100倍量Ce(Ⅲ),50倍量 U(Ⅵ),20倍量 P(V)不干扰。以萃取法分离钍,本法已用于某些地质样品中钍的测定,结果满意。

A new ultrasensitive and selective method based on the formation of ion-association complex in the system of rhodamine B(RB)-molybdothorate heteropoly acid-polyvinyl alcohol(PVA)is investigated.The complex gives maximum adsorbance at 570nm in solution containing 0.93mol/L perchloric acid.Its apparent molar absorptivity is 3.50×10~6 L·mol^(-1)· cm^(-1).Beer's law is obeyed for thorium in the range of 0 to 0.8μg/25ml.The limit of detection is 1.1ng/ml(n=9).0.02μg/ml of thorium was analysed eleven times,the relative standard deviation was 1.5%.The molar composition of ion-association complex was found to be Th:Mo:RB=1:12:3.The influence of over 50 diverse ions were examined.There were no interference from 100-fold amount of Ce(Ⅲ),50-fold amount of U(Ⅵ),20-fold amount of P(Ⅴ)and 4-fold amount of Y(Ⅲ).The thorium was separated using a solvent extraction procedure.The method has been applied to the determination of thorium in some geological materials with satisfactory results.