Determination of rare earth elements in geological materials by total reflection x-ray fluorescence

Abstract

The use of a basic total reflection x-ray fluorescence (TXRF) unit coupled to a fine structure Mo x-ray tube for the determination of rare earth elements (REEs) in geological materials was investigated. Three certified reference rock materials, viz. shale AWI-1, psammite PRI-1 and schist SBO-1, were analysed using a combination of mineral acid digestion and TXRF. In general, recoveries of better than 80% were obtained for most of the elements and detection limits of the order of about 0.1 μg g−1 were obtained for the REEs from Ce to Nd with relative standard deviations (R.S.D.) in the range 6–20%. For the elements analysed using the K emission lines, the R.S.D. of the measurements ranged from 3 to 20%, with a mean value of 12% for the elements from K to Y. The R.S.D. of the measurements using this method were in general less than 15% for most of the elements considered. By analysing rare earth-bearing rocks from Mrima Hill in Kenya, satisfactory agreement between the experimental values and those available in the literature for the total rare element oxide content was obtained.