Extraction chromatographic separations and analysis of actinides using sequential injection techniques with on-line inductively coupled plasma mass spectrometry (ICP MS) detection

Abstract

A sequential injection (SI) separation system has been developed for separation and analysis of Am, Pu, and Np isotopes using on-line inductively coupled plasma mass spectrometry (ICP MS) detection. On-line actinide separations were carried out using an actinide-specific extraction chromatographic material (TRU-resin, Eichrom Industries, Inc. USA). Separations are demonstrated and characterized that are compatible with on-line ICP MS detection and address isobaric (²⁴¹Am/²⁴¹Pu, ²⁴⁴Pu/²⁴⁴Cm, ²³⁸U/²³⁸Pu), molecular (²³⁸UH/²³⁹Pu), and spectral (²³⁸U/²³⁷Np) interferences encountered in the analysis of Am, Pu and Np isotopic composition using ICP MS. The effects of reductive sample treatment on the extent of U matrix removal were investigated. Uranium separation factors were limited by the formation of U(IV) species, which exhibited separation behaviors similar to that of Pu(IV) and Np(IV). Nevertheless, separation factors as high as 3.0 × 10⁵ can be achieved at the 0.1 mg ml⁻¹ U concentration levels using Fe(II) sulfamate as a reductant. The sequential injection (SI) ICP MS technique has been applied towards analysis of Am, Pu, and Np isotopes in a dissolved vitrified nuclear waste sample. Results obtained using the automated separation technique with ICP MS detection were in satisfactory agreement with results obtained using standard analytical methodologies.