DETERMINATION OF TRACES OF URANIUM AND THORIUM IN (BA, SR)TIO3 FERROELECTRICS BY INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

Traces of uranium and thorium in barium(II), strontium(II) titanate (( Ba, Sr)TiO3) ferroelectric materials were determined by inductively co upled plasma mass spectrometry (ICP-MS). Samples were completely disso lved by a mixture of 1.4% H2O2 and 1.0 mol.l(-1) HNO3. For a complete separation of the analytes from the matrix elements, a two step separa tion technique involving leaching and anion-exchange was applied. By t he leaching step with HNO3 more than 90% of the matrix can be removed whereas the analytes completely remained in the solution. The anion-ex change step was carried out on a BIO.RAD AG1-X8 column with a mixture of 1.0 mol.l(-1) HF and 0.5 mol.l(-1) HNO3 as eluent. The content of u ranium and thorium was subsequently measured by ICP-MS. The detection limits (D.L.) obtained were 0.043 ng g(-1) and 0.035 ng g(-1) for U an d Th, respectively. The reproducibility was satisfactory with a relati ve standard deviation of less than 3% (at the 1 ng g(-1) level, n = 5) . The matrix concentrations in the final solution were reduced to the sub-mu g ml(-1) level which is in the range of the detection limits of USN-ICP-AES (ultrasonic nebulization-ICP-atomic emission spectroscopy ). The method was successfully applied to the determination of uranium and thorium in three synthetic (Ba, Sr)TiO3 samples spiked with the a nalytes at levels of 1, 5 and 10 ng g(-1) and three (Ba, Sr)TiO3 ferro electric samples containing sub-ng g(-1) levels of the analytes.