三阶导数分光光度零点法测定含稀土岩矿中的钍

Determination of Microamount of Thorium in Rocks Containing Rare Earths by Third Derivative Spectrophotometry

本文以钍与偶氮胂Ⅲ显色体系为例,用三阶导数零点法作了研究并应用于岩矿中微量钍的测定。60μg/ml以下的稀土其三阶导数吸收线在665nm处通过基线,记录665nm处钍配合物三阶导数吸收值,0～1.25μg/ml成线性关系,存在200倍稀土可不必分离。

A highly selective method has been proposed for determining microamount of thorium by third derivative spectrophotometry, the third derivative absorbance at 663 nm is maxium for the complex of arsenaso Ⅲ-thorium, while that of lanthanum is closed to the baseline, therefore, the third derivative can eliminate the interference from certain amount of lanthanum. A linear calibration curve is obtained in the range of 0～1. 25μg/ml for Th and the amount of coexisting lanthanum is to erable in less than 60μg/ml. This method can be used to determine ppm level of thorium in rocks containing rare earths without prior seperation. The results were in good agreement with the certified values when it was applied to the determination of thorium in some geochemical standard reference samples added 0. 2～0. 5 La and the relative standard deviation for the sample containing 52.4ppm of Th was 1. 99% (n=7).