Determination of plutonium concentration and its isotopic ratio in environmental materials by ICP-MS after separation using and extraction chromatography

Abstract

An analysis method for ²³⁹ Pu and ²⁴⁰ Pu in environmental samples (including four certified reference materials) by ICP-MS was studied. Two types of chromatographic resin, Dowex 1X8 and TEVA, were examined for their applicability to the separation of Pu from the matrix elements. Sufficient decontamination factors (10 ⁴ -10 ⁵ ) for many matrix elements including U, which interferes with the detection of mass 239, were obtained with both resins. The detection limit of Pu by ICP-MS was about 0.02 pg ml ^–1 (0.05 mBq ml ^–1 for ²³⁹ Pu; 0.17 mBq ml ^–1 for ²⁴⁰ Pu) in the sample solution or 0.1 pg in the sample. Analytical results of ^239+240 Pu in certified reference materials (IAEA-135, -SOIL-6, -368 and -134) indicated that the accuracy of the method was satisfactory. Data on the ²⁴⁰ Pu/ ²³⁹ Pu atom ratios in these reference materials, which are scarce in the literature, were also obtained, i.e., 0.211 for IAEA-135, 0.191 for IAEA-SOIL-6, 0.043 for IAEA-368 and 0.200 for IAEA-134. Compared with alpha-spectrometry, the ICP-MS method has significant advantages in terms of its simple analytical procedures, prompt measurement time and capability of determining the ²⁴⁰ Pu/ ²³⁹ Pu ratio.