Promises and pitfalls in the reliable determination of233U using high resolution ICP-OES

Abstract

This study highlights that the currently employed analytical approach for the ICP-OES determination of 233U at λ = 385.950 nm is neither specific for this U isotope nor reliable and provides potential solutions for a selective and reliable quantification of 233U, 235U, and 238U using high resolution ICP-OES. While being a sensitive U wavelength region, the small isotopic line splitting of 233U (λ = 385.950 nm), 235U (λ = 385.955 nm) and 238U (λ = 385.958 nm) cannot be resolved with any commercial high resolution optical spectrometer. In addition, the width of 5.67 pm of the 233U peak, defined as full width at half maximum, is particularly larger than the 238U peak width of ∼4.3 pm, thus indicating splitting of the 233U emission signal into multiple peaks. In contrast, superior U isotopic information can be obtained from isotope specific emission lines centred around λ = 411.6 nm and λ = 424.4 nm with a spectral distance between 233U and 238U of 25 pm and 39 pm, respectively. The 233U signal of both wavelength regions, however, suffers from a potential interference with thorium that requires peak deconvolution for accurate quantification of 233U.