Accurate Determination of Plutonium in Soil by Tandem Quadrupole ICP-MS with Different Sample Preparation Methods

In this work, three commonly used digestion techniques, such as acid leaching with 8 M HNO3, aqua regia and lithium metaborate fusion, were employed to extract Pu from different types of soil samples widely found across China, and to establish the influence of the major interference elements (U, Hg, Pb, Tl, and Bi) on the accurate measurement of Pu by tandem quadrupole ICP-MS. The three sample digestion techniques yielded good results for the analysis of Pu isotopes originating from global atmospheric fallout. The U and Pb contributions to m/z=239 (2.38 and 0.3 cps) in samples digested by the fusion method using AGMP-1M resin were higher than those digested by the acid leaching methods (0.55 cps for U and < 0.03 cps for Pb), which implies that additional purification with TEVA resin would be required for low-level Pu determination in soil samples. By taking advantage of tandem quadrupole ICP-MS in the NH3/He mode, the count rates of Hg, Tl and Bi at m/z=239 (<0.01 cps) in the samples purified by using AGMP-1M resin and/or TEVA resin were found to be negligible for the different sample digestion methods.

Automated summary

This study validated the effectiveness of three commonly used sample digestion techniques in analyzing Pu isotopes from global atmospheric fallout, and found that purification using specific resins can reduce the influence of major interference elements, thereby improving the accurate measurement of Pu.