Method for ultra-trace level 241Am determination in large size soil samples by SF-ICP-MS: with emphasis on the removal of spectral interferences and matrix effect

A new analytical method using SF-ICP-MS was developed for the determination of 241Am in large soil samples to provide realistic soil-plant transfer parameter data for dose assessment of nuclear waste disposal plans. We investigated four subjects: extraction behaviors of interfering elements (Bi, Tl, Hg, Pb, Hf and Pt) on DGA-N resin; soil matrix element removal (Mg, Fe, Al, K, Na) using Fe(OH)3, CaF2 and CaC2O4 co-precipitations; Am and rare earth elements (REEs) separation on DGA-N and TEVA resins; and optimization of the Aridus II–SF-ICP-MS analytical system for Am determination. Our method utilized conc. HNO3 to leach Am from 2-20 g soil samples. The CaC2O4 co-precipitation was used to remove major metals in soil, and followed by Am/interfering elements separation using the proposed UTEVA+DGA-N procedure. After a further separation of REEs on TEVA resin, 241Am was determined by Aridus II–SF-ICP-MS. This method eliminated the matrix effect in ICP-MS 241Am measurement for large soil samples. The high decontamination factors (DFs) of interfering elements enable their thorough removal from Am fraction, and in particular, the DF of Pu (7 × 105) was the highest ever reported in 241Am studies; thus, this method is capable of analyzing 241Pu-contaminated FDNPP-sourced soil samples. A low detection limit of 0.012 mBq/g for 241Am was achieved. The chemical recovery of Am (76% -82%) was very stable for soil samples. This method can be employed for the low level 241Am determination in large size soil samples that are contaminated with 241Pu