The application of visible absorption spectroscopy to the analysis of uranium in aqueous solutions

Through assay analysis into an excess of 1M H₂SO₄ at fixed temperature a technique has been developed for uranium concentration analysis by visible absorption spectroscopy over an assay concentration range of 1.8-13.4mgU/g. Once implemented for a particular spectrophotometer and set of spectroscopic cells this technique promises to provide more rapid results than a classical method such as Davies-Gray (DG) titration analysis. While not as accurate and precise as the DG method, a comparative analysis study reveals that the spectroscopic method can analyze for uranium in well characterized uranyl(VI) solution samples to within 0.3% of the DG results. For unknown uranium solutions in which sample purity is less well defined agreement between the developed spectroscopic method and DG analysis is within 0.5%. The technique can also be used to detect the presence of impurities that impact the colorimetric analysis, as confirmed through the analysis of ruthenium contamination. Finally, extending the technique to other assay solution, 1M HNO₃, HCl and Na₂CO₃, has also been shown to be viable. Of the four aqueous media the carbonate solution yields the largest molar absorptivity value at the most intensely absorbing band, with the least impact of temperature.