Method for determination of Pu isotopes in soil and sediment samples by inductively coupled plasma mass spectrometry after simple chemical separation using TK200 resin

Abstract

Plutonium has been extensively studied in the environment, for the purpose of radiological assessment, environmental behavior study and nuclear emergency response. To determine Pu isotopes in environmental soil and sediment, a novel analytical method was established in this study using a new type of extraction resin, TK200 resin. Firstly an investigation was performed to study the extraction behaviors of Pu, U, Th, Hg, Tl, Pb, Bi and Hf on TK200 resin. On the basis of the results, a new chromatographic procedure was then proposed to separate Pu from the elements that interfere the accurate determination of Pu isotopes by mass spectrometry. Owing to the excellent separation efficiency between Pu and interfering elements (IEs) of the developed procedure, high decontamination factors (DFs) were obtained for IEs, e.g. the DF(U) (>7.5 × 107) was the highest reported value. The separation procedure was finally combined with HNO3 leaching, CaF2/LaF3 coprecipitation and sector field-inductively coupled plasma mass spectrometry (SF-ICPMS) measurement to establish a complete method. The established method was evaluated by analyzing four standard reference materials (soil, sediment), and the results showed that both 239+240Pu activity and 240Pu/239Pu isotopic ratio were accurately determined, with stable and high Pu chemical recoveries (81–91%). The whole analytical method only took about 15 h, and the limits of detection were calculated to be 0.13–0.24 fg g−1 for Pu isotopes (for 2 g soil or sediment), guaranteeing the rapid determination of ultra-trace level Pu in soil and sediment samples.