Studies On Determination Of Trace Uranium With Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

In this paper, a rapid and accurate method for determination of isotope composition and concentration of uranium with ICP-MS and ID-ICP-MS (isotope dilution inductive coupled plasma mass spectrometry) is developed respectively.Main factors, which effect on accuracy and precision, are discussed. Operating conditions including RF power, carrier gas pressure, model of nebulizer, Uranium concentration of sample, dwell time, etc are optimized.The influences of dead time of detector and the mass bias on the precision of determination of Uranium isotope ratio studied. After calibrated by Uranium isotope ratio reference materials, the accuracy and precision are improved.Optimum of the spike added range has been studied in detail. In order to get high precision on determination of Uranium, a proper ratio of sample to spike is found finally.The Uranium isotope ratios are measured by ICP-MS in different enriched uranium samples. After calculated, the relative uncertainty of 235U/238U is better than 4% whereas those for 234U/238U, 236u/238U are better than 10%. The ICP-MS and the TIMS gave consistent results.The concentrations of U are measured with ID-ICP-MS. the uncertainty of Uranium concentration is better than 2% for a U concentration greater than O.lngmL"1. The concentration results of U in riverine sediment reference materials and soil reference materials are good agreement with the standard values, the uncertainty is better than 4%.