Rapid methods for the determination of long-lived radionuclides in environmental samples by ICP-SFMS and radioanalytical techniques

Abstract

Two improved sample preparation methods for the determination of americium and plutonium (Method 1) and plutonium (Method 2) from environmental samples by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) and alpha spectrometry are presented. Both procedures involve a rapid CaF₂ co-precipitation step for pre-concentration and matrix removal followed by extraction chromatographic separations. The average recovery after sample preparation was better than 85 % for both americium and plutonium. The method developed also focused on the elimination of possible interferences in the mass spectrometric analysis caused by molecular ions (e.g. ²⁰⁸Pb¹⁶O ⁺₂ or ²³⁸U¹H⁺) by employing suitable matrix separation prior to ICP-SFMS analysis of the desolvated sample. Isotopes with alpha energies similar to the analytes that may cause interferences in alpha spectrometric analysis were also separated. For ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu and ²⁴¹Am detection limits of 15, 9.2, 14 and 23 fg g⁻¹, respectively were achieved by ICP-SFMS, and 0.1 mBq obtained by alpha spectrometry. The methods developed are especially applicable for monitoring purposes of anthropogenic transuranium elements, as the analysis (sample preparation and ICP-SFMS measurement) can be carried out within 6 hours for one batch of samples.