Method for Ultratrace Level 241Am Determination in Large Soil Samples by Sector Field-Inductively Coupled Plasma Mass Spectrometry: With Emphasis on the Removal of Spectral Interferences and Matrix Effect

A new method using sector field-inductively coupled plasma mass spectrometry (SF-ICPMS) was developed for the determination of Am-241 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 resin (normal type, abbreviated as DGA-N); soil matrix element removal (Mg, Fe, Al, K, Na) using Fe(OH)(3), CaF2, and CaC2O4 coprecipitations; Am and rare earth elements (REEs) separation on DGA-N and TEVA resins; and optimization of SF-ICPMS (equipped with a high efficiency nebulizer (HEN)) for Am determination. Our method utilized concentrated HNO3 to leach Am from 2 to 20 g soil samples. The CaC2O4 coprecipitation 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, Am-241 was determined by HEN-SF-ICPMS. This method eliminated the matrix effect in ICPMS Am-241 measurement for large soil samples. The high decontamination factors (DFs) of interfering elements enable their thorough removal, and in particular, the DF of Pu (7 X 10(5)) was the highest ever reported in Am-241 studies; thus, this method is capable of analyzing Pu-241-contaminated Fukushima Daiichi Nuclear Power Plant (FDNPP) sourced soil samples. A low detection limit of 0.012 mBq g(-1) for Am-241 was achieved. The chemical recovery of Am (76-82%) was stable for soil samples. This method can be employed for the low level 241Am determination in large size soil samples that are contaminated with Pu-241.