Inductively coupled plasma mass spectrometry (ICP-MS) has been used for the
determination of trace elements in a variety of materials. For uranium, th
e concentration of U-238 can be measured with a detection limit of less tha
n 0.1 ppt in a few minutes. However, because of the extremely low U-234 con
centrations in environmental materials, it is necessary to separate U from
the matrices and to remove interfering elements from the sample solution fo
r measurement of the U-238/U-234 ratio by ICP-MS. In this study, a simple a
nd rapid separation method for U with an extraction chromatographic resin (
TEVA resin) was developed for ICP-MS and the U isotopic ratios in phosphogy
psum samples, collected in Spain, were measured. The resin efficiently reta
ined U in 6 M HCl medium and more than 98% of the U was easily eluted with
the first 30 mL of 0.1 M HNO3. The separated solutions were free from most
of the matrix elements and the concentrations of U in the solutions ranged
from 35 to 70 ppb. The U-238/U-234 isotopic ratios in the solutions were me
asured by ICP-MS. Moreover, due to the presence of a higher number of U-235
atoms in comparison with U-234, the U-238/U-235 isotopic ratios were also
determined with high precision by ICP-MS. The results obtained agreed well
with the ratios measured by alpha-spectrometry. The method for this determi
nation is more rapid than alpha-spectrometry, and is considered to be more
suitable for environmental monitoring.