Determination of thorium and uranium in solution by laser-induced breakdown spectrometry

Laser-induced breakdown spectrometry (LIBS) has been successfully developed to quantify thorium (Th) and uranium (U) in solution using membrane-based filter paper as a sample support. The filter paper is easy to handle and the entire analysis process takes only a few minutes for each sample. The developed method provides a practical approach for fast and sensitive determination of actinides in aqueous solutions using LIBS. We obtained calibration curves for U and Th individually as well as as a mixture. We observed that the quantification of trace levels of U in a bulk amount of Th was not possible because of strong spectral interference from Th at the most intense lines of U, but traces of Th in a bulk amount of U could be determined. The concentrations of U and Th in unknown solutions were determined by use of LIBS, and these results agreed to within 4% and 2%, respectively, with the expected values. The limits of detection for Th and U were calculated from the experimental data and were in the range of a few parts per million by weight to a few tens of parts per million by weight.